If symbols do not display correctly change your browser character encoding to unicode CRUISE REPORT: A12 (Updated APR 2013) HIGHLIGHTS CRUISE SUMMARY INFORMATION WOCE Section Designation A12 Expedition designation (ExpoCodes) 06AQ20080210 Chief Scientists Eberhard Fahrbach/AWI Dates 2008 Feb 10 - 2008 Apr 16 Ship R/V POLARSTERN Ports of call Cape Town, South Africa - Punta Arenas, Chile 37° 0'S Geographic Boundaries 65° 32'W 12° 45'E 70°34'S Stations 217 Floats and drifters deployed 15 NEMO, 39 APEX floats deployed Moorings deployed or recovered Grenwich meridian: 9 recovered, 5 deployed Weddell Sea: 3 recovered, 5 deployed Kapp Norvegia: 3 recovered, 8 deployed Sound sources: 5 recovered, 7 deployed PIES: 5 recovered, 5 deployed Recent Contact Information: Eberhard Fahrbach Alfred Wegener Institute • Bussestrasse 24 • D-27570 Bremerhaven • (Building F-214) Tel: +49(471)4831-1820 • Fax: +49(471)4831-1797 Email: Eberhard.Fahrbach@awi.de The Expedition ANT-XXIV/3 of the Research Vessel "Polarstern" in 2008 Edited by Eberhard Fahrbach and Hein de Baar with contributions of the participants Please cite or link this item using the identifier hdl:10013/epic.34050 or http://hdl.handle.net/10013/epic.34050 ISSN 1866-3192 ANT-XXIV/3 10 February - 16 April 2008 Cape Town - Punta Arenas Weddell Sea, Drake Passage Chief Scientist: Eberhard Fahrbach Koordinator / Coordinator Eberhard Fahrbach This report is dedicated to Willem Polman and Stefan Winter who lost their lives by the helicopter accident at the Neumayer Station on 2 March 2008. CONTENTS 1. EXPEDITION ANT-XXIV/3: Fahrtverlauf und Zusammenfassung Itinerary and summary 2. CASO - (Climate of Antarctica and the Southern Ocean) 2.1 Decadal variations of water mass properties in the Atlantic sector 2.2 Transport variations of the Antarctic Circumpolar Current 2.3 Monitoring the ACC transport through Drake Passage 2.4 Measurements of trace gases: chlorofluorocarbons, helium isotopes & neon 2.5 Oxygen measurements 3. GEOTRACES in the International Polar Year during ANT-XXIV/3 expedition 3.1 Trace elements during ANT-XXIV/3 expedition: NIOZ team 3.2 Trace elements during ANT-XXIV/3 expedition: IFM-GEOMAR team 3.3 Isotopes by the AWI-TEAM 3.4 Nutrient measurements during ANT-XXIV/3 3.5 Silicate measurements with cyclic voltammetry 3.6 Intercomparison of GEOTRACES variables with BONUS-GOODHOPE 4. Dissolved carbon dioxide in the Southern Ocean 4.1 Deep-ocean carbondioxide chemistry (DIC, TAlk) 4.2 Surface water carbondioxide chemistry (DIC, pCO2) 4.3 Intercomparison of carbondioxide variables with BONUS-GOODHOPE 5. Marine biology 5.1 The significance of viruses for polar marine ecosystem functioning 5.2 Phytoplankton measurements 6. Automatic detection of marine mammals 7. Weather situation during the cruise leg ANT-XXIV/3 8. Acknowledgement APPENDIX A.1 Beteiligte Institute/Participating Institutes ANT-XXIV/3 A.2 Fahrteilnehmer/Participants A.3 Schiffsbesatzung/Ship's crew A.4 Stationsliste /station list PS71 1. EXPEDITION ANT-XXIV/3: FAHRTVERLAUF UND ZUSAMMENFASSUNG Eberhard Fahrbach(1), (1)AIfred-Wegener-Institut, Bremerhaven Hein de Baar(2) (2)NIOZ Von Kapstadt zur Neumayer-Station Die Reise sollte am 6. Februar 2008 in Kapstadt beginnen. Der Hafenaufenthalt stand im Zeichen des Besuchs der Bundesministerin für Bildung und Forschung Frau Dr. Annette Schavan. Sie kam mit südafrikanischen Ministerkollegen, Würdenträgern und Wissenschaftlern sowie unseren Kollegen vom französischen Forschungsschiff Marion Dufresne zu Gesprächen, einem Workshop und einem gelungenen Empfang an Bord. Das Ereignis war sorgfältig vorbereitet worden und die gute Stimmung der 150 Gäste war ein sicheres Zeichen für den Erfolg dieser Bemühungen. Der anhaltend stürmische Wind verhinderte, dass ein noch aus stehender CO2Container in Kapstadt angelandet werden konnte. Schließlich wurde das Schiff mit unserem Container nach Port Elizabeth umgeleitet, und so traf er erst in der Nacht zum 10. Februar auf der Polarstern ein. Unverzüglich wurde seeklar gemacht und so begann unsere Reise am 10. Februar endlich mit dreieinhalb Tagen Verspätung. Die Fahrtroute ist in Abb. 1.1 dargestellt. Als Erstes wurden die Messungen vom fahrenden Schiff aus aufgenommen. Der akustische, profilierende Strömungsmesser (Akustischer-Doppler- Profilstrommesser, ADCP) und der Thermosalinograph lieferten Daten und die Pumpen förderten Wasser für Analysen. Entweder durch einen Schnorchel im Kiel in das bordeigene Leitungsnetz oder, um besonders reines Wasser zu erhalten, aus einem Schleppfisch, der Wasser neben dem Schiff einsaugte. Die erste Station diente zur Aufnahme eines sogenannten PIES (Pressure Inverted Echosounder), der an dieser Position verankert war und die Schwankungen der Meeresoberfläche und der Schallgeschwindigkeit in der Wassersäule erfasst hat. Nach Abschluss der Aufnahme begann eine Station zur Erprobung eines Wasserbeprobungssystems, der sogenannten Ultraclean-CTD, die besonders dafür ausgelegt ist, Wasserproben zu nehmen, um die Konzentration des im Ozean gelösten Eisens zu bestimmen. Die Messung minimaler Konzentrationen von Eisen im Meerwasser stellt unvorstellbare Ansprüche an die Probennahme, da das Schiff überwiegend aus Eisen besteht. Um diesen Einfluss des Schiffes zu vermeiden, wurde im Niederländischen Meeresforschungsinstitut (NIOZ) ein spezieller Probennehmer gebaut. Er besteht aus Titan und wird an einem Keviardraht gefiert, um alles Eisen im Bereich der Probennahme zu vermeiden. Zur Erfüllung dieser hohen Anforderungen entstand ein System aus Winde, Stromversorgung und ReinraumContainer, das das Arbeitsdeck nahezu ausfüllt. Der Test verlief erfolgreich. Am 11. Februar 2008 kreuzte sich unser Kurs mit dem des norwegischen Forschungsschiffes G.O. Sars, das auf dem Weg nach Kapstadt war und sein Programm beendet hafte. Zwei deutsche Kollegen waren an Bord. Obwohl wir an einem gemeinsamen Programm mit im Ozean verankerten PIES arbeiten, musste sich das Treffen auf ein Winken von Schiff zu Schiff, dem Blasen der Hörner und dem anschließenden Austausch von Fotos per Email beschränken, da wir bei der gegebenen Verzögerung keine weitere Zeit verlieren wollten. Die nächste Teststation galt dem Hauptarbeitsmiftel der Ozeanographen, der CTD (Conductivity, Temperature, Depth), die uns die Vertikalverteilung von Temperatur, Salzgehalt, Sauerstoff, Trübung und Fluoreszenz an Bord anzeigt. Zusätzlich wurde das Strömungsprofil mit zwei Akustischen-Doppler-Profilstrommessern (ADCP) erfasst, die an der CTD befestigt waren. Auch hier war der Erfolg zu vermelden, so dass die Probestation schon für die Forschung verwendbares Wasser und Daten lieferte und man zu Routine übergehen konnte. Diese wurde allerdings durch das Wetter unterbrochen, da uns ein Tief mit 10 Windstärken streifte und unseren Weg nach Süden verzögerte. Am 15. Februar überquerten wir die ozeanische Polarfront und am 25. Februar den 60. Breitengrad. Damit erreichten wir die Antarktis und das nördliche Stromband des Weddellwirbels. Dieses großräumige, nierenförmige Strömungssystem füllt den gesamten antarktischen Sektor des Atlantiks aus. Östlich des Meridians von Greenwich strömt warmes, salzreiches Wasser aus dem Antarktischen Zirkumpolarstrom, das Zirkumpolare Tiefenwasser, nach Süden. Im Westen fließt in der Tiefe das neu gebildete Weddeilmeer-Bodenwasser nach Norden. Im Süden folgt der Antarktische Küstenstrom als südlicher Randstrom dieses Wirbels dem Verlauf des Kontinentalabhangs und der Schelfeiskante. Die Lufttemperaturen sanken auf etwas über 0°C mit leichtem Schneefall. Der Wind pendelte zwischen 6 und 8 Windstärken hin und her. Zahlreiche Eisberge trieben im nördlichen Stromband des Weddellwirbels von der Antarktischen Halbinsel in unseren Bereich. Allerdings waren es nur stark verwitterte Reste und nicht die für die Antarktis typischen Tafeleisberge. Der Stationsabstand von anfänglich 100 Seemeilen wurde auf 30 Seemeilen verringert, da unser Hauptarbeitsgebiet im Weddellwirbel lag. Der nördliche Teil des Schnitts wurde von der Marion Dufresne abgedeckt. An jeder Station wurde eine CTD-Sonde eingesetzt. An sogenannten "Superstationen" kam das ganze Spektrum der Probennahme zum Einsatz. Auf dem Meridian von Greenwich führten wir 7 dieser Superstationen durch, bei denen in mehrfacher Folge mit dem Kranzwasserschöpfer, dem Ultraclean-CTD und den in-situ Pumpen Wasserproben für die GEOTRACESProbennahme genommen wurden, was etwa 20 Stunden dauerte. Die Spurenstoff (GEOTRACES) - Gruppe befasste sich hauptsächlich mit der Messung von im Meerwasser gelösten Spurenmetallen. Dazu zählt das Eisen, das für den Ablauf biologischer Prozesse von besonderer Bedeutung ist. Es wird von allen lebenden Organismen benötigt und damit auch von Algen, die wiederum die Grundlage der Nahrungskette im antarktischen Ozean darstellen. Allerdings ist Eisen nur in äußerst geringen Konzentrationen von etwa einem Hundertstel von einem Millionstel Gramm in einem Liter Meerwasser (10 Nanogramm pro Liter = 10 ng/L = 10(^-8) Gramm pro Liter) vorhanden. Im Gegensatz dazu ist das Schiff Polarstern eine unvorstellbare Konzentration von Eisen und die Probennahme zur Messung der Eisenkonzentration im Meerwasser benötigt einen "ultra-reinen" Probennehmer mit 24 Schöpfern. Wenn dieses Gerät zurück an Deck ist, wird es sofort in einen ultrareinen Container gebracht, um jede Berührung mit dem Eisen des Schiffs zu vermeiden. Damit ist es erstmals möglich, vollständige Vertikalschnitte bis in 5 Kilometer Tiefe im Südlichen Ozean zu vermessen. Auf dem Meridian von Greenwich fanden wir sehr geringe Eisenkonzentrationen von nur 5 ng/L im Oberflächenwasser, die auf 30 ng/L in größerer Tiefe zunahmen. Im südlichen Teil des Schnittes zwischen der Maudkuppe und der Schelfeiskante waren die Werte (sogar) mit 3 ng/L im Oberflächenwasser und 20 ng/L in der Tiefe sogar noch geringer. Kennt man erst einmal die auch geringen Konzentrationen, so stellt sich die Frage, woher dieses Eisen überhaupt kommt? Wurde es durch Stürme, die Staub aufwirbeln, vom Land ins Meer eingetragen? Alle Böden an Land enthalten viel natürliches Eisen. Der Anteil von Eisen in den Böden beträgt etwa 4 %. Da Böden auch reichlich Aluminium (Al) enthalten, messen wir Aluminium als Nachweis für den Staubeintrag. Die Konzentrationen des im Meerwasser gelösten Aluminiums waren auf dem Schnitt entlang dem Meridian von Greenwich sehr gering. Es waren die geringsten Konzentrationen, die man bisher im Ozean fand. Diese geringen Konzentrationen von 6 ng/L im Oberflächenwasser sagen uns, dass der Staubbeitrag, wenn es ihn überhaupt gibt, sehr gering ist. Daher muss das Eisen also von einer anderen Quelle stammen. Im Sediment sind die Bedingungen günstiger, das Eisen von den Teilchen zu lösen, mit denen es in den Ozean eingebracht wurde. Also könnte dort die Quelle des Eisens im Meerwasser liegen. Wir wissen von einem anderen Element, Mangan (Mn), dass es ebenfalls in den Sedimenten gelöst werden kann. Also nutzen wir Mangan als Hinweis darauf, dass das Eisen aus dem Sediment stammt. Aber auch die Konzentrationen des gelösten Mangans sind äußerst gering, zwischen 3 ng/L im Oberflächenwasser und in etwa 10 ng/L in den tieferen Schichten. Nur über den mittelozeanischen Rücken findet man im tiefen Ozean höhere Mangan- und Eisenkonzentrationen, die durch unterseeischen Vulkanismus hervorgerufen werden. Dies lässt vermuten, der unterseeische Vulkanismus könne eine der bedeutendsten Quelle für Eisen in der Tiefsee sein. Aber auch weitere Metalle, (wie z. B. Zink) werden untersucht. So sind zum Beispiel Zink und Kupfer für Lebewesen von größter Bedeutung und auch sie kommen nur in ganz geringen Konzentrationen vor. Auf der Strecke wurden vertikal-profilierenden Driftkörper (Argo- Floats) ausgelegt. Ein großer Teil der Floats wurden von Stephen Riser von der Universität von Washington zur Verfügung gestellt. Sie sollen im Antarktischen Zirkumpolarstrom in den Indischen Ozean driften. In diesem Gebiet haben wir auch eine Serie von 6 Bodendruckmessern mit nach oben gerichteten Echoloten (PIES) aufgenommen und 5 davon wieder ausgelegt. Leider ging ein Gerät bei der Aufnahme verloren. Aus den Messungen dieser Geräte können die Schwankungen des Antarktischen Zirkumpolarstroms abgeleitet werden. Die Verankerungsarbeiten begannen mit der erfolgreichen Aufnahme von drei Verankerungen im Übergangsgebiet zwischen dem Zirkumpolarstrom und dem Weddellwirbel, mit denen der Austausch zwischen diesen Strömungssystemen erfasst wurde. Leider war aus finanziellen Gründen eine Neuauslegung dieser Geräte nicht mehr möglich. Der Unfall Am 2. März erreichten wir die Atkabucht am frühen Sonntagmorgen, nachdem wir am 28. Februar unser Arbeitsgebiet am Meridian von Greenwich verlassen haften. Nach grauen und zum Teil stürmischen Tagen wurden wir mit Sonntagswetter im wörtlichsten Sinne empfangen. Alle freuten sich darauf, nach Tagen der anstrengenden Stationsroutine, einen Tag auf dem Eis mit all den Eindrücken zu genießen, die Antarktisforschung so besonders faszinierend machen. Zwar mussten die Wissenschaftler sich darauf einstellen, auch bei den Lade- und Pumparbeiten mit Hand anzulegen, doch sollte genügend Zeit bleiben, sich am Aufenthalt auf dem Eis zu erfreuen. Als wir um 8:30 Uhr die Nachricht erhielten, dass ein Helikopter beim Personentransport zur Neumayer-Station abgestürzt war, verwandelte sich Vorfreude und Erwartung in Bestürzung und Trauer. Schnell erreichten die Hilfsmannschaften von der Neumayer-Ill-Baustelle und der Neumayer- Station die Absturzstelle und mussten den Tod eines unserer Kollegen, Willem Polman aus dem NIOZ und des Piloten Stefan Winter vermelden. Zwei weitere Insassen, Alice Renault und Maarten Klunder waren schwer und der Helikopter-Techniker Carsten Möllendorf leicht verletzt. Trotz seiner Verletzungen war es Carsten Möllendorf gelungen, die anderen Verletzten aus dem Helikopter zu bergen und per Funk Hilfe anzufordern. Wir bewundern seine Umsicht und Besonnenheit. Die Verletzten wurden so schnell wie möglich mit dem zweiten Helikopter in das Hospital der Polarstern gebracht und dort versorgt. Sofort wurde im AWI ein Krisenstab eingesetzt, der eine umfassende Unterstützungsaktion einleitete und die Information der Angehörigen und der Öffentlichkeit sowie den Rücktransport der Verletzten und Verstorbenen in beispielhafter internationaler Zusammenarbeit organisierte. An Bord haben wir uns am 3. Februar zu einer Trauerfeier auf dem Helikopterdeck versammelt und von den beiden Kollegen Abschied genommen. Willem Polman und Stefan Winter verloren ihr Leben beim schwersten Unfall, den wir während des 25jährigen Einsatzes der Polarstern zu beklagen haben. Mit dieser Feier wollten wir den Angehörigen der Opfer unser tiefes Mitgefühl ausdrücken, uns gegenseitig Trost geben, und unsere hohe Wertschätzung der beiden Opfer bekunden. Unermesslich sind der Schmerz, der Verlust und die Ängste der betroffenen Familien, bei denen wir immer mit unseren Gedanken waren. Eine Flut von Beileidsbekundungen traf aus der ganzen Welt an Bord, im AWI und im NIOZ ein. Wir möchten uns auch auf diesem Wege für das weltweite Mitgefühl bedanken, das uns die Stärke verliehen hat, diese schwierige Situation durchzustehen. Wir möchten uns auch bei allen bedanken, die dazu beigetragen haben, dass die Verletzten schnell gefunden, geborgen und behandelt werden konnten und dass unsere verstorbenen Kollegen ihre letzte Reise in die Heimat in Würde antreten konnten. Weiterhin möchten wir all denen danken, die in vielfältiger Weise dazu beigetragen haben, dass die Verletzten optimal versorgt wurden und nach Kapstadt und in die Heimat gebracht wurden. Nur wer vor Ort war, kann wirklich empfinden, welche Leistung die Stationsmannschaften von Neumayer und der Baustelle, Besatzungsmitglieder der Polarstern, Piloten, medizinisches Personal, Meteorologen, Logistiker und Organisatoren vollbracht haben, um das Ausmaß der Katastrophe zu begrenzen. Am 4. März nahmen wir noch einmal im kleinsten Kreise der unmittelbar Betroffenen an der Unfallstelle Abschied von den Opfern. Die Baumannschaft hafte zwei Kreuze am Unfallort errichtet. Als wir uns dort zum Stillen Gedenken trafen, erhob sich die Basler BT-67 mit den Särgen an Bord über unsere Köpfe hinweg zum Flug nach Novolazarevskaja, von wo aus der Weitertransport nach Kapstadt erfolgte. Als Abschiedsgruß neigten die Piloten die Tragflächen zu den Kreuzen hin. Ein würdigerer Abschied eines Polarforschers in die andere Welt lässt sich kaum vorstellen. Am 5. März erfolgte der Transport der Verletzten nach Kapstadt. Am frühen Morgen erschien die Wetterlage hoffnungslos. Es herrschte Schneetreiben. Die Verletzten mussten einer Geduldsprobe entgegen sehen. Doch dann erreichte uns die Mitteilung der Meteorologen: es werde besser und die Basler sei von Novolazarevskaja gestartet. Wir bewundern den Mut der Piloten und die Kompetenz der Meteorologen, denn es wurde besser. Bei Schneefall startete ein Transport mit Pistenbullies vom Schiff zum Flugfeld. Mit Schmerz über die Trennung und Freude über die Aussicht, diese bald in Kapstadt und bei ihren Verwandten zu wissen, nahmen wir von den Verletzten Abschied. Die Piloten nutzten die kurze Phase der Wetterbesserung, landeten, nahmen die Verletzten an Bord und starteten im letzten Moment, bevor die Bedingungen einen Flug nicht mehr zugelassen hätten. Als uns der erfolgreiche Start gemeldet wurde, legten wir von der Schelfeiskante ab, und nahmen in der Atkabucht die Forschung wieder auf. Die Ironie des Schicksals bescherte uns bei unserer Fahrt durch die Atkabucht einen sonnigen Nachmittag mit den stimmungsvollen Eindrücken, die für die Antarktis typisch sind. Schönheit und Zauber standen in unmittelbarer Nähe von Schrecken und Trauer. Der entschlossene Wille, unsere Arbeit im Sinne und zum Gedenken an unsere umgekommenen Kollegen fortzusetzen, half uns, unseren Schmerz zu überwinden und wieder zur Forschungsroutine zurück zu finden. Unser Aufenthalt an der Station diente der Versorgung. Wir haben vor allem Treibstoff und Verpflegung angeliefert. Gleichzeitig haben wir aber auch die wertvollen Eiskerne, die an der Kohnen-Station erbohrt wurden, gebrauchtes Material und Abfall an Bord genommen. Ferner mussten Container an Bord umgestaut werden, um wieder Platz zu schaffen und Material zur Verfügung zu haben, das erst während des folgenden Teils der Reise benötigt wurde. Dazu mussten Frachtcontainer von der Ladeluke auf das Eis gestellt werden, die Luken geöffnet und Laborcontainer aus den Laderäumen herausgepackt werden. Nachdem alles auf Schliffen auf dem Eis stand, um es aus dem Ladebereich auf dem Eis entfernen zu können, wurde es in neuer Folge mitsamt der zusätzlichen Fracht wieder herangefahren und eingeladen. Ein Verschiebebahnhof auf dem Schelfeis. Gleichzeitig wurde Treibstoff in Tankcontainer umgepumpt. Das gute Wetter erleichterte die Arbeiten, die zügig voran gingen. Nach Abschluss der Bergungs- und Ladearbeiten nahmen wir die Einladung des Stationsleiters gerne an, die Neumayer-Station zu besuchen und einen Eindruck von der Arbeit der Uberwinterer zu gewinnen. Sie erklärten geduldig die Eigenschaften und die Funktion der Station. Die Verabschiedung der Uberwinterer erfolgte dieses Mal mit einem kurzen Innehalten an der Station. Der Abschluss der Arbeiten am Meridian von Greenwich Eine längere Phase mit relativ schwachem Wind begünstigte den Fortschritt der Arbeiten auf dem Greenwich Meridian. Mit 7 "Superstationen" im Rahmen des G EOTRACES-Programmes, 25 U ltraclean- CTD5 und 73 "normalen" CTD-Profilen haben wir alle hydrographischen Regionen auf dem Meridian von Greenwich zufriedenstellend mit allen geplanten Parametern erfasst. Wir haben 9 Verankerungen aufgenommen und 5 wieder ausgelegt. Das Netz der vertikal profilierenden Driftkörper wurde um 38 Floats erweitert. Bei der Aufnahme der letzten Verankerung etwa 12 Meilen vor der Kante des FimbulSchelfeises wurden wir auf eine besondere Probe gestellt. Als wir versuchten mit dem POSIDON IA-System Kontakt zu den akustischen Auslösern aufzunehmen, erhielten wir keinerlei Rückmeldung. Also lösten wir blind aus und warteten ab. Doch keiner der Auftriebskörper erschien an der Oberfläche. Auch der Funkpeiler, der Signale von einem Satellitensender empfangen sollte, der an der Spitze der Verankerung sitzt, empfing nichts. Wir begannen mit dem Schiff Suchkurse zu fahren und schickten den Helikopter los. Kein Erfolg. Als uns klar war, dass die Verankerung nicht mehr vor Ort sein konnte, nahmen wir die Arbeiten mit CTD und Wasserprobennahme wieder auf und arbeiteten uns weiter nach Süden vor. Doch dann kam die große Überraschung von OPTIMARE aus Bremerhaven. Dort werden die Signale der Satellitensender Tag und Nacht überwacht. Wir erhielten die Meldung, dass der Sender kurz nach der Auslösung aufgetaucht sei, allerdings 9 km von der Sollposition entfernt. Sofort kehrten wir um, der Helikopter stieg auf und konnte wenig später die genaue Position der Verankerung in einem Eisfeld in wenigen Seemeilen Entfernung melden. Mit der genauen Position ging es dann schnell. Die Verankerung wurde vollständig geborgen. Sie zeigte Beschädigungen, die klar erkennen ließen, dass sie von einem Eisberg verschleppt worden sein musste. Dadurch lag sie in einer Entfernung von der Sollposition, in der unser akustisches Signal zwar stark genug war, um die Auslöser zu aktivieren, das schwächere Bestätigungssignal des Auslösers uns aber nicht mehr erreichte. Der Satellitensender war so tief in den Auftriebskörper hineingedrückt, dass er in Bodennähe durch die Eisfelder abgeschattet war. Er konnte aber vom Satelliten mit dem Blick von oben erkannt werden. Wir sind glücklich über den guten Ausgang. Allerdings sind beim Verschleppen durch den Eisberg am Eisecholot solche Schäden aufgetreten, dass die aufgezeichneten Daten verloren gingen. Am 12. März waren die Arbeiten am Meridian von Greenwich beendet und wir dampften in Richtung Weddell meer. Die vorläufige Betrachtung der hydrographischen Aufnahme zeigt, dass die Abkühlung des Warmen Tiefenwasser nach einer früheren Erwärmung zu Ende ist, und es sich gegenwärtig wieder erwärmt. Es handelt sich also um eine dekadische Fluktuation. Wir können jetzt das Verhalten der atmosphärischen Antriebskräfte mit dem in den 8üziger Jahren vergleichen, um damit eine Erklärung der Antriebsmechanismen dieser Veränderungen zu finden. Die Temperatur und der Salzgehalt des Weddellmeer-Bodenwassers haben in den letzten drei Jahren weiter zugenommen. Damit setzt sich eine Entwicklung, die wir seit der Mitte der Neunziger Jahre beobachten, weiter fort und die Frage stellt sich noch klarer: Hat die globale Erwärmung die Tiefsee erreicht, oder handelt es sich um eine Fluktuation über den Zeitraum von Jahrzehnten? Da von unseren australischen Kollegen berichtet wird, dass der Salzgehalt des Bodenwassers im Rossmeer und vor dem Adelieland weiter abnimmt, fordert auch dieser Gegensatz eine Erklärung, die wir im westlichen Weddellmeer gefunden haben. Im Weddelimeer Die Eisverhältnisse im östlichen Weddellmeer waren durch eine ausgeprägte Meereiszunge geprägt. Da aufgrund der Ereignisse bei der Neumayer-Station Zeit eingespart werden musste, wurde der östliche Teil des Schnitts von Kapp Norvegia nach Joinville Island aufgegeben. Alternativ war geplant, die Zunge nördlich zu umfahren, um durch im Vergleich zum Stationsbetrieb zügiges Fahren Zeit zu gewinnen. Doch die Aussicht auf sehr schlechtes Wetter führte zur Entscheidung, doch in die Zunge einzudringen. Es stellte sich heraus, dass das Eis sehr leicht war, und wir so gut vorankamen, dass wir uns am 14. März entschieden, nach Süden abzudrehen, um noch einen größeren Teil des Schnittes abdecken können. Doch bald wurde das Eis sehr schwer befahrbar, so dass wir diesen Plan nur zu einem kleinen Teil umsetzen konnten. Der Stationsabstand musste auf 45 sm vergrößert werden. Die erste Station auf dem Schnitt erfolgt am 15. März bei 69°22'S 16'21'W. Am 18. März fand die Beerdigung von Willem Polman und am 19. März die Trauerfeier für Stefan Winter staff. Gleichzeitig mit den Feiern an Land stellten wir an Bord die Forschungsarbeiten ein und trafen uns zum gemeinsamen Gedenken. Auch wenn es schwer fiel, den Schmerz zu überwinden, so gingen die Forschungsarbeiten weiter. Die tiefen Lücken, die die Verstorbenen und die Verletzen in unseren Herzen und bei der Arbeit hinterlassen haben, wurden, so gut es ging, überbrückt. So wurde aus einem Helikoptertechniker ein Windenfahrer für die Ultraclean-CTD. Mit Solidarität und noch weiter verstärkter Anstrengung wurde das Programm im Sinne und zur Würdigung der Verstorbenen fortgeführt. Wie auf dem Meridian von Greenwich war das Programm von der Routine des Fierens und Hievens der "normalen" und der Ultraclean-CTD und der Aufarbeitung des nicht versiegenden Stroms von Probenwasser geprägt. Meist gingen die Profile bis zum Meeresboden, häufig wurden aber auch kurze Profile (200 bis 300 m) eingefügt, um große Mengen Wasser zu Experimenten oder zur Extraktion der untersuchten Spurenstoffe zu erhalten. Eine besondere Herausforderung stellten immer wieder die Verankerungen dar, die wir aufnahmen und auslegten. Für unser Programm spielte die Auslegung von Schallquellen eine besondere Rolle. Um Messungen im Winter und auch unter dem Eis zu bekommen, wurden Driftkörper entwickelt, die in der Tiefe von 800 m ihre Bahnen ziehen. Nach jeweils 10 Tagen tauchen sie zuerst auf 2000 m Tiefe ab und steigen dann an die Oberfläche auf, wobei sie ein Temperatur- und Salzgehaltsprofil messen. Dort angekommen erfahren sie mit Satellitennavigation ihren Ort und geben die Messdaten ab. Soweit das weltweite Argo-System, in dessen Rahmen etwa 3000 derartiger Floats im offenen Ozean unterwegs sind, und zu dem auch wir unseren Beitrag leisten. Unter dem Eis funktioniert dieses Verfahren aber nicht, da die Floats die Oberfläche nicht erreichen können. Deshalb orientieren sich unsere Floats mit Hilfe von Schallquellen und der Laufzeit, der von ihnen ausgestrahlten Signale. Befinden sich die Floats unter dem Eis, so erkennen sie dies, da sich die Wassertemperatur in der Nähe des Gefrierpunkts bewegt, und brechen den Aufstieg an die Oberfläche ab. Erreichen sie das nächste Mal offenes Wasser, so geben sie den gesamten gemessenen Datensatz ab. Leider mussten wir feststellen, dass zwei von den aufgenommenen Schallquellen defekt waren und deshalb ihre Funktion nicht erfüllt hatten. Bei zwei Verankerungen, die wir aufgenommen haben, wurden wir mit einem besonderen Phänomen konfrontiert. Um die Verankerungsleine mit den Geräten senkrecht im Wasser zu halten, sind Auftriebskörper daran befestigt, die in der Tiefsee aus Glaskugeln in Plastikhalterungen bestehen. Nun haben wir bei den beiden letzten Verankerungen von den tiefsten Auftriebskörpern nur noch mit Glasbrei gefüllte, zerfetzte Plastikhüllen vorgefunden. Diese Reste sind eine eindrucksvolle Darstellung der Wirkung des Wasserdrucks nach einer Implosion der Glaskugeln in über 4500 m Tiefe. Das Rätseln über die Gründe ist allerdings noch nicht abgeschlossen. Im westlichen Teil des Weddellmeeres fanden wir ebenfalls wesentlich härtere Eisverhältnisse vor als erwartet. Deshalb wurden wir, was den Abschluss des Schnittes anbetrifft auf erhebliche Geduldsproben gestellt. Die Eisbedingungen im Weddeilmeer sind in diesem Sommer ungewöhnlich hart. Während des Sommers haben sich zwei große Eiszungen aus dem südlichen ins nordöstliche und nordwestliche Weddellmeer gehalten. Damit wurde ein Trend deutlich bestätigt, gemäß dem das Meereis in der Antarktis im Sommer über die letzten Jahrzehnte zugenommen hat. Allerdings bedeutet das keine wirkliche Zunahme der Eisbedeckung, sondern nur ein geringeres Abschmelzen im Sommer. Im Winter blieb die Eisdecke nahezu konstant. Für uns folgte aus dieser Entwicklung nicht nur die Frage nach einer Erklärung, sondern sie hafte auch direkte Konsequenzen für den Fahrtverlauf. Die herbstliche Eisbildung bescherte uns unerwartet schwere Eisverhältnisse, die eher für den Winter typisch sind. Schwere Eisverhältnisse bedeuten langsamere Fahrt und damit Zeitverlust im Vergleich zu einer Planung, die von mittleren Eisverhältnissen ausgegangen war. Dieser Zeitverlust musste durch die Reduktion von Stationszeit ausgeglichen werden. Sie erfolgte durch die Vergrößerung des Stationsabstands und damit der Fehlergrenzen bei der Abschätzung längerfristiger Veränderungen. Trotzdem gelang es, die dominierenden Wassermassen so ausreichend zu erfassen, dass der Anschluss an die Veränderungen, die wir auf dem Meridian von Greenwich gesehen haften, gefunden werden konnte. Der Gehalt von Spurenstoffen ist in bisher nicht erreichter Qualität erfasst worden. Eine besondere Herausforderung stellte die Aufnahme von Verankerungen bei schweren Eisverhältnissen dar. Bei der letzten Verankerung, die wir im Weddellmeer aufzunehmen hatten, führte das Zusammentreffen von hoher Professionalität, die sich mit der Erfahrung von Jahrzehnten (25 Jahre Polarstern) gebildet hat und dem Quäntchen Glück, dass man immer braucht, um erfolgreich zu sein, zur glücklichen Aufnahme bei fast 100 % Eisbedeckung. Da die Verankerungen schon drei Jahre lagen und die nächste Möglichkeit erst wieder in 3 Jahren bestanden hätte (wenn die Batterien der Auslöser erschöpft sein würden), gab es keine wirkliche Alternative, als den Versuch zu wagen. Der Erfolg erfüllte uns alle mit Freude und auch Stolz. Damit konnten wir die Bilanz ziehen, dass nach der erstmaligen Verankerungsdauer von 3 Jahren alle Verankerungen wieder aufgenommen werden konnten. Leider ist aber die Gerätetechnik noch nicht so ausgreift wie unsere Verankerungstechnik. Trotz 100 % Aufnahmerate liegt die Datenrate auf Grund von Geräteausfällen niedriger. Die Auswertung der Daten, die in den verankerten Geräten gespeichert wurden, begann schon an Bord. Ein erster Blick zeigte, dass die Folge von Erwärmungs- und Abkühlungsvorgängen, die wir in unseren CTD- Schnitten mit großem zeitlichem Abstand sehen, keine Zufallsergebnisse darstellen, sondern dass sie durch die dazwischen liegenden Messungen mit verankerten Geräten voll bestätigt wurden. Eine besondere Herausforderung wird nun darin bestehen, die extremen Eisverhältnisse in Beziehung zu den Wassermasseneigenschaften zu setzen, die neben den atmosphärischen Verhältnissen für die Veränderungen verantwortlich sein können. Am 29. März wurden die Arbeiten im Weddellmeer abgeschlossen. Mit 1 "Superstation" im Rahmen des GEOTRACES-Programmes, 15 ultraclean-CTDs und 45 "normalen" CTD-Profilen haben wir das zentrale und das westliche Weddellmeer zufriedenstellend mit allen geplanten Parametern erfasst; im östlichen Weddellmeer ist leider eine Lücke geblieben. Wir haben 3 Verankerungen aufgenommen und 8wieder ausgelegt. Das Netz der vertikal profilierenden Driftkörper wurde um 16 Floats erweitert. King George Island und die Drakestraße Am 30. März erreichten wir King George Island nachdem wir an der Nordspitze der Antarktischen Halbinsel noch einmal mit schweren Eisverhältnissen zu kämpfen hatten. An der Maxwellbucht im Potter Cove liegt die argentinische Station Jubany, der das deutsche Dallmann-Labor angeschlossen ist. Von hier und von den Stationen Frei und Artigas aus sollte die Übernahme von Fracht stattfinden. Eine Gruppe von sieben französischen und einer chilenischen Wissenschaftler/innen wartete bei der russischen Station Bellingshausen und 2 koreanische Wissenschaftler bei der koreanischen Station King Sejong, um an zu Bord kommen. Ihr Interesse bestand in den Arbeiten in der Drake-Passage. Da der Flug von King George Island nach Punta Arenas gestrichen worden war, musste die Gruppe, die aussteigen wollte, um den Zusteigenden Platz zu machen, bis zum Ende der Reise an Bord bleiben. Nach einer sonnigen Anfahrt kam aber in der Bucht Nebel auf und eine Zeit des Wartens begann, bis der Flugbetrieb endlich möglich war. Nach mehreren Versuchen bei jeweils kurzfristigen Wetterverbesserungen, gelang es am 31. März die neuen Fahrtteilnehmer an Bord zu bringen und die Ladung, die bei den Stationen Jubany und Frei auf uns wartete, aufzunehmen. Wir mussten aber die Übernahme von Ladung von Artigas aufgeben. Der Nebel war zu dicht geworden und eine Wetterbesserung, die weitere Flüge ermöglicht hätte, war nicht abzusehen. In der Nacht dampften wir in die Drake-Passage und setzten die Aufnahme der hydrographischen Bedingungen und der Spurenstoffverteilung fort. Am 3. April überquerten wir 60° 5 und verließen damit die Antarktis. Im Vordergrund der Arbeiten in der Drake-Passage stand die Aufnahme und Auslegung von franzözisch/koreanischen Verankerungen. Es sollten 10 Verankerungen aufgenommen und 5 wieder ausgelegt werden. Während die ersten beiden Verankerungen der koreanischen Arbeitsgruppe in der südlichen Drake-Passage trotz sehr schlechtem Wetters erfolgreich aufgenommen werden konnten, hatten wir - trotz wesentlich besserem Wetter - große Schwierigkeiten mit den französischen Verankerungen. Bei den aufzunehmenden Verankerungen ergaben sich Probleme mit dem Auftrieb, der zum Teil dem Druck nicht stand gehalten hatte. Bei den meisten von ihnen reichte der verbleibende Auftrieb noch aus. Da sie aber zum Teil nur sehr langsam an die Oberfläche kamen, wurde viel Geduld gefordert. Beruhigend war, dass ihr Aufstieg mit POSIDONIA überwacht werden konnte. Zwei Verankerungen lösten sich zwar vom Boden, erreichten aber die Oberfläche nicht. Mit zeitaufwändigen Manövern versuchten wir zwar, sie einzufangen, indem wir etwa 5000 m Draht in Schleifen über den Grund um sie herum zogen. Aber unsere Bemühungen blieben leider ohne Erfolg. Wie immer wir unsere Schleifen legten, was bei 6 bis 7 Windstärken nicht einfach war, die driftenden Verankerungen konnten uns wieder entweichen, so dass wir beide Dredge-Aktionen enttäuscht abbrechen mussten. Die verlorene Zeit konnte nur durch die Einschränkung des CTDProgramms ausgeglichen werden. Trotzdem haben wir viel Glück gehabt, da sich die Drake-Passage mit dem berüchtigten Kap Hoorn uns gegenüber sehr zurückhaltend gezeigt hat. Richtig schlechtes Wetter sollte uns erst am 13. April erwischen. Daher beschlossen wir, nicht mehr weiter nach Süden zu fahren, um die ausgelassenen CTD-Stationen nachzuholen, sondern beendeten bei 5601,07'S 6400,59'W am 13. April mit einer letzten CTD das Forschungsprogramm und dampften vor dem Wind in Richtung Le-Maire-Straße. Mit 5 "Superstationen" im Rahmen des GEOTRACES-Programmes, 12 ultracleanCTD5 und 46 "normalen" CTD-Profilen haben wir die Drake- Passage nicht ganz zufriedenstellend mit allen geplanten Parametern erfasst. Wir haben 8 Verankerungen aufgenommen und 5 wieder ausgelegt. Das Netz der vertikal profilierenden Driftkörper wurde um 14 Floats erweitert. Am Mittwoch, dem 16. April 2008 endete die Reise plangemäß in Punta Arenas. Wissenschaftliche Hintergründe Unsere Reise war vor allem der Untersuchung der ozeanischen Zirkulation und den davon abhängenden Stoffkreisläufen mit ihrem Einfluss auf das Leben im Meer gewidmet. Das Hauptprogramm der Reise erfolgt im Rahmen des Internationalen Polarjahres 2007/2008 (IPY). Es steht unter der Schirmherrschaft der ICSU und der WMO und soll durch eine weltweite Koordination der Kräfte und die Intensivierung der Aktivitäten zu einer quasi-synoptischen Aufnahme der Bedingungen in beiden Polargebiete führen, die als Grundlage der Bewertung der gegenwärtig ablaufenden Veränderungen dienen wird. Im GEOTRACES-Projekt wurden Spurenstoffe und biogeochemische Prozesse untersucht. Das CASO-Projekt (Climate of Antarctica and the Southern Ocean) setzte Arbeiten des früheren WECCON- Projekts (Weddell Sea Convection CONtrol) fort. Es begann mit dem World Ocean Circulation Experiment (WOCE) als von 1989 bis 2001 Untersuchungen im Weddellmeer ausgeführt wurden, die zum besseren Verständnis der Wassermassentransformation und Zirkulation beigetragen haben. Diese Messungen wurden anschließend im Climate Variability and Predictability (CLIVAR) Programm des World Climate Research Programme (WCRP) der UNESCO fortgesetzt. Die Arbeiten in der Drake-Passage erfolgten im Rahmen des französischen DRAKE-Projekts, das ebenfalls ein Beitrag zum IPYProjekt CASO ist. Die globale Bedeutung der regionalen Prozesse wird im IPYProjekt BIAC (Bipolar Atlantic Thermohaline Circulation) berücksichtigt. Im Norden schließen die Messungen an die Arbeiten des BONUS-GOODHOPE-Projektes an. Die Untersuchungen bei der Maudkuppe und im Antarktischen Küstenstrom fanden im Rahmen des von SCOR (Scientific Committee of Oceanographic Research) betreuten iAnzone Programms statt, das einen Beitrag zum Climate and Cryosphere (CLIC) Programm des WCRP liefert und im IPY mit dem Projekt SASSI Synoptic Antarctic Shelf Slope Interactions Study vertreten ist. In diesem Programm ist besonders die Ausbringung der Upward Looking Sonars (ULS) und der Verankerungen an der Küste von Bedeutung. Die ULS sind ein Beitrag zum Antarctic Sea Ice Thickness Projects (AnSITP). Das Ausbringen der Floats erfolgte im Rahmen des internationalen Argo-Programms, das zum Gobal Ocean Observing System (GOOS) beiträgt. Im Rahmen der internationalen Programme erfolgt besonders enge Zusammenarbeit mit dem Bjerknes Centre in Bergen, Norwegen, und dem British Antarctic Survey (BAS), der am Verankerungsprogramm beteiligt ist. Die gesamte Expedition ist ein Beitrag zum MARCOPOLI-Programm der Hermann von HelmholtzGemeinschaft Deutscher Forschungszentren (HGF). Ziel der Reise war es, Meeresströmungen und die Temperatur-, Salzgehalts- und Spurenstoffverteilungen im Südlichen Ozean zu erfassen. Die Absinkbewegungen im Südlichen Ozean stellen den südlichen Teil der globalen Umwälzbewegung im Ozean dar. Sie bestimmen seine Rolle im Klimageschehen und sind für den Spurenstoffkreislauf von Bedeutung. Unsere Messungen werfen die Frage auf, ob die tief reichende Umwälzbewegung der ozeanischen Wassermassen in der Antarktis nach einer Phase der Schwächung wieder zunimmt. Seit mehr als einem Jahrzehnt konnte beobachtet werden, dass die Temperatur in der Tiefsee im Weddellmeer kontinuierlich zunahm, was darauf schließen ließ, dass die tief reichenden Absinkbewegungen am Rand der Antarktis abgenommen haben. Nun sinken die Temperaturen wieder. Diese Entwicklung der Wassermassen erfolgt zu einer Zeit, zu der das Meereis in der Antarktis im Sommer zunimmt. Dies macht deutlich, dass der Einfluss der globalen Erwärmung vor dem Hintergrund jahrzehntelanger Schwankungen nicht eindeutig zu identifizieren ist. Besondere Aufmerksamkeit erregt die Tatsache, dass nach Auswertungen von Satellitenaufnahmen durch das NSIDC klar geworden ist, dass der Antarktische Sommer 2007/2008 der eisreichste Sommer war, den es seit dem Beginn der Satellitenaufnahmen gab. Dieser Trend, der im atlantischen Teil des Südlichen Ozeans besonders ausgeprägt ist, steht im Gegensatz zur Entwicklung in der Arktis, wo eine deutliche Abnahme des Meereises im Sommer zu verzeichnen ist. Die gegensätzlichen Entwicklungen in Antarktis und Arktis zu verstehen, ist ein wesentliches Ziel dieser Reise. Da sie aber im Laufe von Jahrzehnten verlaufen und merkliche räumliche Unterschiede aufweisen, reichen die Polarstern-Reisen nicht aus, um sie mit ausreichender Sicherheit zu verfolgen. Deshalb muss eine umfassende Erfassung mit Hilfe autonomer Mess-Systeme erfolgen, die entweder verankert oder frei treibend sind. Sie stellen eine Komponente des Südlichen-OzeanObservations-Systems (SOOS) dar, das zur Zeit entwickelt wird. Als Beitrag zu diesem System wurden in internationaler Zusammenarbeit 18 verankerte Beobachtungsstationen ausgelegt und 20 geborgen. Mit 3 Jahren Einsatzdauer stellen die jetzt aufgenommenen Systeme einen Rekord auf. Mit der Auslegung von 67 Floats, von denen die im Weddellmeer ausgelegten auch unter dem Meereis Daten erfassen können und bis zu 5 Jahren aktiv bleiben, wurde ein bisher nicht erreichtes Messnetz in diesem Teil der Erde erstellt. Im Internationalen Polarjahr sollten nicht nur neue Erkenntnisse über die Rolle der Polargebiete im System Erde gewonnen werden. Es war ein zentrales Anliegen, die Öffentlichkeit und insbesondere den Nachwuchs in die aktuelle Forschung einzubeziehen und umfassend zu informieren. Aus diesem Grund waren zwei Lehrer an Bord. Sie haben aktiv an den Forschungsarbeiten teilgenommen und ihren Schülern, Kollegen und auch Zeitungen ihre Erlebnisse regelmäßig über Telefon und Internet vermittelt. Ihre Erfahrungen werden im Rahmen eines Lehrernetzwerks auch in den Unterricht weiterer Schulen und hoffentlich auch in Schulbücher einfließen. Abb. 1.1: Die Fahrtroute der Polarstern während der Reise ANT-XXIV/3 vom 6. Februar bis zum 16. April 2008 Fig. 1.1: Cruise track during Polarstern leg ANT-XXIV/3 from 6 February to 16 April 2008 ITINERARY AND SUMMARY From Cape Town to Neumayer Station The call to port in Cape Town was marked by a visit of the German Federal Minister of Education and Research, Dr. Annette Schavan. She came on board with South African Ministerial colleagues, dignitaries and scientists in addition to a group of our colleagues from the French research vessel Marion Dufresne. During the visit talks were held along with a workshop and a reception. The event was carefully prepared and the good mood of the 150 guests proved it as a success. We were supposed to leave on 6 February 2008, but strong winds prevented a container for the CO2 programme to arrive Cape Town in time. Then, the container ship was diverted to Port Elizabeth and the container was finally loaded onto Polarstern in the night to 10 February. We immediately prepared to depart and our journey could finally start on 10 February with three and a half days of delay. The cruise track is displayed in Fig. 1.1. Observations started with instruments which are applied from the moving ship with the acoustic profiling current meter (ADCP) and the thermosalinograph. Pumps started to inject seawater from a snorkel in the keel of the ship into the pipes to the labs for analysis and for those who need particularly clean water a fish was used to pump seawater from a certain distance onto the ship. The first stop was dedicated to recover a PIES (Pressure inverted echosounder) which moored on the sea floor recorded variations in the sea level elevation and the sound velocity in the water column. It was the first one of a set of those instruments to be recovered and moored again. Then, a test station for the ultraclean CTD followed. It was brought on board by a group from the Netherlands Institute of Sea Research (NIOZ). It was supposed to take samples which enable scientists to measure the concentration of dissolved iron in the water. It was understood that it is highly challenging to measure iron in very faint concentrations on a ship which is mainly made out of iron. To avoid interference with the ship the NIOZ group had built a special sampling system from titanium lowered with a Kevlar wire which avoids any iron parts in the vicinity of the sampling process. To meet this requirement a huge device was installed which fills up large parts of the deck consisting of a huge winch, a power station and a clean room container. The tests were successful and proved that the system was mechanically and electronically fully operational. On 11 February we crossed the course of the Norwegian research vessel G.O. Sars, which was on its way back to Cape Town from a cruise on which two German colleagues participated. In spite of having a common programme with PIES in the Southern Ocean, we had to restrict ourselves to waving the arms, blowing the horns and a subsequent email exchange of slides taken of each of us, since we could not afford to loose further time on our way to the South. The next test station aimed on the main work horse of the physical oceanographers, the CTD probe (conductivity, temperature, depth) with the rosette water sampler. It is lowered to depth to measure the vertical profiles of temperature, salinity, oxygen, transmissivity and fluorescence. The data are transmitted on board, displayed and stored. In addition a current profile is obtained from the lowered acoustic Doppler current profiler (LADCP) which is mounted on the CTD frame. Here, as well, the test was performed successfully and water samples and data could be used for the programme. Weather slowed us down when a low pressure system passed nearby providing us with winds of up to 10 Bft. In this northern part of our operation area station work and steaming alternated with a distance of almost 100 nm, weather and sea permitting. Since the focus of our work was south of the Polar Front the distance between the stations decreased to about 30 nm after we have passed this point. However, the gaps in the North were closed via cooperation with the scientists on the French research vessel Marion Dufresne whose focus was on the northern part of the region. Our cooperation in the context of the International Polar Year 2007/2008 resulted in a comprehensive survey of the sea area between South Africa and Antarctica. On 15 February we crossed the Polar Front and reached Antarctica on 25 February when crossing 60°S. We arrived at our main operation area when entering the northern limb of the Weddell gyre, the large-scale bean- shaped current system which covers the Antarctic sector of the Atlantic Ocean. East of the Greenwich meridian warm and salty water from the Antarctic Circumpolar Current, the Circumpolar Deep Water, flows to the south. In the west newly formed Weddell Sea Bottom Water returns at great depth to the north. In the south the Antarctic Coastal Current and the Antarctic Slope Current follow as the southern boundary current of the gyre the continental slope and the ice shelf front from east to west. Air temperatures decreased to near to 0°C and scattered snowfall occurred. The wind fluctuated from 6 to 8 Bft. Significant numbers of icebergs were encountered which drifted with the northern limb of the Weddell gyre from the Antarctic Peninsula into our operation area. However, so far we have only met highly weathered remnants and not the impressive table icebergs for which Antarctica is famous. At super stations a full suite of water sampling devices with at times more than 10 casts was operated including the CTD/rosette water sampler, the ultraclean sampler and in-situ pumps. They all are needed to fulfil the requirements of the GEOTRACES community and take up to 20 hours per station. The aim of the GEOTRACES group was to measure the concentration and distribution of a variety of trace substances. Dissolved trace metals in seawater were the focus of their research. Iron is a very important trace metal for biological processes in the Antarctic Ocean. It is essential for all living organisms, and thus for the algae also. These algae are the basis of the food-chain of the Antarctic region and are in turn dependent on the availability of iron. However, iron is only found in extremely low concentrations of circa one hundredth of one millionth of a gram per litre seawater (10 nanogram per litre = 10 ng/L = 108 gram per litre). In contrast Polarstern is a strong ship of steel, iron is everywhere on the ship, iron is the ship. Therefore the sampling of seawater is done with the special ultraclean frame holding 24 samplers. Once this frame is back on the deck, it is immediately placed in its own laboratory container, so as to rule out direct contact with the iron of the ship. This allows us to collect the first-ever complete vertical sections, from surface to circa 5 km deep bottom, in the Southern Ocean. Along the Greenwich meridian section we found dissolved iron is very low from 5 ng/L in surface waters increasing to 30 ng/L at great depth. In the southern part of the Weddell gyre, between Maud Rise and the ice shelf of Antarctica, the values are even lower, from 3 ng/L in surface waters to 20 ng/L in deep waters. It is one thing to know how much, or how little, iron there is in the seawater, but in addition we wonder where this iron has come from. Has it been blown into the ocean in dust storms carrying soil dust from land to sea? After all, soil on land contains much natural iron, about 4 percent of soils is iron. Soil also contains much aluminium (Al). Therefore we also measure dissolved Al as a source tracer for dust. Along the Greenwich meridian the concentration of dissolved aluminium in seawater is extremely low, the lowest found thus far in the world oceans. Very low levels of 6 ng/L in surface waters tell us that dust input from land is very small, if any. Therefore the dissolved iron must come from somewhere else. In the sediments the conditions are better for iron to dissolve from the sediment particles and then enter into the bottom waters. So, perhaps that is the source of iron to the sea. We know that another element, manganese (Mn), can also be dissolved in the sediments. Consequently we use manganese as a source tracer for iron coming from below, from the bottom sediments. However the concentrations of dissolved manganese also are extremely low, from 3 ng/L in surface waters to some times about 10 ng/L in deeper layers. Only over the mid-ocean ridge, formed by deep-sea volcanism, we find more manganese, and also more iron, in the deep waters. Hydrothermal circulation associated with deep-sea volcanism, is perhaps the most important source of iron in the ocean waters. Others in the team search for their favourite metal. Zinc and copper are also necessary for all organisms and occur in very low concentrations as well. Overall the dark secrets of the deep unknown waters of the Antarctic Ocean are now being discovered for the first time. Deployment of vertically profiling floats (Argo floats) continued to add to the world wide network with a significant part of the floats being provided by Stephen Riser from the University of Washington. These floats were supposed to drift with the Antarctic Circumpolar Current into the Indian Ocean. Underway we recovered 6 and redeployed 5 PIES. One of the instruments was lost upon recovery. These instruments measured the fluctuations of the Antarctic Circumpolar Current. The mooring work started with the successful recovery of three moorings in the transition zone from the Antarctic Circumpolar Current to the Weddell gyre, which were supposed to measure the exchanges between the two current systems. These moorings could not be redeployed because of funding reasons. The accident On 2 March we reached the Atka Bight in the early hours of Sunday morning, after we had left the operation area on the Greenwich meridian on 28 February. After greyish and partly stormy days we were greeted with Sunday weather in the most literal sense of the word. Everybody was excited, after days of tiring station routine, to enjoy one day on the ice with all the impressions that renders Antarctic research so particularly fascinating. Despite the fact that the scientists had to take into account that they must assist with the loading and pumping work there should still be sufficient time to enjoy the stay on the ice. However when we received at 8:30 am, the news that a helicopter has crashed during the transport of personnel to the Neumayer Station the pleasure of anticipation and expectation altered to shock and grief. The rescue teams from the Neumayer Ill construction site and the Neumayer station quickly arrived at the crash site and had to report the deaths of one of our colleagues from NIOZ, Willem Polman and of the pilot Stefan Winter. The two other passengers Alice Renault and Maarten Klunder were seriously and the helicopter technician Carsten Möllendorf was moderately injured. Inspite of his injuries, the helicopter technician succeeded in removing the other injured persons from the helicopter and radioed for help. We admire his cool head and bravery. The injured persons were transported as quickly as possible with the second helicopter to the hospital on Polarstern where they were cared for. As soon as the news of the terrible event reached AWI, a crisis centre wasestablished at once that was responsible for the organisation and coordination of comprehensive support measures necessary for an immediate return transport of the casualties, the notification of the next of kin and a public statement. Within the shortest period of time an exceptional and unparalleled international cooperation was set up providing the logistical support for the accident victims' instant trip home via Cape Town. On board we gathered together on 3 March for a memorial on the helicopter deck on Monday to bid farewell to our two colleagues. Willem Polman and Stefan Winter lost their lives in the most terrible accident which ever happened in the 25 years of operation of Polarstern. With this ceremony we wanted to express our deepest sympathies to the relatives of the victims and comfort each other and express our highest appreciation of the two deceased to the whole world. The pain, the loss and the fear of the affected families is beyond belief; they are always in our thoughts. A flood of condolences arrived on board, at the AWI and at the NIOZ from all around the world. With this report, we wish to express our thanks for the worldwide sympathy, which provided us with the strength to carry on and get through this difficult situation. As well we want to thank all those who have contributed so that the injured were discovered fast, rescued and taken care of and that our deceased colleagues could begin their last journey with dignity. In addition, we would like to thank all of those who ensured that the injured receive optimal care and could return from Cape Town to their home countries shortly. Only those who were at the location know what it was like for the crews of the station of Neumayer and the construction site and the crew members of Polarstern, pilots, medical personnel, meteorologists, logistical officers, and managers to do all what was needed to limit the extent of this disaster. On 4 March we once again bid farewell with a small group of the most closely affected at the place of the accident. The construction team had built and placed two crosses at the place of the accident. As we held a moment of silence in remembrance, the Basler BT-67 with the bodies on board flew overhead on their flight to Novolazarevskaja, from where the further transport to Cape Town occurred. As a farewell the pilots dipped their wings towards the crosses. It is difficult to imagine a more dignified farewell for a Polar researcher leaving for another world. On 5 March the injured were transported to Cape Town. In the early morning the weather situation seemed to be hopeless. There was continuous snowfall. The injured had to prove further patience. However, we then received the message of the meteorologists: it will improve and the Basler BT-67 has departed from Novolazarevskaja. We admire the courage of the pilots and the skill of the meteorologists because weather really improved. With snow still falling the transport by the PistenBullies from the ship to the airfield began. With pain because of the separation and pleasure of the expectation to know that our friends would soon be in Cape Town and with their relatives we bid farewell to the injured. The pilots took advantage of the short period of better weather, landed, and got the injured on board and started in the last moments before the conditions would not permit the flight anymore. When we were informed about the successful takeoff, we left the shelf ice front and restarted research in Atka Bight. The irony of fate provided us with a sunny afternoon with glorious impressions that are typical for Antarctica during out travel across Atka Bight. It is strange to think that beauty and enchantment could so closely follow horror and grief. However, the decided will to continue our work in the spirit and in remembrance of our deceased colleagues, helped us, to overcome our pain and to return to the routine of research. Our stay at the Station was aimed at supply; we mainly had to supply fuel and food. Additionally, the valuable ice cores, which were drilled at the Kohnen Station, used material and garbage, came on board. Furthermore containers had to be rearranged, to provide space and material, which was used during the next part of the cruise. For this purpose, freight containers had to be moved from the hatch onto the ice, the hatches then had to be opened and lab containers had to be offloaded. Once all these containers were on sledges on the ice, to remove them from the loading area, they were, together with the additional freight containers, then carried back and reloaded in a new sequence. A shunting yard on the shelf ice. Simultaneously, fuel was pumped into the tank containers. The good weather facilitated the work. After the end of the rescue and loading operation we were pleased to accept the invitation of the Station leader to visit the Neumayer Station and to get an impression of the work of the over wintering team. Patiently they explained the properties and function of the station. The farewell of the over wintering team occurred this time only with a short break at the station. The completion of the work on the Greenwich meridian The work on the Greenwich meridian was determined by an alternating sequence of casts with the oceanographic and the ultraclean CTD every 30 nautical miles. Slowly the hydrographic structure of the Weddell gyre appeared in our observations, which we had crossed until the time of leaving to the Neumayer Station up to the foot area of Maud Rise at 65°30'S. A longer phase with relatively weak winds was favourable to this progress. We completed 7 "Super stations" in the context of the GEOTRACESProgramme, 25 ultraclean CTD5 and 73 normal CTD stations to cover all hydrographic regions on the Greenwich meridian with all the relevant parameters. We have recovered 9 moorings and redeployed 5 of them. Two sound sources were recovered and redeployed. The grid of vertically profiling floats was extended by 38 and these drifted under the sea ice of the forthcoming autumns and winters. At the last mooring at about 12 nm north of the edge of the Fimbul Ice Shelf, we encountered a new challenge. When we tried to interrogate the acoustic releases with the POSIDONIA system on board Polarstern no reply was received. So we released blindly and waited for the mooring to show up at the surface. However no float was sighted and no signal was detected with the radio receiver on board from the satellite transmitter, which is mounted on the uppermost part of the mooring. We started to search with the ship and with the helicopter, but with no result. When we were sure that the mooring was not longer at its position, we stopped searching and resumed water sampling stations towards the ice shelf edge. However, shortly after, we were surprised by a message from OPTIMARE in Bremerhaven who are surveying for us the satellite transmitters of the moorings. They informed us that the transmitter had reached the surface shortly after the release signal, though 9 km away from the expected position. We turned immediately towards the indicated position, the helicopter started again and was able to identify the mooring in an ice field in a few miles distance. With this information from the helicopter it was easily possible to approach the mooring with the ship and to recover it quickly. It had damages which clearly indicated that it was removed by an iceberg to a position which was still within the reach of the POSIDONIA transmitter on board to receive the release command, but too far distant for the reply from the less powerful releaser to be received on board. The satellite beacon was pushed by the iceberg so deep into the float assembly that it was hidden for the quasi horizontal view from a distance on the ship, but still visible to the satellite which was on top of it. We were glad about the happy end of the recovery. However, the upward looking sonar was damaged by the iceberg so that the recorded data were lost. Still, it is a great success that all moorings on the Greenwich meridian were recovered after the first 3-year-mooring period, which proves that our mooring technology has reached a standard which allows us to plan such long deployment periods in future. Despite the fact that the data requires comprehensive processing and calibration work, the quality of our instruments is so high, that a first look on the preliminary data from the hydrographic survey indicated that the cooling of the Warm Deep Water which was observed since the mid 9üties has come to a halt. Together with the observation of an earlier warming until the mid 90ties this suggests that decadal fluctuations dominate the variability. Now we can compare the atmospheric forcing during the last years with the one in the early nineties to better understand the forcing mechanism of the fluctuations. The temperature and the salinity of the Weddell Sea Bottom Water increased further during the last three years. This observation provides evidence of the evolution that we have followed since the mid 90s and raised the question even clearer: did global warming reach the deep sea or is it only a fluctuation on a timescale of decades. Because our Australian colleagues report that the salinity of the bottom water in the Ross Sea and off Adelie Land keeps on decreasing, this regional contrast requires an explanation to which we obtained a hint from the data which were obtained in the western Weddell Sea. There the Weddell Sea Bottom Water descends into the deep sea. On 12 March the work on the Greenwich meridian was terminated and we steamed towards the Weddell Sea. In the Weddell Sea The sea ice conditions in the eastern Weddell Sea were determined by a pronounced tongue of sea ice emerging from the South. Since we needed to save time due to the events at the Neumayer Station, we omitted the eastern part of the transect from Kapp Norvegia to Joinville Island. As an alternative it was planned to circumnavigate the ice tongue in the North to gain by easier conditions and omitting station work the required time. However, the forecast of bad weather lead us to the decision to enter the ice. It appeared that the ice was rather easy to break and we proceeded so fast that we decided on 14 March to turn further to the south to be able to begin with the section further to the southeast. However the ice conditions became much more serious and this plan was only partially successful. We had to increase the station distance to 45 nm. The first station on the transect occurred on 15 March at 69°22'S 16°21'W. On 18 March the funeral of Willem Polman took place and on 19 March the obsequies for Stefan Winter. Simultaneously with the ceremonies on land we stopped the work on board and came together for a commemoration. In the solemn company of our ceremonies we were with our thoughts near to the deceased and their families. Even if it was hard for us to overcome our pain, the work on board had to go on. The deep gaps which are left by the deceased and injured colleagues in our hearts and at work have to be bridged as adequately as possible. In this sense a helicopter technician became a winch driver for the ultraclean CTD. With solidarity and even more enhanced efforts we continued the programme in the sense and as an appreciation of the victims. As on the Greenwich meridian, the rhythm of the programme was given by the sequence of lowering and hoisting of the "normal" and ultraclean CTD and the processing of the never ending flow of sampled water. Most of the profiles reached to the sea bottom, but frequently shallow casts (200 to 300 m) were needed to provide large quantities of water for experiments or for extraction of trace substances to be sampled. The moorings which we recovered and deployed were always a particular challenge. In our programme the deployment of sound sources is of particular interest. To obtain measurements in the winter and under the ice, floats were developed which drift at 800 m depths. Once every 10 days they descend first to 2000 m depth and then return to the surface. If there, they are informed of their position and they transfer the measured data by satellites. So far, this is the global Argo system, in the context of which about 3,000 such floats operate in the open ocean and to which we are contributing. However, under the ice this procedure does not work because the floats are not able to reach the surface. For this reason our floats are located by means of the sound sources and the travel times of the signals they transmit. They recognize that they are under the ice because the near surface water temperature is close to the freezing point. Then they stop their ascent and return to depth again. When they reach open water again, they transmit the full recorded data set. In two moorings we have recovered, we encountered a particular phenomenon. The moorings contain buoyancy elements (floats) which are supposed to keep the mooring wire upright in the water column. They consist of glass spheres in plastic housings. In the two last moorings which we recovered we found only remnants of the deepest floats which consisted of the smashed plastic housings which contained sand like glass flour. Those remnants are an impressive demonstration of the impact of the implosion of a glass sphere in about 4,500 m water depth. The discussion on the potential causes is not yet finished. A special challenge is the recovery of moorings under heavy ice conditions. At the last mooring we were due to recover in the Weddell Sea, the great skill built up during decades of experience (25 years Polarstern) and the grain of luck which is always required to be successful, resulted in the recovery at almost 100 % in ice cover. Since the mooring had already been in place for three years and the next opportunity for recovery would be three years later (when the batteries of the releases will be most likely exhausted) there was no alternative but to give it a try. The success fills our hearts with joy and pride. Now we can summarize that after our first deployment period of three years, we were able to recover all moorings. Unfortunately the instruments technology is not as far developed as our mooring technology. Therefore in spite of a 100% recovery rate, we did not achieve a 100% data rate. The evaluation of the data stored in the moored instruments has already begun on board. A first glance showed evidence that the sequence of longer term cooling and warming events detected in the CTD transect repeated in large time intervals were confirmed by the time series from the moored instruments. A particular challenge will now be to find out if there is a relationship between the extreme ice conditions and the water mass properties that together with the atmospheric conditions could result in such changes. To finalize the transect across the Weddell Sea, we needed a lot of patience since the sea ice conditions in the Weddell Sea were extreme. Over the summer two large ice tongues stretched from the southern to the northeastern and the northwestern Weddell Sea. This wider than normal ice extent is consistent with a trend visible in the time series of NSIDC derived from satellite images of increasing sea ice extent in summer during the last decades. However, this does not mean a real increase but only a weaker melting in summer because the winter sea extent remained basically constant. For us, this situation was not only a challenge to be explained but it had direct consequences on the cruise. The onset of ice formation in autumn gave rise to unexpected heavy ice conditions very similar to winter conditions. Heavy ice resulted in lower speed and less station time available, as the original plan was based on mean sea ice conditions. The loss of time had to be compensated through reduction of station times by increasing the station distances. Increasing station distance increases the uncertainty of the estimates of the intensity of variations. In spite of the restrictions, it was possible to probe the relevant water masses sufficiently to detect the correlation of long-term variations in the Weddell Sea and those at the Greenwich meridian. The concentrations of trace substances were measured in an unprecedented manner. In the Weddell Sea we completed 1 "Super station" in the context of the GEOTRACES-Programme, 15 ultraclean CTD5 and 45 normal CTD stations which covered the central and the western part. We have recovered 3 moorings and redeployed 8 of them. Three sound sources were recovered and 4 deployed. Unfortunately we had to take note that two of the recovered sound sources had failed. The grid of vertically profiling floats was extended by 16 and these will now drift under the sea ice of the forthcoming autumns and winters. King George Island and Drake Passage On 30 March we arrived at King George Island after having crossed serious ice conditions north of Joinville Island. The German Dallmann- Labor is run in cooperation at the Argentinean station of Jubany, located at Maxwell Bay on Potter Cove. We were supposed to take freight on board, both here and from the stations Frei and Artigas. A group of seven French and one Chilean scientist were waiting at the Russian station Bellingshausen and two Korean scientists were waiting at the Korean station King Sejong to come on board for the rest of the cruise. They are interested in investigations in Drake Passage. Since the flight from King George Island to Punta Arenas was cancelled, the group who was supposed to return from there had to stay on board until the end of the cruise. After a sunny start in the morning the bay was immersed in fog and we had to wait until flight conditions would prevail for the ship's helicopter to take on board the new scientists and to transfer some equipment as well. On 31 March we left King George Island with a new French/Korean group on board. In addition it was possible to load material from Jubany and Frei stations. However the bad weather conditions, which showed no hope of improvement, forced us to give up our final task of loading material from Artigas. Dense fog prevented any further flights for an unforeseeable future. During the night, we steamed to Drake Passage where an intensive mooring programme took place in addition to the continuation of our measurements of water mass properties and concentration of trace substances. The work was focussed on the French/Korean mooring programme. We intended to recover 10 moorings and redeploy 5 of them. The first two moorings of the Korean group in the southern Drake Passage could be recovered in spite of the unfavourable weather conditions with no problems. Unfortunately there was a problem with the flotation of the following moorings we needed to recover. Most of them had still enough buoyancy to ascend to the surface. However, some of them did so at a rather slow rate. In spite of the fact that they could be monitored by POSIDONIA, this required a lot of patience. Two of the moorings ascended but did not reach the surface. With time consuming operations we tried to dredge them, by paying out about 5000 m of wire which we towed in loops around them. Still, our efforts were not successful. No matter which way we placed our loops (which was not easy with 6 to 7 Bft) the moorings escaped and, disappointed, we had to give up the recovery. In Drake Passage we completed 5 "Super stations" in the context of the GEOTRACES-Programme, 12 ultraclean CTD5 and 46 normal CTD stations. We have recovered 8 moorings and redeployed 5 of them. The grid of vertically profiling floats was extended by 14. The time lost to the problems with the moorings had to be regained by the reduction of the CTD work which resulted in a coarser resolution. Still we were lucky because Drake Passage with famous Cape Hoorn did not show us its most uncomfortable side. Really bad weather only reached us only at the end of the mooring work when we returned to the south to fill in omitted CTD stations. To avoid the bad weather the last CTD station occurred at 56°1.07'S 64°0.59'W on 13 April 2008. When the bad weather arrived we were already steaming towards Le Maire Strait with the wind at our back. On 3 April, we had left Antarctica, when we passed 60°S. On 16 April, the cruise ended according to the plan in Punta Arenas. Scientific background Our cruise was mainly dedicated to the investigation of the oceanic circulation and the biogeochemical processes with their influence on life that depends on them. The main programmes occurred in the context of the International Polar Year 2007/2008 (IPY). The IPY was established under the auspices of ICSU and WMO. It aims to coordinate forces globally to achieve a quasi-synoptic survey of the conditions in both polar areas to obtain a benchmark for future changes. In the GEOTRACES project the role of traces substances in the context of biogeochemical cycles is investigated. The CASO project (Climate of Antarctica and the Southern Ocean) takes up work which had started in the WECCON project (Weddell Sea Convection CONtrol). It aims to investigate processes which occur in the Atlantic Sector of the Southern Ocean and Drake Passage in cooperation with the Bjerknes Centre for Climate Research in Bergen, Norway and the British Antarctic Survey (BAS). In the framework of iAnZone, a programme associated to SCOR (Scientific Committee of Oceanographic Research) and its IPY SASSI project (Synoptic Antarctic Shelf Slope Interactions Study) observation occurred in the area of Maud Rise and the Antarctic Coastal Current. The observations occurred jointly with the IPY GOOD-HOPE project which covers the northern part of the Atlantic sector of the Southern Ocean. The part of the cruise in Drake Passage is part of the French programme DRAKE. The global impact of the regional Processes will be considered in the BIAC (Bipolar Atlantic Thermohaline Circulation) IPY project. The cruise occurs in the context of the MARCOPOLI programme of the Hermann von Helmholtz Association of German Research Centres (HGF). It is a contribution to the Climate Variability and Predictability (CLIVAR) and the Climate and Cryosphere (CIiC) projects of the World Climate Research Programme (WCRP). The ULSs are a contribution to the Antarctic Sea Ice Thickness Project (AnSITP). The deployment of floats occured in the framework of the international Argo programme which contributes to the Global Ocean Observing System (GOOS). As a contribution to the International Polar Year 2007/2008 the cruise was part of the CASO - (Climate of Antarctica and the Southern Ocean) and the GEOTRACES projects. It was the aim to measure ocean currents, temperature, salinity and concentrations of many trace substances in the Southern Ocean. The descending motions in the Southern Ocean are part of the world wide oceanic overturning circulation. They affect the role of the ocean in climate change and biogeochemical cycles. Our measurements raise the question as to whether the deep reaching, descending motion of the overturning, increases again after a phase of slackening. For more than a decade we have observed that the temperatures in the deep Weddell Sea were rising which suggested the reduction of the deep reaching water mass formation in the Antarctic Ocean. Now the temperature is decreasing again. This occurs at a time when sea ice extent in summer is increasing and shows clearly that the potential influence of global warming is not simply to identify from the background of decadal variations. It is of special interest, that the evaluation of satellite data by NSIDC indicated clearly that the Antarctic summer 2007/2008 was the one with the largest ice extent on record. This trend which is particularly strong in the Atlantic sector of the Southern Ocean is in clear contrast to the Arctic where a strong decrease of the summer ice extend is observed. To understand the opposing trends in the Antarctic and the Arctic is an obvious aim of our cruise. Because those changes occur over decades and are subject to significant spatial variations ships cruises like the one of Polarstern are not enough to track them with sufficient accuracy. Therefore we need comprehensive autonomous observing systems which can be moored or feely drifting. They are a component of the Southern Ocean Observing System (SOOS) which is under development these days. As a contribution to such a system we deployed, in international cooperation, 18 moored systems and recovered 20 of them. With the recording period of three years we have reached a record length. We deployed 67 floats, the ones which were deployed in the Weddell Sea are able to operate under the ice. They have an operation period of up to five years and form a network of unprecedented coverage of this part of the earth. During the International Polar Year 2007/2008 we expected not only to provide new knowledge on the role of the polar areas in the earth system, but in addition, it was an aim of high priority to include the public and, in particular, the younger generation in actual research and instruct them comprehensively. For this purpose, we had two teachers on board. They participated actively in the research work and transmitted their experiences on a regular basis to their students, colleagues and newspapers by telephone, email and internet. Their experiences will reach other schools via an IPY teacher's network and hopefully school books too. 2. CASO - (CLIMATE OF ANTARCTICA AND THE SOUTHERN OCEAN) The CASO project (Climate of Antarctica and the Southern Ocean) takes up work which had started in the WECCON project (Weddell Sea Convection CONtrol). It aims to investigate processes which occur in the Atlantic Sector of the Southern Ocean and Drake Passage in cooperation with the Bjerknes Centre for Climate Research in Bergen, Norway and the British Antarctic Survey (BAS). In the framework of iAnZone, a programme associated to SCOR (Scientific Committee of Oceanographic Research) and its IPY SASS I project (Synoptic Antarctic Shelf Slope Interactions Study) observation occur in the area of Maud Rise and the Antarctic Coastal Current. The observations occur jointly with the IPY GOOD-HOPE project which covers the northern part of the Atlantic sector of the Southern Ocean. The global impact of the regional Processes will be considered in the BIAC (Bipolar Atlantic Thermohaline Circulation) IPY project. The cruise occurs in the context of the MARCOPOLI programme of the Hermann von Helmholtz Association of German Research Centres (HGF). It is a contribution to the Climate Variability and Predictability (CLI VAR) and the Climate and Cryosphere (CIiC) projects of the World Climate Research Programme (WCRP). The ULS are a contribution to the Antarctic Sea Ice Thickness Project (AnSITP). The deployment of floats occurs in the framework of the international Argo programme which contributes to the Global Ocean Observing System (GOOS). 2.1 DECADAL VARIATIONS OF WATER MASS PROPERTIES IN THE ATLANTIC SECTOR Olaf Boebel(1), Carmen Boening(1), Luisa (1)Alfred -Wegener-Institut Christini(1), Eberhard Fahrbach(1), (2)CNRS-LEGOS Veronique Garcon(1), Olaf Klatt(1), (3)OPTIMARE Marielle Lacombe (2), Matthias (4)LOCEAN Monsees(3), Ismael Nunez-Riboni(1), Christine Provost(4), Alice Renault(4), Gerd Rohardt(1), Hendrik Sander (3), Nathalie Sennechael(4), CTD watch since Jubany, Aurelie Spadone(4), Olaf Strothmann(1), Joel Sudre(2), Stephan Theisen(1) Objectives The densest bottom waters of the global oceans originate in the Southern Ocean. Production and export of these dense waters constitute a vital component of the global climate system. The formation of dense water in polar areas is controlled to a large extend by the delicate balance between supply of fresh water through precipitation and melt of continental and sea ice and the extraction of freshwater by sea ice formation and evaporation. Therefore the Southern Ocean's part of the global freshwater cycle links continental and oceanic conditions. It consists in the transport of freshwater from the continent through melting of ice shelf and icebergs and is strongly mediated by redistribution of freshwater through the highly variable and moving sea ice cover on which snow is accumulated as well as by the oceanic circulation. Coupled models predict an intensification of the freshwater cycle in the context of global warming. Observations of the freshening of Subantarctic Mode, intermediate and deep waters suggest that the intensification is ongoing. Therefore the better understanding of the Southern Ocean freshwater balance is urgently needed. It can only be achieved by a quasi-simultaneous comprehensive circumpolar assessment by multi-platform observations and modelling. The influence of Southern Ocean waters can be traced far into the northern hemisphere. As deep and bottom waters, they represent the deepest layer of the global overturning circulation. The conditions in the Southern Ocean are largely controlled by the Antarctic Circumpolar Current (ACC), the worlds most powerful current system, which transports about 140 Sv (106 m3 1) of water at all depths. It connects the three ocean basins and forms an isolating water ring around the Antarctic continent. South of the ACC, in the subpolar region, warm and salty water masses are carried in the subpolar gyres to the continental margins of Antarctica. The most prominent are the Weddell and Ross gyres. In the subpolar gyres, water mass modifications occur through ocean-ice-atmosphere interactions and mixing with adjacent water masses. The ACC is dynamically linked to meridional circulation cells, formed by southward ascending flow in intermediate depth feeding into northward flow above and below. In the deep cell water sinking near the continental water spreads to the adjacent ocean basins, in the shallow cell the northward flow occurs in the near surface layers. Dense waters are produced at several sites near the continental margins of Antarctica. Quantitatively the most important region for dense water formation may well be the Weddell Sea, however other areas provide significant contributions as well. The basic mechanism of dense water generation involves upwelling of Circumpolar Deep Water which is relatively warm and salty into the surface layer where it comes into contact with the atmosphere and sea ice. The newly formed bottom water is significantly colder and slightly fresher than the initial Circumpolar Deep Water which indicates heat loss and the addition of freshwater. Since freshwater input in the upper oceanic layers is prohibitive to sinking through increasing stability of the water column, it has to be compensated by salt gain through fresh water extraction. The upwelled water is freshened by precipitation and melting of glacial and sea ice. Freshwater of glacial origin is supplied from the ice shelves or melting icebergs. Ice shelves melt at their fronts and undersides related to the oceanic circulation in the cavity. Iceberg melting depends highly on the iceberg drift and can supply freshwater to areas distant from the shelves as the Antarctic frontal system. Due to the spatial separation of major freezing and melting areas of sea ice cooling and salt release during sea-ice formation cause the compensation of the freshwater gain and subsequently the density increase which is needed for bottom water formation. Significant parts of the salt accumulation occur on the Antarctic shelves in coastal polynyas. Since extreme heat losses can only occur in ice free water areas, the polynyas are areas of intense sea ice formation. Offshore winds compress the newly formed sea ice and keep an open sea surface in the polynyas. The cold and saline water accumulated on the shelves can descend the continental slope and mix with water masses near the shelf edge or it circulates under the vast ice shelves, where it is further cooled below the surface freezing point and freshened by melting of the ice shelf. The resulting Ice Shelf Water spills over the continental slope and mixes with ambient waters to form deep and bottom water. For both mechanisms relatively small scale processes at the shelf front, topographic features and the nonlinearity of the equation of state of sea water at low temperatures is of special importance to induce and maintain the sinking motion. The different processes, topographic settings and atmospheric forcing conditions lead to variable spatial characteristics of the resulting deep and bottom water masses which than spread along a variety of pathways to feed into the global oceanic circulation. Climate models suggest that dense water formation is sensitive to climate change. However, since the relatively small scale formation processes are poorly represented in the models further improvement is needed. The overturning affects as well the biogeochemical cycles and consequently its change can have a significant impact on ocean carbon uptake. The properties and volume of the newly formed bottom water underlies significant variability on a wide range of time scales, which are only poorly explored due to the large efforts needed to obtain measurements in ice covered ocean areas. As for the atmospheric driving forces, the sea ice and upper ocean layers, seasonal variations are partly known and normally exceed in intensity the other scales of variability. However the spatial distribution pattern of the variability is only poorly resolved e.g. seasonal cycles of sea ice thickness are only available at a few sites. An estimate of the sea ice mass as a baseline to detect change is still not possible due to the missing measurements of sea ice thickness. Longer term variations of the atmosphere-ice- ocean system as the Antarctic Circumpolar Wave, the Southern Hemispheric Annular Mode and the Antarctic Dipole are only poorly observed and understood. Their influence on or interaction with oceanic conditions are only guessed on the basis of models which are only superficially validated due to lack of appropriate measurements. The extreme regional and temporal variability represents a large source of uncertainty when data sets of different origin are combined. Therefore circumpolar data sets are needed of sufficient spatial and temporal coverage. At present such data sets can only be acquired satellite remote sensing. However, to penetrate into the ocean interior and to validate the remotely sensed data, an ocean observing system is needed, which combines remotely sensed data of sea ice and surface properties with in-situ measurements of atmospheric, sea ice and oceanic properties. To achieve further progress significant steps occurred in the development of appropriate technology and logistics. Oceanic properties are measured under the sea ice which required the development of under- ice acoustic ranging and data transmitting systems. To construct from the achievable observations a comprehensive circumpolar view, model assimilations have to be done which require the development of appropriate models. During the International Polar Year 2007/2008 a set of meridional transects was occupied in one season to provide the first synoptic snapshot of the circulation, stratification and biogeochemical status of the Southern Ocean. It included each of the "chokepoint" sections between Antarctic and the southern hemisphere continents. ANT-XXIV/3 covered the African chokepoint in the Atlantic Sector of the Southern Ocean, the Weddell Sea and Drake Passage. The northern part of the section south of Africa was taken care by BONUS-GOODHOPE. Work at sea The Polarstern cruise ANT-XXIV/3 complemented the efforts during the International Polar Year 2007/2008 to obtain in-situ observations in the Atlantic sector of the Southern Ocean in order to allow a circumpolar view. Time series stations with moored instruments provided measurements in the deep and the surface layers and of ice thickness. For this purpose moorings with current meters, temperature and salinity sensors as well as upward looking sonars were recovered and redeployed. The cruise concentrated to three major areas: the Greenwich meridian, the Weddell Sea and Drake Passage. Measurements occurred along the Greenwich meridian, across the Weddell Sea and Drake Passage (Fig. 21). The ship borne surveys in summer are imbedded in the time series measurements with moorings, drifters and floats to derive the effect of the seasonal variability on transfer processes and to avoid the aliasing effect on longer term observations. Moorings were recovered (Fig. 2.lb) and redeployed (Fig. 2.lc). The details of the moored instruments are summarized in Tab. 25 to 2.6. The spreading of floats is able to extend the data from the sections over larger parts of the area. Ship borne meridional transects were obtained to determine water mass properties including tracer concentrations (Fig. 2.1.d). Fig. 2.1: The cruise track of ANT-XXIV/3 (a) and the locations of moorings recovered (b) deployed (c) and the CTD stations (d) Profiling floats were deployed. The float system has to complement Argo in ice-fee and under-ice condition to reach a global coverage. Moorings with sound sources for under ice navigation were recovered and redeployed. The IPY set the goal of achieving at least the 3° X 3° sampling of the global array throughout the southern hemisphere oceans south of 30°S, for the full duration of the IPY (March 2007 to March 2009). Acoustically tracked floats will provide profiles and current velocities from key ice-covered seas. The floats are programmed to continue to profile and store data beneath ice. Once the floats detect open water, the stored profiles are transmitted. While the position of the sub-ice profiles is not known without acoustic navigation, the floats can survive the winter and the stored profiles provide a statistical description of winter stratification. Preliminary results Despite the fact that the data requires comprehensive processing and calibration work, the quality of our instruments is so high, that a first look on the preliminary data from the hydrographic survey indicated that the cooling of the Warm Deep Water which was observed since the mid 90ties has come to a halt. Together with the observation of an earlier warming until the mid 90ties this suggests that decadal fluctuations dominate the variability. Now we can compare the atmospheric forcing during the last years with the one in the early nineties to better understand the forcing mechanism of the fluctuations. The temperature and the salinity of the Weddell Sea Bottom Water increased further during the last three years at the Greenwich meridian. This observation provides evidence of the evolution that we have followed since the mid 90s and raised the question even clearer: did global warming reach the deep sea or is it only a fluctuation on a timescale of decades. Because our Australian colleagues report that the salinity of the bottom water in the Ross Sea and off Adelie Land keeps on decreasing, this regional contrast requires an explanation to which we obtained a hint from the data which were obtained in the western Weddell Sea where the data from the moored instruments showed cooling of the Weddell Sea Bottom Water. The descending motions in the Southern Ocean are part of the world wide oceanic overturning circulation. They affect the role of the ocean in climate change and biogeochemical cycles. Our measurements raise the question as to whether the deep reaching, descending motion of the overturning, increases again after a phase of slackening. For more than a decade we have observed that the temperatures in the deep Weddell Sea were rising which suggested the reduction of the deep reaching water mass formation in the Antarctic Ocean. Now the temperature near the formation area in the western Weddell Sea is decreasing again. This occurs at a time when sea ice extent in summer is increasing and shows clearly that the potential influence of global warming is not simply to identify from the background of decadal variations. 2.1.1 CTD transects Hydrographic surveys were carried out along the Greenwich meridian, from Kapp Norvegia to the northern end of the Antarctic Peninsula and across Drake Passage with a CTD (Conductivity/Temperature/Depth) probe and a rosette water sampler (Fig. 2.ld). Samples were taken to measure the components of the CO2 system, oxygen, nutrients, and tracers. A total number of 217 CTD stations were carried out during the cruise. Two independent systems were used. The standard CTD/water sampler (here indicated as "AWI CTD") consists of a SBE91 1 plus CTD system in combination with a carousel water sampler SBE32 with 24 12-l bottles. Bottle number 1 and 2 were not used because of up- and down looking ADCPs which have been installed at the carousel frame. To determine the distance to the bottom we used an altimeter from Benthos. In addition to this a transmissiometer from Wetlabs, a SBE43 oxygen sensor from Seabird Electronics and a Dr. Haardt Fluorometer has been used. The second system was the ultraclean water sampler (here indicated as "NIOZ CTD") from the GEOTRACES group (See 3.1.9). This water sampler was also equipped with a SBE91 1 plus CTD. In addition the following external sensors were installed at the NIOZ CTD: I) a SBE43 oxygen sensor from Seabird, II) a Seapoint OBS, and Ill) a Chelsea Aquatracka fluorometer. A high precision thermometer SBE35 was used to check the CTD temperature sensors. A mechanical bottom switch with 10 m rope length was used. The altimeter did not work reliably. Both CTD systems were equipped with two independent CT sensor pairs. Each senor pair has its own pump to flush the cell at a constant flow of water. The oxygen sensor was integrated in the first pair. The serial numbers, the type of each sensor and the calibration dates of each device can be taken from Tab. 21 and 2.2. Tab. 2.1a: Configuration of the AWI CTD CTD SBE9llpIus SN 0287 with rosette SBE 32 Pressure (Type/SN, Cal.-date) Digiquartz 4 19K-105/SN 51197, 20.11.1992 Sensors in pair: Pair 1 Pair 2 --------------------------------- ---------------------- ---------------------- Temperature (Type/SN, Cal.-Date) SBE 03P/2929, 10.04.07 SBE 03P/1373, 10.05.07 Conductivity (Type/SN, Cal.-Date) SBE 04C/3173, 26.04.07 SBE 04C/2470, 10.04.07 Tab. 2.2a: Additional sensors of the AWI CTD Sensor Type Cal.-date Analog channel (Voltage) ---------------- ----------------------------- --------- ------------- Altimeter Benthos PSA 916D SN 208 - 6 Transmissiometer WET labs C-Star SN CST-814DR 23.07.99 0 Fluorometer Dr Haardt Mod. 1101.3 SN 8060 - 2 Oxygen (Type/SN) SBE43 SN 0743 28.02.06 4 Tab. 2.1b: Configuration of the NIOZ CTD CTD SBE91 1 plus SN 0230 with Ultraclean Water Sampler Pressure (Type/SN, Cal.-date) Digiquartz 419K-105/SN 43517, 28.02.2006 Sensors in pair. Pair 1 Pair 2 --------------------------------- ---------------------- ---------------------- Temperature (Type/SN, Cal-Date) SBE 03P/2118, 09.11.07 SBE 03P/1360, 28.11.07 Conductivity (Type/SN, Cal-Date) SBE 04C/3035, 09.11.07* SBE 04C/3385, 09.01.08 SBE 04C/0776, 29.11.07** *: used from station 97 cast 2 until station 135 cast 1 **: used from station 138 cast 1 until station 252 cast 1 Tab 2.2b: Additional sensors of the NIOZ CTD Sensor Type Cal.-date Analog channel (Voltage) ---------------- ----------------------------- --------- ------------- Altimeter unknown - - Transmissiometer Seapoint OBS SN 1066 - - Fluorometer Chelsea Aquatracka MKIII SN 092 - - Oxygen (Type/SN) SBE43 SN 0654 22.11.07 - The salinity is given in Practical Salinity Units (PSU). Salinity samples were analysed with an Autosal salinometer 8400B from Guildline Instruments to check and probably correct the conductivity measurements of the CTD. Therefore once per day double samples were taken from 6 depth levels which show no significant gradient in the salinity differences. The salinity measurements were directly compared with the CTD measurements. The water samples were measured in reference to Standard water batch no P149 (K1 5=0.99984) from 10. May 2007. AWI CTD The difference between conductivity from sensor pair 1 and 2 showed an increasing drift of the primary conductivity sensor from the first to the last profile. This was confirmed by the post-calibration of the sensors carried out after the cruise. Therefore the secondary sensor pair was taken for the final data set. 21 deep casts were made with both, the AWI- and the NIOZ CTD. These profiles were used to compare all temperature sensors against each other resulting in a temperature correction of -0.00065°C for the secondary temperature sensor. The pre- and post-calibration of the secondary conductivity sensor shows no drift but the evaluation of the Autosal measurements indicated a pressure dependent correction, which is in the order less than the sensor specification (see Fig. 2.2). Fig. 2.2: Salinity differences of AWI CTD plotted versus pressure. The uncorrected salinity is in the range of the sensor specification, see Fig. 2.3 below. The applied correction based on the Autosal measurements and the pre- and post-calibration from the manufacturer. Scorr = SCTD + AS with AS = a + b * P P:= Pressure (dbar) a := 3.8 * iO b:= -8.6667 * 1O' Fig. 2.3: Salinity differences of AWI CTD before and after correction from Autosal measurements taken from deep samples (greater 2,000 m) only. The shaded region indicates the range of the sensor specification. NIOZ CTD The secondary sensor pair was influenced by a strong noisy signal. The reason is still unclear. The same feature was already observed during the Polarstern cruise ARK-XXII/3. Therefore the primary sensor pair was taken for the final data set in spite of a sensor exchange due to a broken conductivity cell which happened at station 135, cast 1. No correction must be applied for the secondary temperature, which results from comparison between the secondary and primary sensors. This result was confirmed by the pre- and post-calibration and the comparison between AWIand NIOZ CTD (see 21 deep casts). No correction must be applied for the conductivity carried out with SN 3035; see Fig. 24. Data measured with the spare sensor SN 0776 need to be corrected with a constant offset of -O001 37.These correction could be confirmed with the help of the pre- and post-calibration results. Fig. 2.4: Salinity differences of NIOZ CTD before and after correction from Autosal measurements taken from deep samples (greater 2,000 m) only. The shaded region indicates the range of the sensor specification. After each single correction step temperature and salinity were checked using the T/S relation including all available profiles from AWI and NIOZ CTD and in addition data from previous cruises were taken into account. This method was used to correct the different performance of the two systems which was finally controlled by contour plots (Fig. 25). Fig. 2.5: Example of the density contour plot from the layer 2,000 to 2,500 m along the Greenwich meridian, which demonstrates the influence by the use of two independent CTD systems before and after the final processing. A) is the uncorrected and B) the corrected density contour plot. The arrows in the upper panel showed the location of the neighbouring CTD casts carried out with the AWI and NIOZ CTD. The data quality for salinity is better than ± 0.002 and for temperature better than :t 0.001 K. The temperature and salinity data are presented as vertical sections in Fig. 2.6 to 28. Fig. 2.6: Vertical transect of potential temperature (top panel) and salinity (bottom panel) along the Greenwich meridian Fig. 2.7: Vertical transect of potential temperature (top panel) and salinity (bottom panel) across the Weddell Sea from Kapp Norvegia (right) to Joinville Island (left) Fig. 2.8: Vertical transect of potential temperature (top panel) and salinity (bottom panel) across the Drake Passage from South America (left) to the Antarctic continent (right) 2.1.2 Underway measurements Underway measurements with a vessel mounted 150 kHz-Ocean Surveyor ADCP from RD Instruments and two SBE21 thermosalinographs from Seabird Electronics were conducted along the whole track to supply temperature, salinity and current data at a high spatial resolution (Figs. 29, 210, and 2.11). The intakes of the thermosalinographs are mounted in 5 m depth in the bow thruster tunnel (TSB) and in 11 m depth in the keel (TSK). Both instruments were controlled by taking water samples each day which were measured on board with the Autosal 8400B. The final corrected and verified thermosalinograph data can be retrieved from the AWI database using: http://www.awi.de/de/infrastruktur/schiffe/polarstern/bordwetterwarte/continuous_measurements/ Fig. 2.9: Near surface temperature and salinity from the thermosalinograph (keel) along the trackline from South Africa (left) to the Antarctic continent (right) Fig. 2.10: Near surface temperature and salinity from the thermosalinograph (keel) across the Weddell Sea from Joinville Island (right) to Kapp Norvegia (left) Fig. 2.11: Near surface temperature and salinity from the thermosalinograph (keel) across Drake Passage from South America (left) to the Antarctic continent (right) 2.1.3 LADCP (Lowered acoustic Doppler profiler) Objectives Full depth profiles of horizontal ocean currents were measured with two lowered acoustic Doppler profilers (LADCP) attached to the AWI OlD Rosette. CTD/LADCP stations were performed along the three transects (the Greenwich meridian, the Weddell Sea and the Drake Passage, Fig. 21), in order to complement the mooring arrays. The LADCP data along these transects in the Atlantic sector of the Southern Ocean will contribute to a better understanding of the Southern Ocean in the Atlantic sector including the Weddell Sea. The Antarctic Circumpolar Current (ACC), is a key element of the global climate system. The LADCPs data will provide a picture of the ACC transport across Drake Passage within a period of approximately 12 days. With a high resolution CTD/LADCP station section, the LADCP data will help to document the current structure. Work at sea The measurements were done with two RDI Workhorse 300 kHz ADCP5. An external battery case was used to supply power to the two LADCPs. Between two consecutive stations, the data from the two LADCP5 were downloaded from their internal memory card and the power supply was checked. A Master/Slave configuration was used in which the Master ADCP was downward looking and the Slave ADCP was upward looking. Unfortunately the signal could not be synchronised between the two LADCPs and a unique configuration was used for each LADCP. The LADCP measurements are summarized in Tab. 2.3 and 2.4. On the Greenwich meridian section we did a total of 24 profiles with the LADCPs. For 13 of them both upward and downward looking LADCP5 worked, and for the others only the downward -looking LADCP could get data. On the Weddell Sea section we did a total of 52 profiles. On six of them, only the downward-looking LADCP was working properly and could acquire data. Tab. 2.3: LADCP measurements during ANT-XXIV/3 Transect Greenwich Weddell Drake meridian Sea Passage ------------------------------------ --------- ------- ------- Number of CTD/LADCP stations 24 52 31 Downward looking profile alone 11 6 12 Upward and downward looking profiles 13 46 31 Expected results Processing was not completed on board. The quality of the data has to be tested in order to validate the raw data. The second step consists in the computation of the currents over the whole water column. The data coming from vessel mounted ADCP (VADCP) will be used to better constraint the first 300 meters. The profiles through the whole Drake Passage will allow the computation of the ACC transport across the section. Tab. 2.4: Location of the LADCP profiles Station Date Lat Lon Depth LADCP [m] Down Up ---------- -------- ---------- ---------- ------ ---- -- PS711099-2 13.02.08 41° 8.71'S 9°58.28'E 4761.0 1 1 PS71I101-3 13.02.08 42°21.36'S 8°59.93'E 4640.0 1 1 PS71/102-2 15.02.08 44°39.56'S 7° 5.77'E 4606.0 1 0 PS71/104-6 17.02.08 47°39.05'S 4°16.20'E 4544.2 1 0 PS71/106-1 18.02.08 48°54.71'S 2°47.88'E 4094.3 1 0 PS71/108-2 19.02.08 51°29.95'S 0° 0.02'W 2775.4 1 0 PS71/112-1 20.02.08 52°30.20'S 1°22.26'W 2811.4 1 0 PS71/113-3 20.02.08 52°59.75'S 0° 2.30'E 2522.4 1 0 PS71/115-2 21.02.08 53°30.95'S 0° 0.30'E 2657.7 1 0 PS71/118-2 21.02.08 54°30.19'S 0° 1.76'E 1718.8 1 0 P571/121-1 22.02.08 55°29.76'S 0° 0.34'W 3837.3 1 0 P571/124-1 22.02.08 56°30.34'S 0° 1.22'E 4055.3 1 1 P571/125-1 23.02.08 57° 0.11'S 0° 0.17'W 3837.3 1 1 PS71/127-1 23.02.08 57°29.91'S 0° 1.20'E 4056.7 1 1 P571/130-1 24.02.08 58°29.96'S 0° 0.03'W 4184.8 1 0 P571/131-1 24.02.08 59° 0.06'S 0° 0.17'E 4584.2 1 1 P571/134-1 25.02.08 59°30.98'S 0° 1.77'E 4710.8 1 1 P571/137-1 26.02.08 60°29.99'S 0° 0.04'E 5355.5 1 1 P571/140-1 27.02.08 61°29.91'S 0° 0.35'W 5378.0 1 1 PS71/141-2 27.02.08 61°59.98'S 0° 0.04'E 5359.2 1 1 P571/143-1 27.02.08 62°30.58'S 0° 0.56'W 5337.7 1 1 P571/146-1 28.02.08 63°30.01'S 0° 0.03'W 5236.3 1 0 P571/149-1 29.02.08 64°29.99'S 0° 0.04'E 4660.9 1 1 P571/152-1 29.02.08 65°30.04'S 0° 0.34'E 3972.6 1 1 PS71/157-5 08.03.08 66°28.60'S 0° 1.85'W 4493.2 1 0 P571/158-1 08.03.08 66°14.73'S 0° 1.07'W 3683.5 1 1 PS71/159-4 08.03.08 66° 1.41'S 0° 7.93'E 3547.5 1 0 PS71/161-4 09.03.08 66°29.93'S 0° 0.20'E 4536.5 1 0 P571/165-1 10.03.08 67°30.01'S 0° 0.08'E 4625.5 1 0 P571/169-1 10.03.08 68°30.02'S 0° 0.12'E 4256.2 1 1 P571/171-1 10.03.08 68°45.02'S 0° 0.00'W 3627.7 1 0 P571/173-1 10.03.08 69°11.89'S 0° 1.61'E 2905.2 1 0 P571/174-1 11.03.08 69° 5.96'S 0° 0.24'W 3223.5 1 0 P571/175-1 11.03.08 69° 0.72'S 0° 0.05'E 3374.5 1 0 P571/177-1 11.03.08 69°18.08'S 0° 0.31'W 2457.2 1 1 P571/178-1 11.03.08 69°24.07'S 0° 0.18'W 2000.5 1 1 P571/179-1 12.03.08 69°30.98'S 0° 3.14'W 1519.2 1 1 P571/181-1 12.03.08 69°36.58'S 0° 0.34'W 1506.2 1 1 P571/183-1 12.03.08 69°36.55'S 0°40.05'W 2264.5 1 1 Station Date Lat Lon Depth LADCP [m] Down Up ---------- -------- ---------- ---------- ------ ---- -- PS71/184-1 13.03.08 69° 0.00'S 6°58.33'W 2942.5 1 1 PS71/185-1 15.03.08 69°21.69'S 16°25.87'W 4737.5 1 1 PS71/186-1 15.03.08 69° 3.86'S 17°21.38'W 4766.5 1 1 PS71/188-1 16.03.08 68°23.60'S 19° 4.19'W 4826.7 1 1 PS71/189-1 16.03.08 67°56.57'S 20° 0.04'W 4905.0 1 1 PS71/190-1 17.03.08 67°35.95'S 21°47.96'W 4905.2 1 1 PS71/192-1 17.03.08 66°56.84'S 25°17.27'W 4852.0 1 1 PS71/193-1 18.03.08 66°37.26'S 27° 4.85'W 4865.0 1 1 PS711194-1 19.03.08 66°24.72'S 29° 1.09'W 4827.7 1 1 PS71/195-1 20.03.08 66°13.02'S 30°55.42'W 4810.2 1 1 PS71/196-1 20.03.08 66° 0.50'S 32°46.46'W 4789.7 1 1 PS71/197-1 20.03.08 65°48.54'S 34°37.55'W 4787.0 1 1 PS71/198-1 21.03.08 65°36.82'S 36°23.82'W 4771.2 1 1 P571/199-1 21.03.08 65°27.20'S 37°42.46'W 4730.5 1 1 P571/200-1 22.03.08 65°16.95'S 39° 1.32'W 4766.2 1 1 P571/201-1 22.03.08 65° 7.01'S 40°19.31'W 4774.5 1 1 P571/202-1 22.03.08 64°56.89'S 41°39.90'W 4733.2 1 1 P571/205-1 23.03.08 64°33.97'S 44°13.71'W 4592.7 1 1 P571/206-1 24.03.08 64°28.19'S 45°11.21'W 4484.5 1 1 PS71/207-3 24.03.08 64°23.03'S 45°55.50'W 4442.5 1 1 P571/208-1 24.03.08 64°17.84'S 46°38.62'W 4392.2 1 1 P571/209-1 25.03.08 64°11.42'S 47°31.81'W 4200.2 1 1 P571/211-1 26.03.08 63°54.58'S 48°39.48'W 3725.0 1 1 P571/212-1 26.03.08 63°54.37'S 49° 4.69'W 3520.2 1 1 P571/213-1 26.03.08 63°53.45'S 49°35.38'W 3304.2 1 1 P571/214-1 27.03.08 63°51.31'S 50° 0.28'W 2938.0 1 1 P571/215-1 27.03.08 63°46.68'S 50°25.67'W 2660.2 1 1 P571/216-5 28.03.08 63°41.47'S 50°50.39'W 2536.7 1 1 P571/217-1 28.03.08 63°42.09'S 51°18.52'W 2255.5 1 1 P571/218-1 28.03.08 63°36.85'S 51°40.05'W 1786.5 1 1 P571/219-1 28.03.08 63°32.70'S 51°53.33'W 1230.0 1 1 PS71/220-2 28.03.08 63°28.17'S 52° 6.35'W 939.5 1 0 P571/221-1 28.03.08 63°24.11'S 52°32.23'W 514.5 1 0 P571/222-1 29.03.08 63°21.19'S 52°51.24'W 444.5 1 1 PS71/223-1 29.03.08 63°17.20'S 53°13.97'W 431.0 1 1 P571/224-1 31.03.08 62°12.28'S 58°56.04'W 90.5 1 1 P571/225-1 01.04.08 60°42.41'S 53°36.97'W 1496.2 1 0 PS71/226-3 02.04.08 60°37.63'S 53°49.88'W 2777.2 1 1 P571/227-1 02.04.08 60°32.15'S 54° 5.65'W 2971.0 1 1 P571/228-1 02.04.08 60°26.44'S 54°19.42'W 3185.0 1 1 P571/229-1 02.04.08 60°16.28'S 54°47.76'W 3265.2 1 1 Station Date Lat Lon Depth LADCP [m] Down Up ---------- -------- ---------- ---------- ------ ---- -- PS71/231-2 03.04.08 59°55.50's 55°44.52'W 3577.5 1 1 PS71/232-1 03.04.08 59°45.59'S 56°14.98'W 3629.2 1 1 PS71/233-2 04.04.08 59°33.51'S 56°40.24'W 3578.2 1 0 PS71/234-1 05.04.08 59°21.48'S 57° 8.42'W 3556.5 1 1 PS71/235-1 05.04.08 59° 9.49'S 57°37.99'W 3651.2 1 1 PS711236-6 06.04.08 58°59.99'S 58° 8.69'W 3790.2 1 0 PS711237-1 06.04.08 58°39.12'S 58°47.30'W 3928.5 1 0 PS711238-3 06.04.08 58°17.02'S 59°28.18'W 3543.0 1 0 PS711239-1 07.04.08 58° 5.85'S 60' 0.16'W 4082.7 1 1 PS71/240-1 07.04.08 57°52.39'S 60°27.14'W 3898.2 1 1 PS71/241-1 07.04.08 57°38.36'S 60°53.81'W 3500.7 1 0 PS71/242-1 08.04.08 57°30.13'S 61° 6.39'W 3911.2 1 0 PS71/243-1 08.04.08 57°23.94'S 61°24.32'W 3731.0 1 0 PS71/244-6 09.04.08 56°51.50'S 62°30.20'W 4146.2 1 1 PS71/246-1 10.04.08 57° 6.96'S 61°58.54'W 3774.0 1 1 PS71/247-1 10.04.08 56°39.70'S 62°48.94'W 4065.0 1 1 PS71/248-1 10.04.08 56°25.00'S 63°18.63'W 3982.5 1 1 PS71/250-8 12.04.08 55°43.96'S 64°25.68'W 3822.2 1 1 PS71/251-1 12.04.08 55°20.63'S 65° 9.19'W 1762.7 1 1 PS71/252-2 12.04.08 55° 7.49'S 65°29.44'W 468.2 1 1 PS71/253-1 12.04.08 55°13.66'S 65°20.74'W 1061.2 1 1 PS71/254-1 13.04.08 55°27.98'S 64°56.91'W 2563.2 1 0 P571/255-1 13.04.08 55°35.35'S 64°44.01'W 3619.0 1 0 P571/256-1 13.04.08 55°53.30'S 64°15.31'W 3878.0 1 0 P571/258-1 13.04.08 56° 0.24'S 64° 0.56'W 3987.7 1 0 TOTAL 106 73 ZERO 39 20 Weddell 36 34 DRAKE 31 19 106 73 2.1.4 Moorings Work at sea In order to detect variations with sufficient time resolution to avoid the effect of aliasing and to be able to separate processes of a wide range of time scales quasicontinuous measurements from moored instruments are needed. Recovery and deployment of moorings Since the previous cruise ANT-XXII/3 moorings were maintained along two sections. The first are a set of 9 moorings on the Greenwich meridian. The other section crosses the Weddell Sea from Kapp Norvegia towards Joinville Island at the tip of the Antarctic Peninsula. Greenwich meridian moorings The moored observing system on the Greenwich meridian is maintained since 1996. Current meter moorings were exchanged in 1998, 1999, 2001, 2003 and 2005. But three moorings AW1229, AW1231 and AW1232 were already exchanged 2006 because of the high sample rate of the ADCP5 in these moorings. Some mooring positions were modified and additional ones were added during this period. During the present leg the moorings deployed in 2005 (Figs. 21b, 212 and Tab. 2.5) were recovered and a new reduced set was deployed (Figs. 2.1 c, 2.14 and Tab. 2.6). The two southernmost moorings covered the area of the coastal and slope current. West of Maud Rise there are three moorings equipped with temperature- conductivity recorders from approximately 250 to 750 meters depth to monitor the stratification in the transition from the Winter Water to the Warm Deep Water. These data should indicate the potential pre-conditioning for the occurrence of a polynya. Three of the northernmost moorings were not redeployed and the remaining northern mooring was continued with a near bottom CT recorder only. The southernmost mooring was not redeployed neither. The observations along the Greenwich meridian are concentrated on Maud Rise and the continuation of the sea ice thickness measurements with the Upward Looking Sonars (ULS) in combination with the ADCP. Two sound sources were exchanged in moorings AW1229 and AW1231 to locate floats. Further details are given in 2.1.5. Weddell Sea moorings The first mooring section across the Weddell Sea began 1989 and was continued until 1995 and 1997 with one single mooring respectively. 2005 three of the longest continued mooring sites were deployed again in 2005 (Figs. 2.1 b, 2.13 and Tab. 2.7). The redeployed moorings AW1208 and AW1209 showed increasing temperature of the Weddell Sea Bottom Water (WSBW) in the central Weddell Sea. For this reason these mooring locations were continued. The instruments were focussed on the WSBW layer. Sea ice draft measurements with ULS were also continued at AW1208 and AW1207. Due to the weak currents in the centre of the Weddell gyre a RDI Longranger ADCP was installed in AW1208 at 300 m depth to support the estimates of the sea ice volume transport. All these moorings were equipped with sound sources at approximately 800 m depth - further details concerning the sound sources see section 2.1.6. The volume transport of the WSBW which flows northward along the continental slope has been previously calculated from moored records. After the break off from the Larsen Ice Shelf in 2002 the calculation should be repeated since significant changes might have occurred. For this reason additional moorings were deployed in the out flowing branch of the Weddell gyre from 900 m depth down the continental slope. Locations of these moorings were selected at the same sites as previous moorings (Fig. 2.16 and 2.15, Tab. 2.8). Fig. 2.12: Moorings recovered on the Greenwich meridian Fig. 2.13: Moorings recovered in the Weddell Sea Fig. 2.14: Moorings deployed on the Greenwich meridian Fig. 2.15: Moorings deployed in the Weddell Sea Tab. 2.5: Moorings recovered on the Greenwich meridian Mooring Latitude Water Date Instrument Serial Instr. Record Longitude Depth Time Type Number Depth Length (m) 1. Record (m) (days) last Record -------- ---------- ----- ----------- ---------- ------ ------ ------- AW1233-7 69°23.60'S 1950 17.02.2005 ULS 46 150 (2) 00°04.29'W 22:00 AVTP 11890 202 1117(2) 12.03.2008 ROM 11 100 699 1117 06:00 POD W402 1700 (1) SBE37 3810 1903 683 ROM 11 146 1904 1117 AW1232-8 68°59.75'S 3370 19.12.2005 ULS 50 125 (1) 00°00.16'W 20:00 ADOP 466 (1) 11.03.2008 AVTP 10492 745 812 04:00 AVT 6856 1804 812 SBE37 211 3312 812 AVT 9179 3313 812 AW1231-7 66°30.67'S 4517 18.12.2005 ULS 41 119 (1) 00°01.90'W 13:00 SBE37 249 150 810 07.03.2008 SBE37 2382 250 716 14:00 ADOP 385 309 (1) SBE37 2383 350 699 SBE37 2235 450 638 SBE37 2385 550 707 SBE37 2384 650 705 AVTP 9212 675 810 SQ W2-c30 865 AVT 9184 1777 810 SBE37 214 4472 810 AVT 9194 4473 810 AW1230-5 66°00.66'S 3450 08.02.2005 AVTP 9204 194 1123 00°11.28'E 21:00 SBE37P3 243 200 1123 08.03.2008 SBE37 233 300 1123 06:00 SBE37 232 400 1123 SBE37 235 500 1123 SBE37 236 600 (2) SBE37P3 2721 700 1123 AVTP 9214 701 (2) POD A401 1560 AVTP 9998 1597 1123 SBE37 238 3403 1123 ROM 11 25 3404 1123 AW1229-7 63°57.17'S 5180 16.12.2005 ULS 49 146 (1) 00°00.17'W 16:00 SBE37 2611 190 441 28.02.2008 SBE37 2386 290 733 10:00 ADOP 5848 373 (1) SBE37 1605 390 679 SBE37 2388 490 729 SBE37 2389 590 702 SBE37 1564 680 600 AVTP 9997 684 803 SQ W1-c29 832 AVT 9185 1982 803 SBE37 215 5135 803 AVT 9187 5136 803 Mooring Latitude Water Date Instrument Serial Instr. Record Longitude Depth Time Type Number Depth Length (m) 1. Record (m) (days) last Record -------- ---------- ----- ----------- ---------- ------ ------ ------- AW1227-9 59°04.11'S 4627 04.02.2005 AVTP 10003 231 1115 00°04.92'E 20:00 AVTPC 10926 723 1115 25.02.2008 SBE37PP10 1234 724 1113 12:00 AVT 11937 2019 1115 SBE37Pu 1603 4581 1113 AVT 9767 4582 1115 AW1228-7 56°57.56'S 3700 03.02.2005 AVTP 9763 191 1114 00°01.07'E 16:00 SBE37PuP3 1232 197 1114 23.02.2008 SBE37 441 247 1114 04:00 SBE37 442 297 1114 SBE37PuP3 1233 347 1114 AVTP 10539 401 1114 SBE37 447 403 1114 SBE37P3 247 582 1114 AVTP 8037 747 1114 SBE37PuP3 1230 749 1114 SBE37 444 998 1114 SBE37 440 1247 1114 ROM 11 214 2003 1114 ROM 11 26 3654 1114 SBE37Pu 1607 3656 1114 SBE26 257 3700 (1) AW1241-1 55°31.94'S 3810 02.02.2005 AVTPO 9200 212 11(2) 00°00.05'W 16:00 SBE37P3 246 317 1114 22.02.2008 AVTP 9785 424 1114 06:00 AVT 10532 770 1114 SBE16P3 245 772 1114 ROM 11 216 2017 1114 SBE37 269 2000 (2) ROM 11 219 3744 1114 SBE26 228 3810 (1) AW1238-5 54°30.76'S 1700 01.02.2005 AVTP 10541 201 1114 00°01.39'E 20:00 SBE16PuP3 1235 208 1114 21.02.2008 SBE37P3 244 257 1114 12:00 SBE37 218 306 1114 SBE37PP35 2719 356 1114 AVTP 9211 402 1114 SBE37PP35 2720 403 1114 SBE37 225 573 1114 AVTP 7727 748 1114 SBE37PP35 2722 750 1114 SBE37PP35 2723 1000 1114 SBE37 437 1250 1114 ROM 11 215 1644 1114 SBE37PP35 3811 1646 1114 SBE26 227 1700 (1) Tab. 2.6: Moorings deployed on the Greenwich meridian Mooring Latitude Water Date Instrument Serial Instr. Longitude Depth Time Type Number Depth (m) 1. Record (m) -------- ---------- ----- ----------- ---------- ------ ------ AW1232-9 68°59.74'S 3419 11.03.2008 ULS 57 150 00°00.17'E 14:00 AURAL 085 216 ADOP 6240 450 AVT 9782 750 ROM 11 144 1800 SBE37 2086 3300 ROM 11 486 3300 AW1231-8 66°30.68'S 4546 07.03.2008 ULS 56 150 00°01.81'W 22:00 SBE37 1236 200 SBE37 449 300 SBE37 2088 400 ADOP 825 450 SBE37 2089 500 SBE37 2090 600 SBE37Pu 1237 700 AVTP 10928 700 SQ 30 850 AVT 9180 1800 SBE37 237 4500 AVT 9186 4500 AW1230-6 66°01.13'S 3577 08.03.2008 AURAL 086 200 00°04.77'E 14:00 AVTP 3517 200 SBE37Pu 1229 200 SBE37 2091 300 SBE37 2092 400 SBE37 2093 500 SBE37 2094 600 SBE37Pu 2237 700 ROM 11 295 700 AVTP 9188 1600 SBE37 2099 3400 ROM 11 504 3400 AW1229-8 63°58.03'S 5195 28.02.2008 ULS 64 150 00°003.10'W 18:00 SBE37 2098 200 SBE37 2096 300 ADOP 5373 350 SBE16 2416 400 SBE37 2099 500 SBE37 2100 600 SBE37Pu 2396 700 AVTP 10925 704 SQ 29 850 AVT 9390 2000 SBE37 2101 5150 AVT 10499 5150 AW1227-10 59°04.10'S 4630 25.02.2008 SBE37P1O 1565 4580 00°04.88'W 14:00 Tab. 2.7: Moorings recovered along transect from Kapp Norvegia towards Joinville Island Mooring Latitude Water Date Instrument Serial Instr. Record Longitude Depth Time Type Number Depth Length (m) 1. Record (m) (days) last Record -------- ---------- ----- ----------- ---------- ------ ------ ------- AW1209-4 66°37.08'S 4860 01.03.2005 SBE37 3814 282 675 27°06.29'W 12:00 SQ W4 1840 18.03.2008 SBE16 319 4799 1113 12:00 SBE37 226 4848 1113 ROM 11 101 4849 1113 AW1208-4 65°37.14'S 4740 05.03.2005 ULS 42 154 (1) 36°23.53'W 21:00 ADOP 5691 291 (1) 21.03.2008 SBE37 241 296 1111 08:00 SQ W5/19 2014 SBE37 228 4678 1111 SBE37 1606 4728 1111 AVT 9182 4729 1111 AW1207-6 63°42.20'S 2500 14.03.2005 ULS 36 148 (1) 50°52.22'W 04:00 AVTP 9193 246 (2) 27.03.2008 SBE37 3812 248 681 14:00 AVT 10929 757 1109 POD 0403 1457 (1) SQ W6/17 2000 SBE37 239 2099 1109 SBE37 3813 2297 688 AVT 10497 2303 1109 SBE37 2097 2488 1109 AVT 10496 2489 1109 Tab. 2.8: Moorings deployed along transect from Kapp Norvegia towards Joinville Island Mooring Latitude Water Date Instrument Serial Instr. Longitude Depth Time Type Number Depth (m) 1. Record (m) -------- ---------- ----- ----------- ---------- ------ ------ AW1244-1 68°59.70'S 2927 13.03.2008 SQ 23 850 06°56.70'W 16:00 AW1245-1 69°03.68'S 4466 15.03.2008 SQ 24 850 17°25.89'W 16:00 AW1209-5 66°36.89'S 4864 18.03.2008 SBE 16 2415 300 27°07.08'W 20:00 SQ 34 800 SBE37P 220 4800 SBE37 230 4850 AW1208-5 65°36.85'S 4770 21.03.2008 ULS 62 150 36°24.43'W 16:00 ADOP 3813 300 SBE16 1979 300 SBE37 435 4680 SBE37 2234 4730 AW1217-3 64°23.63'S 4456 24.03.2008 SQ 32 850 45°52.38'W 14:00 SBE37 250 4150 SBE37 240 4350 ROM 11 296 4351 AW1216-3 63°54.03'S 3516 26.03.2008 SBE37 2392 3350 49°04.68'W 16:00 SBE37 2393 3400 SBE37 439 3450 ACM 11 298 3451 AW1207-7 63°42.74'S 2500 27.03.2008 ULS 60 150 50°50.55'W 20:00 AVTP 10872 250 SBE16 2414 251 AVT 10503 750 SQ 36 850 SBE37 2610 2100 SBE37 2297 2200 AVT 10530 2300 SBE37 436 2490 RCM 11 619 2490 AW1206-6 63°28.77'S 950 ULS 61 150 52°05.77'W AVTP 9206 250 SBE37 1228 500 AVT 9201 501 SBE16 2422 700 SBE37 438 900 RCM 11 508 901 Abbreviations: ADCP RD-Instruments, Self Contained Acoustic Doppler Current Profiler AURAL AURAL-Underwater Acoustic Recorder AVTCP Aanderaa Current Meter with Temperature-, Conductivity- and Pressure Sensor AVTP Aanderaa Current Meter with Temperature- and Pressure Sensor AVT Aanderaa Current Meter with Temperature Sensor RCM 11 Aanderaa Doppler Current Meter SBE16 SeaBird Electronics Self Recording CTD to measure Temperature, Conductivity and Pressure ULS Upward looking sonar from Christian Michelsen Research Inc. to measure the ice draft SBE37 SeaBird Electronics, Type: MicroCat, to measure Temperature and Conductivity SQ Sound Source for SO FAR-Drifter Remarks: Blank field: passive instrument with not data recording (1) Data recorded but not processed (2) Complete or partly missing data due to instrument failure Location and recovering of moored instruments Since ANT-XXI2 (2002) POSIDONIA has been proved as a reliable system to locate transponders or acoustic releases in moorings. POSIDONIA is an ultra short base line positioning system manufactured by iXSEA (France). The POSIDONIA signals can be detected even under unfavourable conditions, e.g. the high background noise created by Polarstern itself. Another advantage is the POSIDONIA transducer array which is installed in the moon pool. There the commands are transmitted from a fixed and stable platform resulting in a longer distance over which the signal can be received by the releaser because a handheld transducer lowered over the side vibrates while it is dragged through the water. It was observed that a mooring could not be released with the handheld transducer if the slant range is larger than 4,000 m while the same mooring was released with one single release ping only being sent via the POSIDONIA transponder array. During this cruise POSIDONIA was only able to display the relative target position because of a failure in the main electronic unit. Under good weather and sea ice conditions 11 of 12 moorings were recovered without any serious difficulties. The first try to recover the southernmost mooring AW1233-7 at the Greenwich section failed. One of the double releasers and an additional transponder in the mooring top were equipped with POSIDON IA- option but both could not be located while Polarstern was exactly at the estimated mooring position. Therefore the handheld transducer and the standard deck unit TT3O1 were used to interrogate the second releaser. This operation failed also. Several release commands were sent with POSIDONIA and TT3O1. An intensive search occurred from the bridge and with the helicopter downstream according to the observed sea ice drift. After 8 hours of searching the mooring was assumed as lost and Polarstern took course to the next working area. All moorings were equipped with an ARGOS satellite transmitter which is supposed to send the position if a mooring would surface unplanned. These messages were automatically checked by OPTIMARE and forwarded by email. By this we were informed that the ARGOS transmitter with the ID 10574 which was installed in AW1233-7 has sent one reliable position message. The position was about 9 km downstream off the deployed mooring location. Two additional locations obtained from OPTIMARE confirmed the position given in the email and indicated a slow westward drift. The time of the first message received by ARGOS agreed with the time when the release commands have been sent. Polarstern returned to the mooring guided the helicopter in a field of ice floes. Later the direction-finder detected the ARGOS signal too. Finally AW1233- 7 was recovered completely. The upper instruments and the mooring rope showed clearly the trace left by an iceberg. The rotor of the upper current meter was lost and the antenna of the ARGOS transmitter was pushed down through the fitting clamps. Therefore the antenna could not be stick out sufficiently of the water and only the satellite could receive the signal from above. The mooring had been hit and dragged off by an iceberg over a distance of more than 9 km and the release command was successfully received over a distance of about 10 km. Altogether the 12 moorings were equipped with 119 instruments. Five of them were sound sources. The instruments were recovered in good conditions. The data from 105 data memories were transferred to PC. The data processing occurred for 91 instruments on board. The processing of the remaining 14 data records from ULS, Bottom Pressure Recorder and ADCP could not finished on board but the data seemed to be in good condition. Six instruments failed which results in a data recovery rate of 94%. It was the first time moorings were deployed for a period of three years. Tab. 2.5 and 21 indicate that most of the instruments have measured and stored during the complete mooring period. While all Aanderaa current meter contained the full data rate the Seabird SBE37 have recorded approximately 80 % only. This is surprising because it happened for the moorings which have been exchanged in 2006 already. In the past SBE37 were working correctly for a period of two years with the same sampling setup. Therefore a bad quality of the batteries is the most probable reason. Another problem was related with SBE37 instruments with 5N38##. These instruments are a new design which have internal pumps in contrast to the former ones with external pumps. Probably the internal pump needs more power. In future SBE37 sample rates should be 60 minutes for old and new design. 2.1.5 Argo in the Southern Ocean Objectives The international Argo project maintains order of 3,000 profiling floats distributed throughout the world ocean, to establish a real-time operational data stream of mid- and upper (< 2,000 m) ocean temperature and salinity profiles. In addition, the array provides the mid-depth oceanic circulation pattern. During the past years, AWI achieved technological developments to extend the operational range of Argo floats into seasonally ice-covered regions. To this end and with additional support by the EU project MERSEA and the BMBF Project German Argo, the NEMO float (Navigating European Marine Observer) was developed and tested, which is now fully operational (Klatt et al., 2007). NEMO floats are equipped with ISA-2, an ice-sensing algorithm which triggers the abort of a floats' ascent to the sea surface, when the presence of sea ice is likely as determined from the existence of a layer of near surface winter water. To nevertheless be able to (retrospectively) track the floats that actively remained under the sea ice, acoustic tracking via RAFOS (Rossby et al., 1986) (Ranging And Fixing Of Sound) is used. All NEMO floats are equipped with RAFOS- receivers and an array of 10 moored sound sources has been installed. Work at sea Deployment of Argo floats During ANT-XXIV/3 a total of 15 NEMO floats (Navigating European Marine Observer, produced by OPTIMARE, Germany) and one refurbished APEX float (produced by Webb Research Corporation, USA) were deployed in the Weddell Sea. In addition, 38 APEX floats - also equipped with RAFOS and ISA - provided by Steve Riser, University of Washington (UW), were deployed. The instruments were launched at quasi-regular intervals along the Greenwich meridian and within the central and western part of the Weddell Sea proper, with preference given to undersampled regions and boundary currents (Fig. 2.16, Tab. 2.9 and 2.10). All of the float launches were preceded by a CTD cast. Fig. 2.16: Deployment positions of Argo floats. (White dots - APEX floats (University of Washington), red dots - NEMO floats (AWI), black dot - APEX float (AWI)) All APEX floats (UW and AWI) are is equipped with RAFOS Navigation System and with Ice Sensing Algorithm (ISA; abort-temperature -1.79°C). The AWI APEX and nine of the UW floats using the ARGOS system for communication (marked with an A in Tab. 2.9), the remaining 29 UW are capable of using IRIDIUM. The UW (AWI) floats were ballasted to drift at a depth of 1,000 m (800 m) and will acquire profiles from 2,000 m to the surface. Tab. 2.9: University of Washington APEX float launch positions and times. All floats (excluding the first are equipped with Aanderaa opt des for oxygen measurements. Float Station Latitude Longitude Date Time Depth Serial [PS71/] (UTC) (UTC) [m] Number ------ ------- ---------- ---------- -------- ----- ----- A 0051 101-6 42°20.74'S 8°59.13'E 14.02.08 03:42 4576 A 5171 102-1 44°39.64'S 7°05.43'E 15.02.08 11:05 4614 A 5285 103-2 45°59.86'S 5°52.86'E 16.02.08 04:05 3322 A 5287 104-10 47°38.44'S 4°16.56'E 17.02.08 14:41 4548 A 5281 106-2 48°54.72'S 2°47.90'E 18.02.08 06:30 4094 A 5283 107-4 50°16.98'S 1°27.98'E 18.02.08 22:39 3804 A 5282 108-4 51°29.97'S 0°00.02'W 19.02.08 11:52 2784 A 5280 110-2 51°56.75'S 0°00.84'E 19.02.08 17:45 2858 A 5288 112-3 52°30.23'S 1°23.75'W 20.02.08 03:28 2799 5326 122-2 56°00.65'S 0°00.96'E 22.02.08 16:50 3495 5327 125-3 56°58.03'S 0°01.02'E 23.02.08 08:33 3774 5323 127-2 57°29.90'S 0°01.20'E 23.02.08 14:45 4059 5313 128-2 58°00.49'S 0°00.12'W 23.02.08 23:07 4528 5318 130-2 58°29.92'S 0°00.09'W 24.02.08 07:36 4187 5307 132-4 59°04.30'S 0°05.60'E 25.02.08 14:04 4662 5302 134-2 59°31.00'S 0°02.03'E 25.02.08 20:49 4780 5320 135-2 60°00.46'S 0°00.21'W 26.02.08 04:19 5344 5321 137-2 60°29.93'S 0°00.04'W 26.02.08 11:18 5355 5308 138-2 61°00.13'S 0°00.48'E 26.02.08 18:47 5379 5298 140-2 61°29.88'S 0°00.48'W 27.02.08 01:43 5377 5325 141-3 61°59.97'S 0°00.03'E 27.02.08 09:27 5358 5324 143-3 62°30.58'S 0°00.54'W 27.02.08 17:31 5337 5301 144-2 63°00.06'S 0°00.28'E 28.02.08 00:34 5302 5295 146-2 63°29.97'S 0°00.20'E 28.02.08 07:40 5236 5331 149-2 64°30.10'S 0°00.12'E 29.02.08 04:35 4659 5303 157-6 66°28.31'S 0°01.73'W 08.03.08 00:45 4493 5310 159-5 66°01.43'S 0°07.81'E 08.03.08 15:10 3549 5300 163-2 67°00.03'S 0°00.11'E 09.03.08 17:09 4702 5329 167-3 68°00.00'S 0°00.06'W 10.03.08 07:30 4506 5330 171-2 68°45.11'S 0°00.09'E 10.03.08 18:27 3622 5317 192-2 66°56.75'S 25°17.07'W 17.03.08 22:03 4852 5316 194-2 66°24.79'S 29° 1.05'W 19.03.08 20:39 4827 5304 195-2 66°13.03'S 30°55.86'W 20.03.08 04:49 4810 5311 196-2 66° 0.48'S 32°46.68'W 20.03.08 12:55 4789 5305 197-2 65°48,54'S 34°37.55'W 20.03.08 21:01 4787 5306 198-6 65°36,63'S 36°22.87'W 21.03.08 14:51 4770 5299 199-2 65°27.20'S 37°42.44'W 21.03.08 21:47 4731 5309 200-2 65°16.92'S 39° 1.09'W 22.03.08 04:05 4766 All NEMO floats are equipped with RAFOS Navigation System, an adjustable Ice Sensing Algorithm (ISA-2), set to -1.79'C with a 'retarded' response: Once activated, ISA-2 will need to detect 'surfacing conditions' (i.e. the lack of 'abort conditions') for two consecutive ascent cycles, before giving the float permission to completely ascend to the surface on the second cycle. An interim data storage (iStore) stores any profiles that could not be transmitted in real time due to ISA aborts and transmits these profiles during ice-free condition. The floats were ballasted to drift at a drift depth of 800 m and will acquire profiles from 2,000 m to the surface. Tab. 2.10: AWI float launch positions and times. All floats were equipped with Ice Sensing Algorithm ISA-2, set to -1.79'C. Floats #120 - 134 are NEMO floats, float #135 is an APEX float. FLOAT AWI SERIAL ARGOS WMO # STATION LATITUDE LONGITUDE DATE TIME DEPTH # # -DEC [PS71/] [S] (UTC) (UTC) [m] --- ------ ----- ------- ------- --------- ---------- -------- ----- ----- 120 55 10120 7900232 147-4 63°58.04' 00°02.44'W 28.02.08 21:33 5196 121 49 08064 7900226 150-3 64°59.99' 00°00.01'E 29.02.08 11:00 3726 122 46 29223 7900224 152-3 65°29.97' 00°00.36'E 29.02.08 17:22 3972 123 25 27983 7900218 158-2 66°14.72' 00°01.22'W 08.03.08 04:39 3684 124 50 08067 7900227 161-7 66°30.07' 00°00.01'E 09.03.08 10:27 4546 125 54 09728 7900231 165-2 67°30.03' 00°00.10'E 10.03.08 00:18 4625 126 40 08060 7900223 169-2 68°30.05' 00°00.14'E 10.03.08 13:56 4256 127 36 28037 7900222 175-5 68°59.82' 00°00.14'E 11.03.08 13:29 3413 128 27 27985 7900219 184-3 68°59.59' 06°56.73'W 13.03.08 14:29 2924 129 58 08058 7900234 186-4 69°03.80' 17°26.53'W 15.03.08 15:24 4766 130 51 09354 7900228 188-2 68°23.55' 19°04.26'W 16.03.08 08:48 4827 131 31 28013 7900221 189-2 67°56.47' 19°59.98'W 16.03.08 17:53 4905 132 52 09355 7900229 190-2 67°35.84' 21°47.97'W 17.03.08 03:13 4904 133 56 10454 7900233 191-4 67°18.96' 23°38.27'W 17.03.08 14:10 4874 134 53 09363 7900230 193-12 66°34.66' 27°25.22'W 19.03.08 13:28 4861 135 2552 9356 7900235 207-4 64°23.06' 45°55.58'W 24.03.08 16:13 4442 2.1.6 Installation of RAFOS Sound sources During this cruise, 5 sound sources were recovered and 7 sound sources deployed (Fig. 217, Tab. 211 and 212). Fig. 2.17: Current state of the Weddell Sea RAFOS array. Red dots depict positions where sound sources were deployed or redeployed during ANT-XXIV/3. The black dots represent positions of sound sources deployed during earlier cruises. At locations Wi and W2, the recovered sources were immediately redeployed after a battery and clock check and the exchange of shackles and chains. At locations W4 and W6 the recovered sound sources (tuned to a deployment depth of 2,000 m) have been replaced by two new sources (tuned to a deployment depth of 800 m). Sound source W5 was flooded and has not been replaced. Finally, on three locations (W9, Wi 0, and Wi 1) sound sources have been deployed for the first time. Tab. 2.11: Sound sources recovered 1) Note that for R29 and R30 the sources internal software attempts to compensate for the noted clock drift by adjusting the pong schedule. To be able to determine the effective drift of the pongs, this adjustment needs to be accounted for. The necessary information can only be retrieved after the next recovery of the sources by reading the operations log file as stored on board the source. Note the difference between GPS and UTC times. site / position sound source status mooring water depth pong time recovery date --------- ------------- ---------------------------------------------- Wlc/229 63°57.17'S R29 @ 832 m; piggy-back, aluminum resonator 00:30 GPS 00°00.17'W RTC 12:28:16 @ GPS 12:35:00 -> 392s late(1) 5180 m general status at recovery: ok 28 Feb 2008 Vbat-2 = 8.56 Vdc 12:07 UTC High Voltage = 19.24 Vdc Internal Pressure = 203.48 hPa W2c/231 66°30.67'S R30 @ 865 m; piggy-back, aluminum resonator 01:00 GPS 00°01.90'W RTC 17:04:34 @ GPS 17:08:00 -> 206s late(1) 4517 m general status at recovery: ok 07 Mar 2008 Vbat-2 = 8.57 Vdc 16:50 UTC High Voltage = 19.67 Vdc Internal Pressure = 294.60 hPa W4a/209 66°37.08'S R16 @ 1840 m; in-line design, steel resonator 01:30 27°06.29'W status: flooded 4860 m Vbat-2 = - 18 Mar 2008 High Voltage = - 16:09 UTC Internal Pressure = - W5a/208 65°37.14'S R19 @ 2014 m; in-line design, steel resonator 00:30 36°23.53'W RTC 10:59:24 @ G PS 10:57:00 ->144s early 4740 m general status at recovery: dry, CPU ok, no 21 Mar 2008 pongs 08:20 UTC Vbat-2 = 7.7 (with Voltmeter, 1? puck) High Voltage = 3.7 (with Voltmeter, 5 pucks) Internal Pressure = ok but no pressure gauge W6a/207 63°42.20'S R17 @ 2000m; in-line design, steel resonator 01:00 50°52.22'E RTC: pending 2500 general status at recovery: pending pending Vbat-2 = pending Pending High Voltage = pending Internal Pressure = pending Tab. 2.12: Sound source moorings of ANT-XXIV/3. Sound source depths are nominal depths according to preliminary mooring protocols. Note the difference between GPS and UTC times. site / position sound source status mooring water depth pong time deployment date --------- ------------- ---------------------------------------------- W1d/229 63°58.03'S R 29 @ 820 m; piggy-back design, aluminum 00:30 GPS 00°03.10'W resonator 5170m toffset =0s 28-02-2008 Vbat-2 = 8.56 Vdc 17:31 High Voltage = 19.24 Vdc Internal Pressure = 203.48 hPa W2d/231 66°30.68'S R 30 @ 869 m; piggy-back design, aluminum 01:00 GPS 00°01.81'W resonator 4517 m Vbat-2 = 857 Vdc 07-03-2008 High Voltage = 19.67 Vdc 21:24 Internal Pressure = 294.60 hPa W11a/244 68°59.10'S W 23 @ 790 m; piggy-back design, aluminum 00:40 GPS 06°56.10'W resonator 2927m Bat=+00439dV 13-03-2008 Vac=+00044 14:14 W9a/245 69°03.68'S W 24 @ 800m; piggy-back design, aluminum 01:10 GPS 17°25.89'W resonator 4766 m Bat=+0044idV 15-03-2008 Vac=+0004i 14:49 W4b/209 66°36.89'S R 34 @ 837 m; piggy-back design, aluminum 01:30 GPS 27°07.08'W resonator 4860m Vbat-2=8.11 Vdc 18-03-2008, High Voltage = 20.39 Vdc 19:48 Internal Pressure = 661.86 hPa W10/217 64°23.36'S R 32 @ 836 m; piggy-back design, aluminum 00:40 GPS 45°52.38'W resonator 4400 m Vbat-2 = 849 Vdc 24-03-2008 High Voltage = 27.49 Vdc 12:37 Internal Pressure: 991.15 hPa (sensor faulty, manual vacuum check Ok. W6/207 63°45.10'S R 36 @ 857 m (as planned) 01:00 GPS 50°54.30'E with electronics R 19 2500 m Vbat-2 = 8.98 Vdc (as measured by #36) depi. pending High Voltage = 20.55 Vdc (as measured by #36) Internal Pressure = no sensor. (Manual vacuum check Ok Preliminary and expected results The deployment 54 ARGOS floats into the Weddell Gyre increases significantly the number of active floats from 32 to 86. Thus, for the first time the requirements of the Argo project (floats spaced every 3°) are met (Fig. 2.18). Fig. 2.18: Current distribution of Argo floats in the area of the Weddell gyre References Klatt, O., Olaf Boebel, and E. Fahrbach, 2007: A profiling float's sense of ice. Journal of Atmospheric and Oceanic Technology, 24, 1301-1308. DOI: 10.1175/JTECH2026.1 Rossby, T., D. Dorson, and J. Fontaine, 1986: The RAFOS-System. Journal of Atmospheric and Oceanic Technology, 3, 672-679. 2.1.7 Iceberg tracking To estimate the fresh water transport by icebergs, satellite tracked transmitters were deployed since cruise ANT-XVI/2 as iceberg markers. The project was supposed to end with a last deployment during cruise ANT-XXII/2 but one remaining transmitter was deployed during this cruise. The marker determines its position once per day at noon with a GPS receiver. The positions are transmitted via satellite using the ARGOS system. The ARGOS transmitter is switched on for 6 hours once a week, to send the positions from the past seven days. The transmitter's on-time lasts long enough to ensure that all data can be received by CLS in Toulouse, France. This weekly transmission mode was chosen to save CLS service costs. The iceberg markers are designed to operate for up to two years. Due to environmental aspects, the housing is slightly enlarged compared to previous versions. Thus the new markers have positive buoyancy. Markers from melted icebergs are likely to leave the Antarctic Ocean by drifting northwards and being entrained into the Antarctic Circumpolar Current. Tilt sensors are installed to detect when an iceberg begins to capsize. The ARGOS transmitter will switch into a continuous mode as soon as the tilt exceeds a fixed limit. The markers were deployed on icebergs by helicopter. A digital photograph was taken to describe the shape of the iceberg. The length and width was measured with the GPS, flying along and across the iceberg. The height above sea level is taken from the radar altimeter of the helicopter. Tab. 2.13 gives of the marked iceberg. OPTIMARE, Bremerhaven, is assigned to collect the data from CLS via direct computer link and to process and validate the data. Tab 2.13: Deployment of iceberg tracking ARGOS transmitter Transmitter Iceberg ------------------------------- --------------------------- ARGO Date Time Latitude length width Freeboard(m) S ID (UTC) Longitude (m) (m) ---- ------- ----- --------- ------ ----- ------------ 9802 24.3.08 13:00 64°32.4'S 500 330 30 45°47.6'W Fig. 2.19: Track of the iceberg with marker Id 9802 2.1.8 Sea ice observations Sea ice observations were conducted on an hourly basis by the CTD watch from the bridge of Polarstern from 2 March to 29 March 2008 during daylight conditions (ca. from 05:00 to 21:00 UTC) when the ship was steaming. They are a contribution to the Antarctic Sea Ice Processes and Climate (ASPeCt) programme, which aims at an improved understanding of the role of Antarctic sea ice in the global climate system. The sea ice thickness data collected in this framework form the only circumpolar ice thickness dataset available for the Southern Ocean and have been used for model validation studies. According to the ASPeCt protocol, total ice concentration, and the thickness, concentration and morphology (ridge height, areal fraction of ridged ice, floe size; snow thickness) of the three dominant ice types within a 1 km radius from the ship were recorded while the ship moved through the pack ice. The observations were complemented by records of sea surface temperature, near-surface air temperature, wind speed and direction, and total cloud cover. All together 236 observations were carried out, at 167 of them ice was encountered. All data collected were sent to the ASPeCt database immediately after the cruise. As the cruise was conducted in austral summer, during the time of minimum ice extent, rather little sea ice was encountered. On our way to Neumayer Station no significant ice cover was encountered until we reached the coast. However, the sea ice conditions in the Weddell Sea were extreme. Over the summer two large ice tongues stretched from the southern to the northeastern and the northwestern Weddell Sea (Fig. 220). This wider than normal ice extent is consistent with a trend visible in the time series of NSIDC derived from satellite images of increasing sea ice extent in summer during the last decades. However, this does not mean a real increase but only a weaker melting in summer because the winter sea extent remained basically constant. It is of special interest, that the evaluation of satellite data by NSIDC indicated clearly that the Antarctic summer 2007/2008 was the one with the largest ice extent on record. This trend which is particularly strong in the Atlantic sector of the Southern Ocean is in clear contrast to the Arctic where a strong decrease of the summer ice extend is observed. To understand the opposing trends in the Antarctic and the Arctic is an obvious aim of our cruise. Fig. 2.20: Regional sea ice distribution in the Weddell Sea on 18 March 2008 (www.seaice. de) 2.2 TRANSPORT VARIATIONS OF THE ANTARCTIC CIRCUMPOLAR CURRENT Carmen Böning, Olaf Boebel and Olaf Klatt Alfred-Wegener-Institut Objectives Pressure Inverted Echo Sounders (PIES) deliver bottom pressure, bottom temperature and travel times of sound signals from the bottom to the sea surface, effectively providing a measure of average temperatures, bottom temperature and pressure variations and sea surface height. PIES data are used to extract transport variations of the ACC as part of the AWI programme to observe the decadal variability of the Antarctic Circumpolar Current (ACC). PIES are placed along the GoodHope section between South Africa and Antarctica, which in large parts coincides with satellite ground track # 133 of the Jason (previously TOPEX/Poseidon) satellite mission to allow direct comparison with altimetry data. PIES to PIES distances are selected to allow resolution of the major oceanic fronts of this region. In addition, the same PIES data is used in the context of the GRACE satellite mission (Gravity Recovery And Climate Experiment), to validate monthly mean ocean bottom pressure anomalies as derived from the GRACE geoid variations. As the typical length scale inherent to GRACE data is about 1,000 km, the broad spatial coverage of the GoodHope PIES array (spanning nearly 2,000 km) is well suited to determine the accuracy of the GRACE measurements in this region. Additional PIES complement the array to the northwest. Work at sea Several of the PIES deployed from Polarstern in 2005/6 required an exchange in 2008 to prevent the loss of the instruments due to a hardware error which was discovered only after the instruments' deployment and which would lead to early battery depletion. While 6 positions of the GoodHope and Grace PIES arrays were served by Polarstern, the 3 remaining sites were covered by the G.O. Sars during the 2007/8 AKES cruise. Tab. 2.14: PIES recovery. Clock offsets are positive if early with regard to UTC/GMT. *) PIES release/checkout from helicopter moor station PIES start launch launch lat release surface surface lat depth Clock -ing book Sn. date & date & & Ion date & date & & Ion [m] offset (rel.) time time time time [UTC] [UTC] [GPS] [GPS] ---- ------- ---- -------- -------- ---------- -------- -------- ----------- ----- -------- ANT- PS 71/ 189 25.08.06 26.08.06 37°05.56'S 11.02.08 11.02.08 37°04.09'S 4977 -165 sec 3-1 097-1 15:06 15:13 12°46.16'E 09:42* 11:25 12°48.79'E 11.02.08 13:52:15 ANT- PS 71/ 113 26.01.05 26.01.05 41°08.12'S 13.02.08 13.02.08 41°08.56'S 4650 +99 sec 5-1 099-3 16:12:56 19:20 09°56.62'E 03:43 05:35 09°57.18'E 16.02.08 16:16:21 ANT- PS 71/ 135 26.01.05 27.01.05 44°39.86'S 15.02.08 15:02.08 44°39.48'S 4536 +113 sec 7-2 102-3 22:50:59 20:37 07°04.96'E 07:57 09:45 07°05.71'E 15.02.08 12:36:00 ANT- PS 71/ 125 29.01.05 30.01.05 47°39.30'S 17.02.08 17.02.08 47°39.23'S 4536 +78 sec 9-1 104-7 17:06:12 02:29 04°15.70'E 11:32 13:14 4°16.11'E 17.02.08 15:29:00 ANT- PS 71/ 185 24.10.06 24.10.06 50°15.73'S 18.02.08 18.02.08 50°15.47'S 3888 Lost 11-2 107-2 17:46:47 20:24 01°25.95'E 18:15* 19:48 1°26.31 E ANT- PS 71/ 069 22.10.06 24.10.06 52°30.47'S 20.02.08 20.02.08 52°30.24'S 2736 -65 sec 13-1 112-2 14:58:12 06:17 01°25.12'W 02:09 02:52 01°22.27'W 20.02.08 11:30:30 During ANT-XXIV/3, 5 of 6 PIES were successfully recovered (Tab. 214) while one was lost during recovery. This PIES (#185 of mooring ANT-1 1.2) was lost after it had successfully surfaced. It floated next to the ship to be retrieved when it drifted astern and probably got smashed under the ships stern due to wave action. Tab. 2.15: Helicopter assisted PIES recoveries. Sonobuoys were dropped from a helicopter from a height of 1000 ft and acoustic data recorded via radio link. Data dropouts are probably due to shielding of the antenna by the helicopter's fuselage. 12 and 12.5 kHz pings are generated by the PIES and release units mooring Sonobuoy launch date Sonobuoy records water site launch & time depth lat & lon [GPS] [m] ---------- ---------- ----------- -------------- ----------------- ----- ANT-3-1 37°05.56'S 11.02.08 channel 5 none (user error) 4977 12°46.16'E 09:42 (received) ANT-5-1 41°08.12'S 12.02.08 channel 7 17:17 - 17:42 4650 09°56.62'E 17:17 (received) ANT-11-1-2 50°15.73'S 18.02.08 channel 5 18:04 - 18:29 3888 01°25.95'E 18:04 (failed) channel 8 (ok) At two sites, PIES releases were executed some 20 nm ahead of Polarstern via an hydrophone lowered from a helicopter hovering above the water. During these, and on a third site, the PIES acoustic activity was monitored previous to and during release via sonobuoys, kindly provided by the Forschungsanstalt for Wasserschall und Geophysik, Kiel, Germany, dropped from the helicopter (Tab. 2.15). Details of this procedure are described in the cruise report of ANT-XXII/3. In this context it was particularly useful to have the PIES transmission schedules set to 10 minutes intervals for rather than half hourly, for acoustic verification. Fig. 2.21: Positions of PIES deployments during Polarstern cruise ANT-XXIV/3 (white dots) and G. 0. Sars cruise AKES 2 (yellow dots). Red circles indicate PIES with PopUp buoys attached. Red line: ground track #133 of Jason satellite mission (previously TOPEX/Poseidon). White dotted lines: nominal positions of fronts: STF = Subtropical Front, SAF = Subantarctic Front, PF = Polar Front, SACCF = Southern Antarctic Circumpolar Current Front. White cross: recovery site of PIES at position ANT- 13.1, re-deployment at position ANT- 13.2 on Greenwich meridian. Three of the PIES were re-deployed after refurbishment on board (exchange of batteries, software upgrades and hardware fixes). Along with additional deployments of two new PIES, a total of 5 PIES was deployed across the ACC (Tab. 2.16 and Figs 2.21 and 222) at sites ANT-5, 7, 9, 11, and 13. At site ANT-3, a PIES (#192) with two PopUps was successfully deployed by G.O.Sars, only hours after Polarstern recovered the mooring ANT-3.1 at the same position. Tab. 2.16: PIES deployments moor- Station PIES start launch launch POSIDONIA: POSIDONIA: POS. depth PopUp Auto Ing book S/N date & date & lat & lon bottom bottom lat ID [m] release (deploy) time time date & & lon date & [GPS] [GPS] time time [GPS] [UTC] ---- -------- ---- -------- -------- ---------- --------- ---------- --- ----- ----- -------- ANT- PS 062 10.02.08 13.02.08 41°07.35'S 13.02.08 41°07.4'S 470 4675 - 12.02.12 5-2 71/99-1 15:29 01:50 9°57.32'E 02:10 09°57.70'E - 12:00 ANT- PS 184 13.02.08 15.02.08 44°38.90'S no 44°39.65'S 387 4616 #5 14.02.12 7-3 71/102-1 15:54 05:37 7°05.91'E reception 07°06.20'E #19 04:15 ANT- PS 113 16.02.08 17.02.08 47°39.41'S no 47°39.35'S 388 4538 - 17.02.12 9-2 71/104-5 16:20 09:42 4°15.69'E reception 04°15.70'E - 02:00 ANT- PS 189 18.02.08 18.02.08 50°15.47'S 18.02.08 50°16.12'S 386 3844 #14 18.02.12 11-3 71/107-2 20:55 19:20 01°26.33'E 20:08 01°26.72'E #18 02:00 ANT- PS 125 19.02.08 21.02.08 53°31.25'S 21.02.08 53°31.19'S 471 2632 - 20.02.12 13-2 71/115-1 14:37 01:13 00°00.09'E 01:45 00°00.23'E - 02:00 Fig. 2.22: Hydrosweep depth profile (black) along ground track #133 (obtained during ANTXXII/3) with a resolution of 1,000 m. Red dots indicate PIES positions ANT-3, -5, -7, -9, -11, and -13. The grey curve indicates topography according to Smith and Sandwell TOPEX/Poseidon analysis. Preliminary results From four of the five successfully recovered PIES continuous time series with half hourly data were obtained. PIES #189, recovered at site ANT-3, shows data gaps of a few cycles (up to days) in the beginning of the measurement and has a large gap of one and a half month starting in the middle of December 2006. Examination of the log-file revealed unknown problems to have caused repeated self-resets of the instruments CPU. After 4 May 2007 however, the PIES operated flawlessly and provided half hourly measurements until its recovery on 11 February 2008. PIES #185, which had been lost during recovery, had fortunately previously transmitted some of its data via a PopUp buoy, so 6 data-months of the 18 data-months record are available. Pressure time series of all instruments show a clear tidal signal and the fortnightly modulation of the tides (Fig. 223). On a monthly time scale, the variability of the pressure time series measured at positions south of ANT-3 is of about 0.05 to 0.1 dbar, decreasing from North to South. This range compares well with the range of variability as derived from (satellite based) GRACE solutions. The highest bottom pressure variability of about 1 dbar was found at site ANT-3, and is caused by the substantial sea surface height difference of more than 1 m between cyclonic and anticyclonic eddies, which are omnipresent in the Cape Basin. Three of the bottom pressure time series, however, show conspicuous drifts, which have not yet been removed and need to be analysed in more detail in the lab. Fig. 2.23: Absolute pressure, temperature anomalies and travel time measured by PIES #113 at ANT-5. 1. Blue: unfiltered 30-min values. Red: 2-day low pass filter. Yellow: 30-day low pass filter. Black: 180-day low pass filter. The observed range of the bottom temperature anomalies is, on a daily time scale, ± 0.01°C. On longer time scales, the time series show a period of 10 - 14 months and about half the amplitude. Fig. 2.24: Blue dots indicate the position of the POSIDONIA transponder during the recovery (top) and deployment (bottom) at ANT-5. Red line: release signal sent The acoustic travel time varies by up to 0.02 sec on time scales typical for mesoscale features. Those instruments moored at depths of 4000-5000 m showed clear travel time signals (and did hence well receive the acoustic pings), while PIES #69, moored at a depth of 2736 m, provided a diffuse travel time signal only. Further analysis of this instrument will be needed to resolve if this was due to the PIES electronics or rather a depth-related issue. Tab 2.17: PIES ascent or descent and buoyancy information Position R/D PIES Posi- Posi- w release release Anderaa Floata- Buoy- S/N donia donia [m/s] sent DCS tion ancy S/N data -------- --- ---- ----- ----- ----- ---------- ---------- ------- ------- ------ ANT-3-1 R 189 470 n n j 19 ANT-5.2 D 62 470 j 1.01 n j -35.34 ANT-5.1 R 113 387 j -0.84 13.02.200 13.02.200 n n 16 8 03:43:00 8 04:00:00 ANT-7.3 D 184 387 j 1.12 S/N 753 j -45.34 ANT-7.2 R 135 388 j -0.8 15.02.200 15.02.200 n n 16 8 07:57:00 8 08:13:00 ANT-9.1 R 125 386 n n n 16 ANT-9.2 D 113 388 j 1.26 n n -60.34 ANT-11.2 R 185 462 n n n 16 ANT-11.3 D 189 386 j 1.38 n n -70.34 ANT-13.1 R 69 471 j not 20.02.200 not n n 16 valid 8 02:09:00 valid ANT-13.2 D 125 471 j 1.36 n n -60.34 Critical to the planning of helicopter assisted PIES releases, but also to the overall expedition planning, are times of ascent and descent when instruments are deployed and recovered, respectively. To obtain quantitative estimates of these times for the various PIES/PopUp configurations used, range information (Fig. 224) from POSIDONIA transponders (which are part of all PIES moorings) have been analyzed in detail (Tab. 217), showing descent speeds to range from 1 to 1.4 ms(^-1). A generalized approach, showing the descent speed as a function of system weight (Fig. 225 upper left corner) allows prediction of descent time for future deployments of variable total weight. Released PIES without additional floatation attached showed an ascent speed of 0.8 to 0.84 ms(^-1). Fig. 2.25: Speed of ascent and descent and of PIES' as a function of system configuration 2.3 MONITORING THE ACC TRANSPORT THROUGH DRAKE PASSAGE Christine Provost(1), Jae Hak Lee (2), (1)LOCEAN Michael Beauverger(1), Annie Kartavtseff(1), (2)KORDI Hervé Legoff(1), Thierry Monglon(1), Sang Chul Hwang(2) Objectives The Antarctic Circumpolar Current (ACC), the world largest current, is a key element of the global climate system. The ACC is constricted to its narrowest extent (700 km) in Drake Passage thus a convenient place for observations. Monitoring the transport and water mass characteristics of the ACC is essential for understanding the coupling of this major current with climate change. It is not an easy matter since the current is concentrated in highly variable narrow bands of swifts currents and energetic eddies of all sizes are numerous. Our experimental set up is designed to use the complementarity between satellite and in-situ observations. Satellite altimetry measures the sea level of the ocean along tracks every 10 days with horizontal resolution of 7 km. The in-situ measurements will provide information on the vertical structure of the ocean, information that cannot be obtained by satellites. During ANT-XXII/3, in January-February 2006, we deployed an array of 10 current meter moorings along a ground track of Jason altimetric satellite (Fig. 226). Fig. 2.26: Location of the 10 moorings deployed during ANT-XII/3 in January February 2006. Background is bottom topography (in m). The narrow ridge to the south west of M6-M7, part of the Shackleton Fracture Zone, constrains the ACC flow. Work at sea The work at sea included: recovery of the moorings deployed in 2006 (Tab. 2.18), deployment of 5 new moorings (Fig. 227 and 2.28, Tab. 2.19) at the locations Ml through M5 where the Antarctic Circumpolar Current is canalized due to the steep and narrow ridge of the Shackleton Fracture Zone and realization of a refined array of CTD stations with LADCP along the satellite ground track. The two moorings to the south M10 and M9 which were equipped with double benthos releases were safely recovered. The remaining 8 moorings carried a transducer equipped with POSIDONIA (Ml through M8) and could be located readily. However two of them M2 and M8 could not be recovered. They were released, the acoustic transducers went up from their moored positions (respectively 3,070 m for M2, 2,600 m for M8) and then stabilized around 1,200 m at M2 and 1,600 m at M8. In both cases, the moorings, once stabilized, began to drift with the current. In spite of dredging efforts (1 full day for M8, and more than half a day for M2) the two moorings could not be recovered. During the two attempts wind and sea surface state conditions were rather poor. M7 slowly went up to the surface. We recovered it and discovered that part of the foam flotation had imploded. M6, M5, M4, M3 and Ml were fully recovered. The instruments were read on board. Tab. 2.18: Data recovered Mooring Instrument Depth record CTD/LADCP stations ------- ---------- ------ -------------- --------- Ml ADCP 200 m 26 months PS71/252 Aquadopp 500 m 26 months PS71/253 RCM8 500 m 26 months Microcat l000 m 26 months RCM11 l000 m 26 months M2 lost M3 ADCP 400 m 26 months PS71/248 microcat 400 m 26 months PS71/249 Aguadopp 900 m 26 months RCM8 900 m 26 months RCM8 1950 m 26 months MORS 3100 m 26 months M4 RCM8 400 m 26 months Microcat 400 m 26 months PS71/244 Aguadopp 950 m 26 months RCM7 950 m 26 months RCM8 2450 m 26 months M5 Aguadopp 500 m 0 (head lost) PS71/241 MORS 550 m 26 months Microcat 1070 m 26 months RCM7 1070 m 26 months RCM8 2640 m 26 months M6 Aguadopp 300 m 26 months PS71/237 MORS 300 m 26 months microcat 800 m 26 months RCM7 800 m 26 months RCM8 2440 m 26 months M7 Aguadopp 450 m 0 (crushed) RCM7 450 m 21 months PS71/236 microcat 950 m 21 months RCM8 950 m 21 months RCM8 2540 m 26 months M8 Lost M9 RCM-8 500 m 0 (leak) RCM-11 1000 m 26 months PS71/230 RCM-11 2500 m 26 months M10 RCM-11 500 m 14 months PS71/226 RCM-11 1000 m 26 months RCM-11 1500 m 11 months Tab 2.19: Moorings deployed Mooring Instrument Depth CTD/LADCP stations -------------------- ---------- ------ ------------------ M1-2: ADCP 500 m PS71/252 12/04/2008 18:00 UTC PS71/253 Lat: 55°10.16'S microcat 500 m Lon: 65°11.22'W Aguadopp 500 m Depth: 1600 m microcat 1000 m Aguadopp l000 m M2-2: microcat 500 m PS71/256 13/04/2008 15:50 UTC Aguadopp 500 m Lat: 55°43.135' microcat l000 m Lon: 64°24.100'W Aguadopp l000 m Depth: 3816 m RCM-8 2000 m RCM-8 3000 m M3-2: ADCP 500 m PS71/248 10/04/2008 20:18 UTC microcat 505 m PS71/249 Lat: 56°06.05' Aguadopp 510 m Lon: 63°43.93' microcat 1000 m Depth: 4275 m RCM-7 1000 m RCM-8 2000 m RCM-8 3000 m M4-2 RCM-11 500 m Super station 08/04/2008 22:24 UTC RCM-11 1500 m DRAKE-4 Lat: 56°55.55'S RCM-11 2500 m PS71/244 Lon: 62°22.03'W Depth: 4093 m M5-2 RCM-11 500 m Super station 07/04/2008 15:36 UTC RCM-11 1500 m DRAKE-3 Lat: 57°37.53'S RCM-11 2500 m PS71/241 Lon: 60°55.01'W Depth: 3445 m Fig. 2.28: Moorings deployed in Drake Passage 2.4 MEASUREMENTS OF TRACE GASES: CHIOROFLUOROCARBONS, HELIUM ISOTOPES & NEON Madlen Gebler, Alexandra Gronholz, Oliver Huhn UP, Bremen Objectives The Weddell Sea is a major supplier for Antarctic Bottom Water to the World Ocean. There, Weddell Sea Deep and Bottom Water (WSDW and WSBW) are formed by interaction of mid-depth water masses with several shelf water types (e.g., Ice Shelf Water, ISW, or glacial melt water) and by entrainment of external water masses. Modifications in its composition and formation rates - caused by environmental changes (e.g., decay of ice shelves, warming mid-depth water) - could modify the strength of the Meridional Overturning Circulation (MOC) and, thus, affect climate and climate change. Changes in the formation processes and in the amount of formed deep and bottom water might also influence the uptake and storage of carbon in the interior of the Southern Ocean. The major aims of our tracer measurements are: • To assess the formation rates and its variability of WSDW and WSBW. • To consider correlations to changing environmental conditions (i.e. degradation of ice shelves, enhanced melting, warming, freshening) that might lead to varying deep and bottom water composition, distribution, and formation rates • To determine the variability of deep and bottom water export and import from easterly sources across the Greenwich meridian. • To assess the contribution and variability of Southeast Pacific Deep Slope Water (SPDSW) through Drake Passage to the total transport of the Circumpolar Current. The deep and bottom water formation and its variability in the Weddell Sea will be studied by using chlorofluorocarbon (CFC) inventories and CFC based transit time distributions (TTD5, ore age spectra), inferred from this cruise and from historical data. The combined hydrographic, CFC and noble gas data will allow to distinguish different source water masses, that contribute to deep and bottom water formation, and how they reflect changing environmental conditions. From the continuation of the CFC time series along the Greenwich meridian, further insight regarding the variability of the export of deep and bottom water out of the Weddell gyre and through the South Scotia Ridge system as well as the import from easterly sources is expected. The role of the SPDSW in the Atlantic Circumpolar Current will be studied by the repeated noble gas, CFC, and velocity observations across Drake Passage. Work at sea During the cruise a total of 1620 samples on 97 CTD/water bottle stations were collected for chlorofluorocarbons (CFC-1 1 and CFC-1 2); 32 stations were occupied along the Greenwich meridian section, 37 stations along the Weddell Sea section, and 28 stations across the Drake Passage. The water samples from the CTD/rosette system were collected into 100 ml glass ampoules and sealed off after a CFC free headspace of pure nitrogen had been applied. The CFC samples will be analysed in the CFC-laboratory at the IUP in Bremen. The determination of CFC concentration will be accomplished by purge and trap sample pre- treatment followed by gas chromatographic (GC) separation on a capillary column and electron capture detection (ECD). The amount of CFC degassing into the headspace will be accounted for during the measurement procedure in the lab. The system will be calibrated by analyzing several different volumes of a known standard gas. Additionally the blank of the system will be analyzed regularly. Furthermore, 480 samples from 41 stations were collected for helium isotopes (3 He, 4 He) and neon (Ne); 10 stations along the Greenwich meridian section, 14 stations along the Weddell Sea section, and 17 stations across the Drake Passage. The water samples from the water bottles were stored in clamped off copper tubes. They will be analysed with the IUP-Bremen noble gas mass spectrometer (combined quadrupole and sector field mass spectrometer), after the gases were extracted from the sea water samples and separated from other gaseous components by several cooling traps. Additionally, 50 samples from 6 stations (on the southern part of the Greenwich meridian section and above the northwestern slope along the Weddell Sea section) were collected for tritium (3H). The water samples were collected into water vapour tight glass bottles. Since tritium is part of the water molecule, all gasses will be extracted from the water sample, and the remaining water will be stored for at least half a year. During that time a sufficient part of the 3H has decayed to 3 He. Finally, the 3 He is measured with the same IUP- Bremen mass spectrometer as described above. Expected results Chlorofluorocarbons (CFC5) are gaseous, anthropogenic tracers that enter the ocean by gas exchange with the atmosphere. The evolution of these transient tracers in the ocean interior is determined by their temporal increase in the atmospheric and by the formation and mixing processes of intermediate, deep and bottom water. The total inventories of CFC5 in deep and bottom water reflect the accumulation of CFCs carried by its surface near source water masses. Together with the known atmospheric CFC evolution, CFC inventories allow, thus estimating the renewal or formation rates of recently formed bottom water. Furthermore, the availability of time series from various sections allow to assess the temporal variability of the formation rates, and possibly, its relation to changing environmental (boundary) conditions (ice shelf decay, surface water warming, etc.). Other methods using CFC5 as age tracers include transit time distributions (TTD5, or age spectra). By applying a "mean age", a "width of the age", and, if appropriate, a tracer free (i.e. "old") component, this dating method accounts for advection and mixing, other than the "CFC-ratio age" approach, which accounts - as a first approach - for advection and tracer free dilution only. This improves the estimates of ventilation time scales, mixing parameters, and ventilation or formation rates significantly. To constrain the parameters of the TTD well, it is valuable to use transient tracers from different observation times (e.g. CFC time series). Furthermore, the derived TTDs can be used to estimate the input, internal transfer, and storage of anthropogenic CO2. Using stable tracers like helium isotopes and neon, additional to temperature and salinity, allow one to carry out an Optimum Multiparameter (OMP) analysis to estimate the contributions of the parent source water masses to the formation of deep water masses. Herein helium and neon are ideal tracers to detect smallest fractions of glacial melt water or ISW, and the 3He/4He isotope ratio is a tracer for deep water from the Pacific (SPDSW). ANT XXIV/3 Data Report: CFC and noble gas measurements Oliver Huhn, Monika Rhein RV Polarstern, ANT XXIV/3 Cape Town - Prime Meridian, Weddell Sea - Punta Arenas 08. February - 16. April 2008 Chief Scientist: Eberhard Fahrbach Principle Investigator: Oliver Huhn, Monika Rhein Cruise participants: Oliver Huhn, Madlen Gebler, Alexandra Gronholz CFC measurements: Klaus Bulsiewicz Contact: Oliver Huhn Universität Bremen Institut für Umweltphysik (IUP) - Ozeanographie Institute of Environmental Physics (IUP) - Oceanography Otto-Hahn-Allee 1 D-28359 Bremen, Germany Tel.: +49 - 421 - 218 62155 FAX: +49 - 421 - 218 62165 Email: ohuhn@physik.uni-bremen.de Datafile (ascii): ANT-XXI4/3 2008-02-08-to-2008-04-16 Station Cast Bottle number Bottle depth Latitude Longitude CFC-11 [pmol/kg] CFC-11-Flag CFC-12 [pmol/kg] CFC-12-Flag The tracer data set was carefully checked for accurate measurements and outliers. According to the WOCE standards the following flags were applied to each measurement: flag 2 = good flag 3 = doubtful flag 4 = bad flag 6 = mean of replicates flag 9 = no measurement (then, the data value is set to -9.000) Methods During the cruise a total of 1620 samples on 97 CTD/water bottle stations were collected for chlorofluorocarbons (CFC-11 and CFC-12); 32 stations were occupied along the Greenwich Meridian section, 37 stations along the Weddell Sea section, and 28 stations across the Drake Passage. The water samples from the CTD/rosette system were collected into 100 ml glass ampoules and sealed off after a CFC free headspace of pure nitrogen had been applied. The CFC samples will be analysed in the CFC-laboratory at the IUP in Bremen. The determination of CFC concentration will be accomplished by purge and trap sample pre-treatment followed by gas chromatographic (GC) separation on a capillary column and electron capture detection (ECD). The amount of CFC degassing into the headspace will be accounted for during the measurement procedure in the lab. The system will be calibrated by analyzing several different volumes of a known standard gas. Additionally the blank of the system is analyzed regularly. Chlorofluorocarbons (CFC-11, CFC-12) The Chlorofluorocarbon (CFC-11 and CFC-12) water samples from the CTD-bottle- system are stored in glass ampoules without contact to the atmosphere during the tapping. Immediately after sampling the ampoules are flame sealed after a CFC free headspace of pure nitrogen had been applied. The loss of CFCs into the headspace is considered by a careful equilibration between liquid and gas phase under controlled conditions before the sealed ampoules are opened and a precise measurement of the volume of the headspace. The determination of CFC concentrations in the IUP Bremen gas chromatography lab is accomplished by purge and trap sample pre-treatment followed by gas chromatographic (GC) separation on a capillary column and electron capture detection (ECD). The system is calibrated by analyzing several different volumes of a known standard gas. CFC concentrations are calibrated on SIO98 scale (Prinn et al., 2000). A more detailed description of the measurement system is given by Bulsiewicz et at. (1998). Bulsiewicz, K., H. Rose, O. Klatt, A. Putzka, W. Roether (1998). A capillary- column chromatographic system for efficient chlorofluoromethane measurement in ocean waters. Journal of Geophysical Research, Vol. 103 (C8), 15959-15970, DOI: 10.1029/98JC00140. Prinn, R. G., R. F. Weiss, P. J. Fraser, P. G. Simmonds, D. M. Cunnold, F. N. Alyea, S. O'Doherty, P. Salameh, B. R. Miller, J. Huang, R. H. J. Wang, D. E. Hartley, C. Harth, L. P. Steele, G. Sturrock, P. M. Midgley, A. McCulloch (2000). A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE. Journal of Geophysical Research, Vol. 105, 17.751-17.792, DOI: 10.1029/2000JD900141. Accuracy (i.e. uncertainties of calibrated sample volume, calibration curve, extraction efficiency, standard and working gas, water blank, etc.): CFC-12 < 1.8 % CFC-11 < 2.8 % Precision (i.e. mean error from 19 replicate samples): CFC-12 < 0.007 pmol/kg or < 0.9% (which ever is greater) (n=6) We do not give a value for the precision of CFC-11. Offline sample chromatograms regularly show a negative peak in the vicinity of the CFC-11 peak, which decreases the accuracy of CFC-11 in comparison to CFC-12, and which does not allow giving an objective estimate of a precision for CFC-11. CFC-11 data between stations 140 and 193 (south of 61°S on the Prime Meridian and east of 28°W on the Weddell Sea section) are not reliable due to a possible hidden peak below the CFC-11 peak and possible problems with the measurement unit during that time (K. Bulsiewicz, personal communication, 2010). We flag these CFC-11 data generally as doubtful (3). Acknowledgment Sampling on board and measurement of CFCs and noble gases at the IUP Bremen was funded by the Deutsche Forschungsgemeinschaft within the SPP 1158 "Antarktisforschung", grant RH 25/32. We thank Eberhard Fahrbach, Gerd Rohard and the scientific party to participate in the ANT XXIV/3 expedition and for the excellent assistance and cooperation on board. We thank also master and crew of RV Polarstern. 2.5 OXYGEN MEASUREMENTS Ismael Nünez-Riboni(1), Hein de Baar(2), (1)Alfred-Wegener-Institut Marielle Lacombe(3), Charlotte Lohse(1), (2)NIOZ and Gerd Rohardt(1) (3)CNRS LEGOS Oxygen measurements from samples To calibrate the oxygen profiles measured with the optode sensor of both CTDs, from AWI and NIOZ, water samples of the Niskin bottles of both CTD5 were taken from station 97 to station 251. One sample of water was taken at the surface, one at the ocean bottom and one at the oxygen minimum. Additional samples were taken along the water column: one sample each thousand meters. In most of the cases, 5 or 6 water samples were taken from each cast. In shallow stations only 2 or 3 samples were taken. Every sixth CTD cast, replicas were taken (i.e., at least 15 % of the all the samples are replicas). In total, 651 samples were taken. The oxygen was measured using the Winkler method, according to the manual "WOCE operation and methods" (C.H. Culberson, July, 1991). Immediately after the sampling, the dissolved oxygen was fixed with 1 ml of MnCl2·4H2O and 1 ml of NaOH+Nal. Then, the bottles were stored under water and their caps were attached with a rubber band to prevent intrusion of air. To measure the dissolved oxygen, 1 ml of Sulphuric Acid 50% (H2504) was added to the samples and a solution of Sodium Thiosulfate (Na2S2O3·5H20) was titrated with a Dosimat Metrohm automatic pipette provided with a transmissiometer. Potassium iodate (KIO3) was used as standard. Preliminary results of these measurements show an accuracy of 0.028 ml l(-1) (based on the standard deviation of 22 replicas). While the AWI CTD sensor seems to be relatively stable (constant offset), the NIOZ CTD sensor drifted with time, measuring less oxygen every day, see Fig. 2.29. Due to problems with the Dosimat (failure of the device to measure some samples, bubbles in the pipette, etc.), the first half of the expedition (up to 10 March, i.e., station 163) results of the titration were not completely satisfactory: imprecise outcome of the titration resulted in a large dispersion of the offset around a straight line. After various attempts of improving the measuring process, on 10 March, the titer bottle and the pipette were changed; new titer was prepared, added to the bottle and standardized. After this, the titration results matched the CTD profiles along the vertical considerably better. Monitoring of the offset between CTD and titration results ruled the sampling frequency of each CTD, depending on the dispersion of the off- set around the straight line. Because of this, the first half of the expedition, samples were taken from every cast of both CTDs. After the offset seemed to be stable, and considering that the AWI CTD5 occurred with a large frequency, samples were taken only from one cast per day. Since casts of the NIOZ CTD occurred every second or third day, every cast of the NIOZ CTD has been sampled. Fig. 2.29: Oxygen difference between the measured samples and the reading from the CTD's oxygen sensor versus station number for the AWI and NIOZ system Three individual steps of correction were applied for the AWI CTD oxygen sensor: 1. Step: Linear correction of the CTD oxygen reading OXYl = a + b * OXY with: a = -0.02291300577 b = 1.029883905 2. Step: Linear correction of the oxygen sensor drifts ∆OXYl = a + b * Stationnumber with: a = -0.14125 b = 0.0008125 OXY2=OXYl+∆OXYl 3. Step: High order polynomial fit to correct the pressure effect of the oxygen sensor a: In upper water column; 0 to 2370 dbar: ∆OXY2 = a+b * PRES with: a = -0.04598245614 b = 2336842105E-005 and pressure given in decibar. b: In the deep water column; pressure > 2370 dbar: ∆OXY2 = a+b*PRES+c*PRES(^2)+d*PRES(^3)+e*PRES(^4)+f*PRES(^5)+g*PRES(^6) with: a = 0.01938375746 b = -0.0001436734808 c = 7.707321788E-008 d = 1.241336138E-011 e = -1.460247804E-014 f = 3.065354609E-018 g = -2.023542164E-022 and pressure given in decibar. The final corrected CTD oxygen reading is: OXY(corr) =OXY2+∆OXY2 The correction of the NIOZ CTD oxygen sensor was made for two separated parts due to the sensor drift which can be clearly identified in Fig. 2.29. Two individual steps of correction were applied for the first part from station number 97 to 178: 1. Step: Correction of the oxygen sensors pressure effect ∆OXYl = a + b*log(pressure) with: a = 0.5972460117 b = -005964890171 and pressure given in decibar. 2. Step: Linear correction of the oxygen sensor drifts ∆OXY2 = a + b * Stationnumber with: a = 0.242 b = -00019 The final corrected CTD oxygen reading for station 97 to 178 is: OXY(corr) = OXY+ ∆OXYl + ∆OXY2 The following correction was applied for the second part form station number 187 to 252: 1. Step: Linear correction of the oxygen sensor drifts ∆OXYl = a + b * Stationnumber with: a = 2.975 b = -0.01625 2. Step: High order polynomial fit to correct the pressure effect of the oxygen sensor ∆OXY2 = a+b*PRES+c*PRES(^2)+d*PRES(^3)+e*PRES(^4)+f*PRES(^5)+g*PRES(^6) with: a = -0.1744698393 b = 0.0007819713073 c = -8.445337449E-007 d = 3.882443376E-010 e = -9.007417652E-014 f = 1.034638749E-017 g = -4.679330148E-022 and pressure given in decibar. The final corrected CTD oxygen reading for station 187 to 252 is: OXY(corr) = OXY + ∆OXYl + ∆OXY2 Fig. 2.30 shows the remaining oxygen difference between the measured samples and the corrected reading from the CTD oxygen sensor. The sensor from the NIOZ CTD shows a little higher noise than the AWI CTD oxygen sensor which reflects the sensor problems which were already visible in the plot of the uncorrected data. The standard deviation for the AWI CTD is 0.04 and 0.07 for the NIOZ CTD. From there the accuracy for all CTD oxygen is better than ±0.1 ml/l. Fig. 2.30: Oxygen difference between the measured samples and the reading from the CTD's oxygen sensor after applied corrections versus station number for the AWI and NIOZ system. The oxygen profiles of the CTD were constantly compared with the results of the titration along the expedition. The profiles were roughly corrected by shifting them horizontally (adding or subtracting an offset) until they optimally matched the titration results by minimal quadratic differences (Fig. 2.31 shows station 244 as an example). Fig. 2.32 shows the offset between each CTD profile and the corresponding titration values against the station number. The authors of this report wrote also an succinct manual about oxygen sampling and measuring. This manual is available under request. Fig. 2.31: Comparison of the oxygen profile of the CTD sensor of Station 244 (black continuous line) and the titration values (stars). To monitor the results (and not as calibration procedure), the CTD profile has been shifted adding an offset until it matched by minimum quadratic differences the titration values (grey dashed line). Fig. 2.32: Offset between the CTD oxygen profiles and the titration results for the AWI CTD (red) and the NIOZ CTD (black) as a function of the station number. The offset is defined as the amount of oxygen added or subtracted to the profile as to match the titration values by minimum quadratic differences. 3. GEOTRACES IN THE INTERNATIONAL POLAR YEAR DURING ANT-XXIV/3 EXPEDITION General objectives One major aim of international GEOTRACES (http://www.geotraces.org) is: "To determine global ocean distributions of selected trace elements and isotopes, including their concentration, chemical speciation, and physical form, and to evaluate the sources, sinks, and internal cycling of these species to characterise more completely the physical, chemical and biological processes regulating their distributions". The International Polar Year (IPY) is an excellent opportunity to study Trace Elements and Isotopes in the Arctic and Antarctic Oceans. An international suite of vertical sections in the polar oceans is integrated in the IPY project No. 35 (http://www.ipy.org/development/eoi/proposal-details.php?id=35) entitled: "International Polar Year GEOTRACES: An international study of the biogeochemical cycles of Trace Elements and Isotopes in the Arctic and Southern Oceans". In context of this IPY-GEOTRACES, two Polarstern cruises have been implemented, in the Arctic Ocean (ARK-XXII/2; 2007) and the current expedition in the Antarctic Ocean (ANT-XXIV/3; 2008), respectively. Organization The GEOTRACES research of ANT-XXIV/3 pivots around three research teams of Royal NIOZ, IFM-GEOMAR and AWI led by Principal Investigators (PI) Hein de Baar, Peter Croot and Michiel Rutgers van der Loeff, respectively. Moreover there are several participants of other institutes CNRS-LEGOS, Stanford University and University of Groningen taking part in one or another of these teams. Data management All data of Isotopes and Trace Metals will be reported into the worldwide database of the GEOTRACES programme. Within the GEOTRACES Scientific Steering Committee, Dr. Reiner Schlitzer (AWI) is the SSC- member responsible for the database, and will be able to correspond regularly with the other SSC members Michiel Rutgers van der Loeff (AWI) and Hein de Baar (NIOZ) which had organized the ANT-XXIV/3 GEOTRACES component. 3.1 Trace elements during ANT-XXIV/3 expedition: NIOZ team Anne-Carlijn Alderkamp(3), Hein de Baar(1), (1)NIOZ Babette Bontes(2), Loes Gerringa(1), (2)University of Groningen Maarten Klunder(1), Patrick Laan(1), (3)Stanford University/ Rob Middag(1), Ika Neven(2), Sven Ober(1), University of Groningen Jan van Ooijen(†1), Willem Polman(1), Cornelis van Slooten(2), Charles-Edouard Thuroczy(1) In GEOTRACES we have defined 6 key trace metals (Tab. 3.1) which, together with additional metals Co, Ni, Ag will be investigated in IPY- GEOTRACES subprojects. The distribution and biological availability of Fe (3.1.1) is strongly controlled by its physical-chemical speciation (3.1.2) within seawater, where colloids and Fe-organic complexes are dominant actors. The external sources of Fe into the oceans are either from above (dust) and below (sediments) and will be constrained by Al and Mn (3.1.3) for aeolian dust input and sedimentary redox cycling sources, respectively. For phytoplankton growth, Cu (3.1.4) at the cell wall acts in reductive dissociation of Fe-organic complexes, hence facilitates Fe uptake. This may partly explain the nutrient-type distribution of Cu in the oceans. The Fe enhances phytoplankton growth, which in turn strongly controls the biological pump for uptake of CO2 from the atmosphere into polar oceans (4.). The increasing CO2 in polar ocean waters may affect phytoplankton ecophysiology (3.1.7), with key links of metals Fe (3.1.1) in the overall photosynthetic apparatus and Zn (3.1.4) in carbonic anhydrase and respectively, where Cd and Co (3.1.4) may substitute for Zn in the latter carbonic anhydrase. Tab. 3.1: The 6 trace metals with high priority in GEOTRACES. Many more trace metals are measured during GEOTRACES, yet these 6 were measured or sampled on all sections. Moreover Co, Ni, Ag of subproject 3.1.4. Fe Iron Most important essential micronutrient Al Aluminium Tracer of Fe inputs (from mineral dust and elsewhere) Zn Zinc Second important micronutrient; co-factor in carbonic anhydrase; toxic at high concentrations; environmental pollutant worldwide Mn Manganese Tracer of Fe inputs and redox cycling; Fe-Mn in superoxide dismutase Cd Cadmium Essential micronutrient; paleoproxy for phosphate in seawater; toxic at high concentrations; environmental pollutant worldwide Cu Copper Essential micronutrient (toxic at high concentrations); toxic at high concentrations; environmental pollutant worldwide Co Cobalt Essential micronutrient; co-factor vitamin 131 2 Ni Nickel Essential micronutrient; in urease Ag Silver Analog of both Cu and Si; paleoproxy for nutrient silicate; environmental pollutant 3.1.1 Distributions, sources, sinks of dissolved Fe in Polar Oceans Patrick Laan, Maarten Kiunder NIOZ Very little data exists on Fe in waters of the Antarctic Ocean. There is some data for Fe (or other trace metals) in surface waters of the Arctic Ocean, and very little at depths below ca. 1000 metres. Since the 1988 European Polarstern Study the role of Fe in ecology of the Southern Ocean has been investigated, including the Fe distributions, speciation, sources and sinks. Nevertheless in an exhaustive synthesis of all then existing ocean Fe data uncertainty remained as to the actual, correct, concentration of Fe in ocean waters. Therefore total dissolved Fe is a top priority in GEOTRACES. ANT-XXIV/3 aimed for two complete sections on distributions of Fe (and other trace metals) in the Antarctic Ocean. Work at sea Dissolved iron was measured directly on board by Flow Injection Analysis (FIA) after De Jong et al. 1998 in a cleanroom container. In a continuous FIA system the acidified pH 1.8, filtered (0.2 µm) seawater is buffered to pH 4.0. The iron is concentrated on a column which contains the column material aminodiacetid acid (IDA). This material binds only transition metals and not the interfering salts. After washing of the column with ultra pure water (MO) the column is eluted with diluted acid. After mixing with luminol, peroxide and ammonium the oxidation of Iuminal with peroxide is catalysed by iron and a blue light is produced and detected with a photon counter. The amount of iron is calculated using a standard calibration line, where a known amount of iron is added to low iron containing seawater. Using this calibration line a number of counts per nM iron is obtained. All 23 stations on the prime meridian and corresponding depths have been analyzed on board. The values of DFe measured varied from below 50 pM in the surface waters up to more then 2 nM. The standard deviation varied between 0% and 7% (exceptional), but was generally lower than 4%. The standard deviation of the values is determined of a triplicate measurement of the same sample bottle. To correct for contamination during the process or in the sample bottle a duplicate sample was taken of every station depth. The daily consistency of the system was verified using a drift standard. Regularly a certified SAFe standard (Johnson et al. 2007) for the long term consistency and absolute accuracy was measured. Next to the 23 stations also the amount of dissolved iron in the 1000 kDa filtered fraction was measured for 7 casts. The corresponding 02 pm filtered fraction of the same casts was also measured. The 1,000 kDa filtered fraction generally contained a lower amount of dissolved iron. Although all ultraclean CTD casts were sampled for the determination of dissolved iron on board only the samples from the prime meridian were measured. Due to the accident at Neumayer station we were not able to measure all the station taken and all the primaire goal was to finish the prime meridian. Preliminary results The preliminary data shown in Fig. 31, show that the concentrations of dissolved iron in South Atlantic Sector of the Southern Ocean are comparable to the concentrations found in the North Atlantic Deep Waters, 0.6 -0.7 nM. (Martin et al., 1993). Elevated DFe values were observed around 55°S and are most probably related to hydrothermal activity from the area where the Mid Atlantic, the Southwest Indian and the America-Antarctic Ridges meet. The lowest DFe concentrations were observed in the surface of the most southerly located stations. Fig. 3.2 shows a typical profile of the DFe as observed in the Southern Ocean. Fig. 3.1: Distribution of DFe on a section along the Greenwich meridian for Fig. 3.2: Depth profile of dissolved Iron References Johnson et al., 2007. Developing standards for dissolved iron in Seawater. Eos, Vol 88, n. 11. Martin J.H., Fitzwater, SE., Gordon, R.M., Hunter, C.N., and Tanner, S.J. (1993), Iron, primary production, and carbon- nitrogen flux studies during the JGOFS North Atlantic Bloom Experiment. Deep sea Research II. 40, 115-134. De Jong, JIM, den Das, J., Bathmann, U., Stoll, M. H.C., Kattner, G., Nolting, R.F., and de Baar, H.J.W. (1998). Dissolved iron at subnanomolar levels in the Southern Ocean as determined by shipboard analysis. Analytica Chimica Acta, 377, 113-124. 3.1.2 Physical and chemical speciation of iron in seawater Charles-Edouard Thuroczy and Loes Gerringa NIOZ Objectives The distribution and biological availability of Fe is strongly controlled by its physicalchemical speciation within seawater, where colloids and Fe-organic complexes are dominant factors. In order to study the distribution and the biological availability of Fe the natural Fe organic complexes over the whole water depth were determined in three different size fractions. Special attention was given that distinct water masses present were sampled as well. Samples were collected by an ultraclean sampling system using 24 Go Flo bottles fixed on an all-titanium frame and with a Kevlar cable. The concentration of iron binding ligands (organic compounds which strongly bind Fe) and their binding strength (conditional stability constant) are studied in 3 size classes here: unfiltered water, 0.2 µm filtered water and smaller than 1,000 KDa ultra-filtrated water. Methods General Under ultraclean conditions the 0.2 µm filtered seawater was ultra- filtrated using polyethylene hollow-fiber filters as to make an operational defined distinction between large colloidal and small colloidal Fe including the "truly dissolved" Fe (1,000 KDa nominal weight, Stereapore, Mitsubishi-rayon Co. Ltd, Nishioka and al., 2005). The dissolved organic iron (0.2 µm filtered) as well as the truly dissolved iron (< 1000 KDa) were analysed by Maarten Klunder and Patrick Laan using a chemo luminescence method (FIA) with acidified samples (pH 1.8). Total iron will be measured 6-12 months after the acidification of the unfiltered sample. The natural ligand characteristics were determined by doing a complexing ligand titration with addition of iron (between 0 and 8 nM of Fe added) in buffered seawater (mixed NH3/NH4OH borate buffer, 5 mM). The competing ligand 'TAC' (2-(2-Thiazolylazo)-pcresol) with a final concentration of 10 µM was used and the complex (TAC)2-Fe was measured after equilibration (> 15 h) by cathodic stripping voltammetry (CSV) (Croot and Johansson, 2000). The electrical signal recorded with this method (nA) was converted as a concentration (nM), then the ligand concentration and the binding strength were estimated using the non-linear regression of the Langmuir isotherm (Gerringa and al., 1995). The voltammetric equipment consisted of a µAutolab potentiostat (Type I, II and III, Ecochemie, The Netherlands), a mercury drop electrode (model VA 663 from Metrohm). All equipment was protected against electrical noise by a current filter (Fortress 750, Best Power). Extra experiment Instability with time of the unfiltered seawater was observed during the ARK-XXII/2 cruise in 2007 and made the estimation of the ligand characteristics difficult. This raised the question how long samples could be kept before analysis ("expiration") because life (algae, bacteria, viruses) modified the equilibrium in the sample. Three experiments were performed in order to establish the "expiration date" of the unfiltered seawater samples. These experiments want to explain what causes the perturbations in the samples. For this, four size fractions were analysed after different conditions of conservation (temperature and light). The four fractions were unfiltered water, 1 pm filtered water (without the big algae), 02 µm filtered water (without the pico-eucaryotes) and 1,000 KDa filtered water. With the collaboration of Claire Evans and Erwin Frijling, the total chlorophyll fluorescence of the algae was measured by Phyto-PAM (Pulse Amplitude Modulation) and followed in time (between 5 and 10 days), as well as the amount of living small algae (pico-eucaryotes) measured by flow-cytometry. Samples for bacteria analyses were also taken and will be analysed at NIOZ. The dissolved iron concentration was measured by FIA and the ligand concentrations and binding strength were measured on board by voltammetry. Another experiment was performed in order to establish a mass balance of the ligands before and after the ultrafiltration. Four classes of size were then analyzed, the unfiltered fraction, the 0.2 µm filtered fraction the 1,000 KDa ultrafiltered fraction, but also the fraction left after the ultrafiltration (size between 0.2 µm and 1,000 KDa). Sampling statistics Seven stations were sampled on the Greenwich meridian transect with a maximal depth of 4,500 m. A total of 140 samples on 56 depths were sampled (28 of unfiltered, 56 of 02 µm filtered and 56 of 1,000 KDa ultra-filtered). Among them, 11 depths characterizing the most important water-masses were sampled twice and kept frozen for later analyses while back at NIOZ (for the study of kinetic exchange between the different forms of iron). Two profiles were sampled in the Weddell Sea for a total of 46 samples (8 of unfiltered, 19 of 0.2 µm filtered and 19 of 1000 KDa ultra- filtered). 8 depths were also sampled twice to characterize important water-masses. Two other depths were also taken on a third station to start the mass balance experiment. In the Drake Passage one station was sampled for a total of 30 samples (10 depths). A second station was used to continue the masse balance experiment. Preliminary results Only results of the fraction smaller than 0.2 µm could be calculated at the time of this report. The following figures (33, 3.4 and 3.5) show the vertical profiles of iron and of the ligands in the fraction smaller than 0.2 µm. These 3 profiles are 3 stations along the Greenwich meridian. The concentration of the ligand is expressed in nanoequivalents of mol Fe (nEq of MFe), meaning sites present at the ligand molecules at which Fe can be bound in such a way as described by the determined binding strength (conditional stability constant). The conditional stability constant ranged from 10(^21.87) to 10(^23.35), and a mean value of 10(^22.44). The excess ligand concentration is calculated by subtracting the dissolved Fe concentration from total ligand concentration, resulting in the concentration of empty ligand sites (not filled with Fe) of the sample. In all samples, except one, the excess ligand concentration was larger than zero, implicating that more than 99% of the dissolved Fe was bound to the ligands. It is possible that the sample in station 107 at 2,500 m depth (Fig. 3.5) was contaminated with Fe. The results of the extra experiments indicate that unfiltered samples stored correctly (4°C) can be kept for 1 or 2 days before changes occur. However, as soon as the algae die, changes occur in the ligand concentration as well as in the binding strength of the ligand. Fig. 3.3: Station PS 71-101/2, concentration of iron and ligands with the depth Fig. 3.4: Station PS 71-103/1, concentration of iron and ligands with the depth Fig. 3.5: Station PS 71-107/3, concentration of iron and ligands with the depth References Croot P.L., Johansson M. (2000). Determination of iron speciation by cathodic stripping voltammetry in seawater using the competing ligand 2-(2-Thiazolylazo)-p-cresol (TAC). Electroanalysis. 12, No.8, 565-576. Nishioka J., Takeda S., de Baar H.J.W., Croot P.L., Boye M., Laan P., Timmermans K.R. (2005). Changes in the concentration of iron in the different size fractions during an iron enrichment experiment in the open Southern Ocean. Marine Chemistry. 95, 51-63. Gerringa, L.J.A., P.M.J. Herman, T.C.W. Poortvliet (1995). Comparison of the linear Van den Berg/Ruzic transformation and a non-linear fit of the Langmuir isotherm applied to Cu speciation data in the estuarine environment. Marine Chemistry. 48, 131-142. 3.1.3 Dissolved Al and Mn as source tracers for iron Rob Middag and Cornelis van Slooten NIOZ Objectives For the world oceans, the initial hypothesis of Fe coming from above has been challenged by upwelling supply from below where reducing marine sediments are the ultimate Fe source. Dissolved Al in surface waters is a tracer of aeolian dust input and indeed very high in the Mediterranean where dissolved Fe is also high due to dust supply from the adjacent Sahara and Egypt arid regions. The dissolved Al and dissolved Fe also co-vary on a transect from the Canary Basin to Gibraltar. Data of Al is scarce in polar seas, and IPY GEOTRACES aims to fill this gap for better assessment of dust input. Elevated dissolved Mn and Fe in reducing environments render dissolved Mn a source tracer for Fe from below, i.e. from reducing sediments. Our combined Mn-Fe data, also with natural radiotracers will quantify the Fe from below source. Work at sea Dissolved Al and dissolved Mn were measured directly using shipboard FIA measurements. In a continuous FIA system, the acidified pH 1.8, filtered (0.2 µm) seawater is buffered to pH 5.5 and 85 for Al and Mn, respectively. The metals are concentrated on a column which contains the column material aminodiacetid acid (IDA). This material binds only transition metals and not the interfering salts. After washing of the column with ultra pure water (MO) the column is eluted with diluted acid. The Al is determined using lumogallion after Brown and Bruland (2008). Lumogallion is a fluorometric agent and reacts with aluminium. The change in the fluorescence detected by a fluorometer is used as a measure for the dissolved Al concentration. In order to verify the consistency of the analysis, every day a sample was measured from a 25 liter tank that was filled in the beginning of the cruise. Also a duplicate sample was taken every cast and this sample was analysed with the samples of the next cast to further check for inter daily variation. Furthermore, SAFe seawater samples were analysed daily and the values are consistent with those found by Brown and Bruland (2008). The Mn is detected using the chemoluminescence method of Doi et al. (2004). The oxidation of luminol by hydrogen peroxide produces a blue light. This oxidation reaction is catalyzed by manganese and the increase in the production of blue light is detected by a photon counter and used as a measure for the dissolved Mn concentration. Also for Mn similar consistency checks as for Al have been performed with samples from the 25 liter tank and duplicate samples. Also SAFe seawater was analysed which was consistent with the values found previously in the lab and by Mendez (pers. com). The daily consistency of the system was verified using a so-called drift standard. Preliminary results The preliminary data shows that the values in the surface for dissolved aluminium are low over the Greenwich meridian (Figs. 3.6 and 3.7). The increase of Al with depth as observed in the Arctic and North Atlantic oceans is far less profound in the Southern Ocean. Higher deep values of up to 6 nM were found closest to the African continent while close to the Antarctic continent the deep values where below 2 nM. The section over the Greenwich meridian consisted of 22 stations and a total of 486 samples were analysed for dissolved Al over the Greenwich meridian. Another 8 stations were sampled in the Weddell Sea and 10 more in the Drake Passage bringing the total number of samples to 915. The Weddell Sea bottom water appears to be somewhat enriched in dissolved Al and some elevated values were found just under the surface going into the Drake Passage. The Mn values are quite low throughout the water column (Figs. 3.8 and 3.9), except for areas with suspected hydrothermal input enriching the deep waters with Mn. Going from deep to surface the Mn values start to increase towards the surface as is generally observed for Mn, but the values drop sharply in the last 25 to 50 metres indicating a depleted surface layer. The section over the Greenwich meridian consisted of 22 stations and a total of 496 samples were analysed for dissolved Mn. Another 8 stations were sampled in the Weddell Sea and 10 more in the Drake Passage bringing the total number of samples to 926. These sections showed Mn input from the Peninsula and Antarctic islands. Fig. 3.6: Distribution of dissolved Al on a section along the Greenwich meridian Fig. 3.7: DAI profile station 167 Greenwich meridian Fig. 3.8: Distribution of dissolved Mn on a section along the Greenwich meridian Fig. 3.9: DMn profile station 167 Greenwich meridian References Doi, T., Obata, H., Maruo, M., 2004. Shipboard analysis of picomolar levels of manganese in seawater by chelating resin concentration and chemiluminescence detection. Analytical Bioanalytical Chemistry 378 (5), 1288-1293. Brown, MT., Bruland, K.W., 2008. An improved flow-injection analysis method for the determination of dissolved aluminum in seawater. Limnology and Oceanography Methods 6,87-95. 3.1.4 Involvement of Co, Ni, Cu, Zn, Ag, Cd in biological cycles in Polar Oceans Patrick Laan, NIOZ not on board: E. Achterberg, NOC Objectives The first row of transition metals (Mn, Fe, Co, Ni, Cu, Zn) are essential for every living cell, in the sea and on land. Co is co- factor in vitamin B12, which most phytoplankton cannot synthesize hence needs to be provided in ocean waters. Zinc is in carbonic anhydrase for CO2 fixation by algae. Substitution of cobalt Co or cadmium Cd in carbonic anhydrase may occur under Zn deficiency stress. Also a specific Cd-based carbonic anhydrase exists in a certain diatom. These enzyme functions may partly explain the co-variance in the oceans of Zn with silicate (see 3.1.5), and Cd with phosphate. Also nickel Ni co-varies with both phosphate and silicate, and copper Cu resembles silicate, albeit less due to deep ocean Cu removal (akin to deep ocean Fe removal, see 3.1.2). The second row metal silver (Ag), despite having no biological function, also correlates with silicate. The thus far small (Cd, Ni, Cu) or very small (Zn, Ag) ocean data sets suggest interaction of Zn and Ag with the diatoms-and-Si cycle, and all (Ni, Cu, Zn, Ag, Cd) with the general ocean carbon cycle. The parallel measurements of nutrients (nitrate, phosphate, silicate) and alkalinity allows our study of metal-nutrient co-variances. With regards to the trace metals Cd, Cu, Ni and Zn this allows synergy and internal consistency with the project of Dr. Peter Croot (lfM-GEOMAR). Work at sea At each ultraclean station cast sample bottles of one litre each were filled with filtered seawater for measurements afterwards in the home laboratory of Co, Ni, Cu, Zn, Cd as well as dissolved Fe. Latter dissolved Fe as a duplication hence confirmation/verification of the direct shipboard detection. The home laboratory measurement of this suite of trace metals will be done by High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) with preceding in-line column preconcentration of the metal elements from seawater. Another set of small 60 ml bottles was collected and stored for measurements afterwards of dissolved silver Ag in the laboratory of collaborator Dr. Eric Achterberg, National Oceanography Centre, Southampton, UK. Expected results Within two years we hope to have analysed in all samples the first row of transition metals. With these results we hope to get a better understanding of the trace metal distributions throughout the world oceans and especially in the "High Nutrient Low Chlorophyll" region of the Southern Ocean. 3.1.5 Fractionations of the stable isotopes of cadmium Patrick Laan, Rob Middag, Cornelis van Slooten, Charles-Edouard Thuroczy, Hein de Baar, NIOZ not on board: Wafa Abouchami (MPI Chemie, Mainz), Mark Rehkamper (DESE, London) Objectives Within the oceans the trace metal cadmium (Cd) exhibits a close correlation with the nutrient phosphate. This suggests an involvement of Cd in the ocean biological cycle. This in turn has been suggested to serve as a paleoceanographic indicator of past concentrations of phosphate in the oceans. Here the elemental ratio of cadmium versus calcium (Cd/Ca ratio) in the calciumcarbonate of microfossils, notably foraminifera, would serve as a proxy tracer for paleo-phosphate. One implicit assumption of this paleo-application is that the Cd/PO4 proportions in seawater do not change significantly when the ocean changes, for example from a glacial period ocean into an interglacial period ocean. The involvement of Cd in the ocean biological cycle (de Baar et al., 1994; Loscher et al., 1998) may be due to two different processes. On the one hand Cd may have true biological uptake in plankton, and a true biological function inside the living cell. Until recently Cd was deemed to have no biological functionality. However now there is evidence of Cd sometimes serving as substitute for zinc (Zn) in the enzyme carbonic anhydrase. Moreover there is another line of evidence suggesting a truly Cd-based carbonic anhydrase enzyme in some diatoms. On the other hand Cd may become adsorbed by, in principle abiotic, chemical processes, on the outside of plankton material. When this plankton becomes debris and settles into the deep oceans where it is remineralized by bacterial consumption, the Cd may be released again and return into seawater solution in the deep sea. In general a true involvement in biological processes implies involvement in a large sequence of many biochemical reactions. Each reaction giving rise to slight mass fractionation, heavier isotopes tend to be left behind somewhat. The overall suite of many biochemical reactions will give rise to a significant, detectable, isotopic fractionation. This is well known for isotopes of biological elements carbon (C) and nitrogen (N). Similarly a significant isotopic fractionation of Cd isotopes in marine biota would cause major variation of the Cd isotope signal in the seawater from which the biota had derived its Cd. Therefore the Cd isotope ratio in various water masses will serve to indicate whether or not Cd is truly involved in biochemical processes. Moreover once Cd isotope ratio values can indeed be measured accurately in seawater, this will also serve as a tool for enhancing our understanding of the use of Cd as a paleo-indicator of phosphate. Work at sea Samples of seawater were collected both with the ultraclean CTD system for vertical profiles and with the clean torpedo and pumpline system for underway surface waters. Both type of samples were filtered over 0.2 micron nominal size cutoff filter cartridges and collected into pre-cleaned bottles. Sample volumes ranged from 1 L for deep waters (where Cd concentrations are deemed to be high), to 5 L in intermediate waters, 10 L in upper water column, and 20 L for water collected from 35 m depth with the torpedo. At the Greenwich meridian we obtained four vertical profiles of 8-10 sampling depths each at stations and hydrocasts PS71-104-2, PS71-113-2, PS71-138-2 and PS71-163-1 as well as 25 underway samples of 20 L each with the IFISH torpedo. In the Weddell Sea two vertical profiles were obtained at stations and hydrocasts PS71-198-2 and PS71-216-4, due to sea ice cover it was impossible to sample with the torpedo. In Drake Passage one vertical profile was obtained at station and hydrocast PS71-249-3 and one underway sample of 20 L with the IFISH torpedo. See the corresponding hydrocast sheets of A1. Ultraclean CTD for depths etc. of the vertical profile samples, and the Zero & Drake folder H. Iron Fish Cd Isotopes for fact sheets of the 26 underway surface samples with positions, S, T, and nutrients values. References De Baar, H.J.W., Saager, P.M. Nolting, R.F. ' Van der Meer, J. (1994) Cadmium versus Phosphate in the World Ocean. Mar. Chem., 46: 261-281. Löscher, B.M., J.T.M. de Jong and H.J.W. de Baar (1998) The distribution and preferential biological uptake of cadmium at 6°W in the Southern Ocean. Marine Chemistry, 62, 259286. 3.1.6 Trace metal input by aerosols Maarten Klunder, Charles-Edouard Thuroczy and Rob Middag NIOZ not on board: Alex Baker, University of East Anglia Objectives The input of airblown dust particles (aerosols) into surface waters is known to be a source of trace metals in seawater. In order to be able to quantify this source an aerosol collector from Dr Alex Baker (University of East Anglia) was placed on top of Polarstern's Peildeck. Shipboard collection of the aerosols was done by Maarten Klunder, Charles-Edouard Thuroczy and Rob Middag. Dr. Alex Baker will analyse the aerosols for trace metals in his laboratory. There is a close link with 3.1.3 where distributions of Al in surface waters are determined as independent tracer for aerosol input. Work at sea Every 50 to 72 hours a new filter was placed in the aerosol collector, depending on daylight and weather conditions. Unfortunately some sampling days were lost due to breaking down of the engine of the aerosol collector which had to be replaced. In total 21 filters were collected. The filters stayed on Polarstern till Bremerhaven in the -20°C freezer room. 3.1.7 Dynalife: Dynamic light conditions and iron limitation Anne-Carlijn Alderkamp University of Groningen, Stanford University not on board: Kevin R. Arrigo, Stanford University Objectives The DYNALIFE project is funded by the US-IPY programme and focuses on the interactions between DYNAmic light conditions and Fe limitation experienced by Antarctic phytoplankton. In addition to the availability of iron, light plays a major role in defining where and when the different phytoplankton taxa bloom. The light climate phytoplankton experience can be highly dynamic, as a result of diel cycles, changes in cloud cover and wind driven mixing of the upper layer of the ocean. These alternations between low and high light require regulation and acclimation of light harvesting, photosynthesis, and photoprotective pigments in the phytoplankton. In response to low light algae maximize their light harvesting capacity and photosynthetic efficiency. Yet, high light may cause damage to the photosystems leading to photoinhibition and therefore requires synthesis of protective pigments. Southern Ocean ecosystem model results indicate taxon- specific differences in photoinhibition may be a key factor in determining the distribution of a taxon. And, indeed, experiments with Antarctic phytoplankton in the laboratory have identified taxon- specific differences in photoacclimation and photoinhibition at different light conditions that contribute to explaining the observed distribution. In addition, iron (Fe) limitation of the algal communities in the Southern Ocean is now well documented, and directly affects the quantity and efficiency of the photosystems. Thus, Felimitation directly affects photoaccl imation and photoinhibition. The objective of the ANT-XXIV/3 cruise is to determine 1) if Antarctic phytoplankton experience photoinhibition when residing near te surface, 2) if photoinhibition is related to the depth of the mixed layer, and 3) the importance of repair of photodamage versus photoprotection. Work at sea To assess the ratio of photoprotective and light harvesting pigments, at 10 stations on the Greenwich meridian and 5 stations on the Weddell Sea transect, samples from the upper 100 m of the water column were filtered onto GF/F filters under low vacuum pressure, in-situ temperature and low light levels. Filters were snap-frozen in liquid nitrogen and stored at -80°C for pigment analysis by HPLC at the University of Groningen. To assess the extent of photoinhibition Antarctic phytoplankton receive when residing near the surface, short-term deck incubations were carried out at 9 stations on the meridian of Greenwich, 8 stations on the Weddell Sea and 5 stations on the Drake Passage transect. The depth of the mixed layer was determined based on the CTD profile. Samples containing in-situ phytoplankton were collected from surface water and the chlorophyll maximum. Subsamples were fixed for microscopic analysis of phytoplankton species and samples were filtered and stored at -80°C for analysis of photosynthetic and -protective pigments as described above. The photosynthetic efficiency of phytoplankton (Fv/Fm) was analyzed with a PAM fluorometer. Samples were incubated for 20 mins at incident light levels in deck incubators. The effect on the photosynthetic efficiency was determined by PAM fluorometer and subsequently, recovery of photosynthetic efficiency was measured during incubation at in-situ temperatures and low light levels. In parallel experiments the repair of photodamage was prevented by addition of the inhibitor lincomycin. Lincomycin inhibits transcription of chloroplast encoded proteins, such as the Dl protein, which is a crucial component of photosystem II and one of the first proteins to become damaged by high light. Preliminary data Significant photoinhibition was observed as a decrease in efficiency of photosynthesis (Fv/Fm) after incubating in-situ phytoplankton samples in deck incubators at incident light levels (see Fig. 3.10 for a typical example), both for samples from the surface as well as the chlorophyll maximum. Part of the decrease in photosynthetic efficiency was reversible during 120 mins of recovery under low light conditions. The inhibition of repair by the addition of lincomycin did not affect the decrease in photosynthetic efficiency during the in-situ incubation, but reduced the recovery in almost all experiments. Experiments conducted early in the morning, or at low incident light levels showed the least photoinhibition, which was rapidly reversed. Experiments conducted at higher light levels showed strong photoinhibition, that was not (completely) reversed during 120 mins of recovery. In these cases, lincomycin prevented recovery completely, as shown in Fig. 3.10. Fig. 3.10: A typical example of photosynthetic efficiency (Fv/Fm) dynamics during a deck incubation followed by recovery under low light conditions. Means and standard deviations are shown for triplicate incubations of water collected at 10 m and 50 m depth, without and with (+) the addition of lincomycin, an inhibitor of repair of photosystem II. Future work The characteristics of photoinhibition and recovery observed during incubation experiments will be related to species composition (microscopy), the ratio of photosynthetic and -protective pigments (HPLC analysis, University of Groningen), the characteristics of the mixed layer and the incident irradiance in the experiments. 3.1.8 Southern Ocean primary productivity in a high-CO2 world Babette Bontes(1), Ika Neven(1), (1)University of Groningen Stevenvan Heuven(1), Hans SIagter(1), (2)NIOZ Jan van Ooijen(2) Objectives Since the beginning of the Anthropocene, atmospheric CO2 levels have risen from 280 ppm to 370 ppm. This is higher than any CO2 concentration experienced on Earth in at least 400,000 years and a further increase up to 750 ppm by the year 2050 becomes increasingly inevitable. Along with rising atmospheric CO2 comes a continuing invasion of CO2 into the world oceans (particularly in polar areas), which is predicted to cause a drop of pH by 03 - 0.4 units. As a result only half of the preindustrial carbonate ion concentration [C032] might remain (Feely et al. 2004). With the biological pump overriding CO2 outgassing from upwelling deep waters, the Southern Ocean is an important sink for anthropogenic CO2. Thus, making the local phytoplankton community an important player within the global climate system. Surface ocean pH and CO2 changes in turn might have large impact on representatives of the major bloom forming taxonomic classes: diatoms, nanoflagellates, and haptophytes (mainly Phaeocystis antarctica) in the Antarctic Ocean proper (>50°S), and coccolithophorids in the sub- Antarctic region (<50°S) of the Southern Ocean. We are going to study the effects of different pCO2 in Southern Ocean seawater on the growth, vitality and carbon metabolism of the in-situ algal community. Work at sea CO2 manipulation experiments Five CO2 manipulation experiments were conducted. The first examined the influence of CO2 under Fe limited and Fe replete conditions; in the following experiments, CO2 was alternated only under Fe replete conditions. Seawater inoculums were collected from the chlorophyll maximum by the NIOZ ultraclean CTD and incubated in 10 L Polycarbonate carboys (Nalgene) at ambient temperature under 50 µEinstein m(^2)s(^-1) 16h: 8h light: dark cycle in a laboratory container. The following CO2 scenarios were mimicked in a semi-continuous set-up and monitored for 10 days - 190 ppm (Last Glacial Maximum) - 370 ppm (Present) - 750 ppm (Future 2050 A.D) Phytoplankton were daily enumerated and identified using flow cytometry, for species smaller than 20 pm, and microscope counts for large species. Algal viability and photosystem II (PS II) efficiency was measured daily on dark-adapted samples by the PhytoPAM fluorometer. In addition, nutrient dynamics have been monitored every day. On TO, T 5 days, T 7 days and T 10 days samples were collected for Fe, determination of particulate organic carbon (POC), dissolved organic carbon (DOC) and pigment composition. Dissolved organic carbon (DIC) and total alkalinity were monitored every other day throughout the experiments with methods described in sections 3.4.1 and 4.1. of this report. Short-term 14CO2/H14C03 disequilibrium experiments (Elzenga et al. 2000) were carried out on TO, 1 5 days and 1 10 days of the experiments to measure the extent external carbonic anhydrase (eCA), an enzyme which catalyses the dehydration of bicarbonate (HC03) to CO2 and vice versa in the boundary layer of phytoplanktonic cells, contributes to the uptake of inorganic carbon. In this way it was possible to distinguish between the inorganic carbon species taken up by cells. Transect To estimate the extent of bicarbonate uptake and the role of eCA in inorganic carbon uptake of Southern Ocean phytoplankton, short-term 14CO2/H14C03 disequilibrium experiments were carried out. In total 9 stations were assessed on the Greenwich meridian transect, 10 on the Weddell Sea transect and 6 on the Drake Passage transect. Preliminary results Measurements of DIC revealed that it took approximately 2 days of continuous aeration to reach the required levels of pCO2 in the experimental vessels. Subsequently the pCO2 remained reasonably stable during the experiment (data not shown). Fluorescence parameters, growth (Fig. 3.11), viability and photosynthetic efficiency (Fig. 3.12) were not affected by the different CO2 or Fe treatments. The dynamics of phosphate, silicate and nitrate (Fig. 3.13) suggest that neither Fe addition nor differences in CO2 concentration affected the nutrient uptake rates of the algae. 14C disequilibrium experiments revealed that communities cultured under 190 ppm make extensive use of the bicarbonate pool by eCA-mediated conversion to CO2This distinct pattern decreased under present CO2 conditions and ceased totally under future high CO2 conditions. Differences were already visible after the short incubation time of 5 days (Fig. 3.14). After analysis of pigment composition, POC and microscope samples a quantitative approach will be possible. In consistence with the experimental data, preliminary results of the Greenwich meridian and Weddell Sea transect suggest that the majority of phytoplankton makes only modest use of the bicarbonate pool under present CO2 conditions. The existence of a Carbon Concentrating Mechanism such as eCA that is quickly induced under low CO2 conditions implies that the majority of phytoplankton is well adapted to changing CO2 conditions. External CA- mediated conversion of bicarbonate to CO2 may have been beneficial in the past during changes in CO2 concentrations over geological timescales as well as during fast occurring CO2 shifts, for example during a phytoplankton bloom. However, under future high CO2 scenarios this once evolutionary advantageous trait might become redundant. Fig. 3.11: Phytoplanktonic growth during experiment 1 Fig. 3.12: Photosynthetic efficiency of phytoplankton during experiment 1 Fig. 3.13: Dynamics of nitrate, phosphate and silicate during experiment 1 Fig. 3.14: Differences in bicarbonate utilization by the in-situ phytoplankton community cultured for 5 days under different pCO2 conditions (l9Oppm, 38Oppm, 75Oppm) References Elzenga, J.T.M., Prins, H.B.A. and Stefels, J. (2000). The role of extracellular carbonic anhydrase activity in inorganic carbon utilization of Phaeocystis globosa (Prymnesiophyceae): a comparison with other marine algae using the Isotopic Disequilibrium Technique. Limnology and Oceanography. 45: 372 - 380. Feely, R.A., Sabine, C.L., Lee, K., Berelson, W., Kleypas, J., Fabry, V.J. and Millero, F.J. (2004). Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science. 305: 362-366. 3.1.9 Ultraclean CTD and sampling system Sven Ober(1), Willem Polman(1) (1)NIOZ (deceased 2 March 2008), Mihael Stimac(2) (2)Heli Service This CTD and sampling system was operated by Sven Ober (CTD operator and electronics) and Willem Polman (winch operator and overall mechanics). Due to the tragic loss of Willem Polman, the kind offer of Michael Stimac to continue as winch operator was gratefully accepted. This and the much appreciated extra support of the shipboard CTD team allowed the system to be operational again from 9 March onwards. During the cruise a special CTD system was used to sample for trace elements and isotopes. This CTD system consists of 3 major modules: a winch with a super-aramide CTD cable, a box-shaped titanium CTD frame and a clean air container that is designed to hold the CTD frame in order to enable subsampling and filtration under clean air conditions. The CTD frame is made of pure titanium and was equipped with a Seabird SBE9+ CTD underwater unit, a double SBE3/SBE4 temperatureconductivity-sensor set each with a separate SBE5 underwater pump, an SBE43 DOsensor, a Chelsea MK-111 fluorometer, a Seapoint OBS and a special sampling system. This sampling-system consists of a Multivalve hydraulic multiplexer and 24 GoFlo sampling bottles each with its own hydraulic release unit. (De Baar et al, 2007 and Ober et al, 2002). The temperature sensors were in-situ calibrated with an SBE35 reference thermometer. Salinity samples were analysed using an Guildline Autosal 8400B for the calibration of the conductivity sensors (See 211). The pressure sensor, mounted inside the SBE9+, was monitored using Electronic Reversing Pressure Meters, (Brand SIS, type 6000X). Winkler titrations were carried out in order to calibrate the SBE43 DO-sensor. In total 56 casts were carried out with the Ultraclean CTD system (Type Al: 41, type B2: 7, type D: 2, type G: 5, type F: 1) including an intercalibration cast with the CTD system operated by AWL This cast proved that both systems had a sufficient level of data quality enabling interchangeability during the cruise. Throughout the whole cruise the system worked very reliably, although some technical problems occurred. The primary conductivity sensor had to be exchanged after station 135, cast 1 for a spare because of erratic behavior due to a broken cell and the secondary sensor pair showed for still unknown reasons a noisy signal. The DO-sensor showed some drift in time and some depth dependency. As part of the processing of the CTD all available pre-cruise, post- cruise and in-situ calibration data were used to correct for the sensor imperfections. The way how the calibration values are obtained and processed are described in detail in chapter 2.1.1 of this report. Overall the data quality of the salinity is better than +1- 0002 and for temperature better than ± 0.001 K. The accuracy of the CTD oxygen is better than ± 01 ml/l. The hydraulic bottle control system worked perfectly (100%) and the GoFlo samplers worked very well (better than 99%). The analysis of dissolved Fe and dissolved Al showed very low concentrations in the surface water. The concentrations of dissolved Mn were very low at depth. These low concentrations proved that the sampling system did not contaminate the samples. The status of "Ultraclean" was confirmed conclusively. References De Baar, H.J.W., K.R. Timmermans, P. Laan, H.H. De Porto, S. Ober, J.J. Blom, M.C. Bakker, J. Schilling, G. Sarthau, M.G. Smit and M. Klunder (2008) Titan: A new facility for ultraclean sampling of trace elements and isotopes in the deep oceans in the international Geotraces program, Marine Chemistry, 111, 4-21. Ober, S., Groenewegen, R.L., Boekel, H.J., Keijzer, E.J.H., Derksen, J.D.J., Laan, M., 2002. A new way of oceanographic watersampling. Abstract of presentation at Inmartech, 8 October 2002, Yokusuku, Japan. http ://www.jamstec.go.jp/jamstec-e/whatsnew/inmartech2002/program.pdf. 3.1.10 Ultraclean sub-sampling and filtrations Patrick Laan(1), Maarten Klunder(1), (1)NIOZ Rob Middag(1), Cees van Slooten(1), (2)IFM-GEOMAR Charles-Edouard Thuroczy(1), Oliver Baars(2) Upon the evacuation of Maarten Klunder from Neumayer station, Oliver Baars kindly joined the team during the remaining period of subsampling from 9 March onwards to the end of the expedition. Once the ultraclean frame with 24 GOFLO samplers was placed inside the clean laboratory van an extensive programme of sub-sampling and filtrations was done, typically lasting 3 - 4 hours. Unfiltered seawater samples have been collected into various pre- cleaned bottles for the projects 3.1.8, 3.2.5, 3.3.6 (Barium only), 34.1, 5.1, as well as by the respective analists themselves for projects 25 and 4.1. Filtrations have been done with a 0.2tm Sartorius Sartobran 300 cartridge filter for the projects 3.1.1, 3.1.2, 3.1.3, 3.1.4, 3.1.5; 321, 322, 3.2.3; 3.3.6 (Rare Earths only) and 3.3.7. Moreover filtrations have been done for project 3.3.7 in another approach over a suite of two filter membranes of 5 micron and 0.45 micron nominal size cutoff respectively, placed in-line such that the first 5 micron filter takes out the larger size class marine particles, and next the finer 0.45 micron filter removes the smaller size class particles. In this manner not only the filtered seawater is collected, but also the filters for later analysis of the particles on the filters. 3.2 Trace elements during ANT-XXIV/3 expedition: IFM-GEOMAR team Peter Croot(1) and Rob SherreII(2) (1)IfM-GEOMAR (2)Rutgers University Background and general objectives In the High Nutrient Low Chlorophyll waters of the Southern Ocean the supply of iron controls primary productivity and thus the cycling of other key bio-elements (Co, Ni, Cd and Zn). While recent work has focused on the role of iron, it is now clear, mostly through at sea incubation experiments and laboratory studies, that other elements may also play a role in controlling the species composition of the phytoplankton and importantly the rates at which macronutrients are consumed by phytoplankton. These changes in rates of uptake are then reflected as differences in the nutrient ratios, or metal to nutrient ratios, of the phytoplankton themselves. A further complicating factor is that the chemical speciation and bioavailability of these bio- elements may also undergo changes as a function of phytoplankton growth fuelled by the supply of iron. Understanding of these processes is then critical for investigations into primary productivity of the Southern Ocean and the sources and sinks for major nutrients. Unfortunately at the present time there have been only a limited number of studies on the distribution of these elements in the Southern Ocean, and even less studies examining the chemical speciation of these elements. Recent studies have also indicated that sub-optimal Zn concentrations may greatly influence Si and N uptake rates by phytoplankton while the Co containing vitamin B12 may be present in the Southern Ocean at potentially limiting concentrations for some diatom species however for both elements direct evidence is still missing. Thus presently we urgently require a comprehensive study encompassing the chemical speciation and distribution of the already identified key bio-elements (Co, Ni, Cd and Zn) over a range of different Fe and macronutrient conditions. Overall such a study will not only improve our understanding of trace metal biogeochemical cycling in the Southern Ocean but also greatly increase our understanding as a whole of nutrient biogeochemistry in this key climatic region. As part of the GEOTRACES contribution to ANT-XXIV/3 the lfM-GEOMAR Aqueous Trace Oxidant and Metal Speciation Laboratory (ATOMSLab) has 3 main research areas funded by the DFG: 1. Does Fe control the biogeochemical cycling, speciation and distribution of Cd, Zn, Ni and Co in the Southern Ocean? 2. Development of a budgetary scheme for Cd, Zn, Ni and Co in the Southern Ocean, including both concentrations of various inorganic and organic pools, size ranges and the fluxes between them. 3. What controls trace metal solubility (Fe, Al and Ti) in the ocean? The overall aim of this work is to combine the results of the objectives listed above into a comprehensive model of the key processes affecting the biogeochemistry of the Cd, Zn, Co, Ni and Ti in the Southern Ocean. 3.2.1 Cadmium, cobalt, nickel and zinc speciation in the Southern Ocean Oliver Baars and Peter Croot IfM-GEOMAR Objectives Our main objective during ANT-XXIV/3 was to examine the speciation and biogeochemistry of other bio-relevant elements (Cd, Co, Ni and Zn) in the iron limited Southern Ocean. While Fe is the primary control for phytoplankton productivity in this region, the elements we are investigating have also been identified as being important for structuring the phytoplankton community and the macronutrient drawdown during bloom situations. The interplay between the Fe biogeochemical cycle and the physical oceanography of the region with the elements we are studying is important for understanding their global cycling. By comparison of the chemistries and distributions of Cd, Zn, Co and Ni this IPY GEOTRACES study is aiming to improve our knowledge of the processes effecting trace metal distributions in the ocean with emphasis on the iron limited Southern Ocean. Introduction Zn Biogeochemistry - zinc is an element that is required for many enzymatic processes and from a marine prospective chief amongst these are its role in carbonic anhydrase (Lane and Morel, 2000b) and in zinc finger proteins for DNA transcription (Armbrust et al., 2004). Vertical profiles of Zn show a strong nutrient like profile (Bruland et al., 1979; Nolting and De Baar, 1994), with strong similarity to silicate. In surface waters Zn is present as weak organic complexes (Bruland, 1989; Ellwood, 2004; Ellwood and van den Berg, 2000) that lower the free zinc concentrations to sub pM levels which based on laboratory studies could be potentially limiting for phytoplankton (Brand et al., 1983; Buitenhuis et al., 2003; Shaked et al., 2006; Sunda and Huntsman, 1992; Sunda and Huntsman, 1995; Sunda and Huntsman, 2005). However deckboard incubation experiments in HNLC regions (Coale, 1991; Coale et al., 2003; Crawford et al., 2003) have yet to clearly show any strong effect on productivity but have shown differences in N and Si assimilation rates (Franck et al., 2003). There have been a few published studies on Zn distributions in the Southern Ocean; Ross Sea (Fitzwater et al., 2000), Drakes Passage and Gerlache Strait (Martin et al., 1990) and in the Weddell Sea (Nolting and De Baar, 1994; Westerlund and Ohman, 1991). There have been no studies of Zn speciation reported yet from Southern Ocean waters. Cd Biogeochemistry - It is yet to be demonstrated that cadmium is an essential element for phytoplankton growth and normally it is toxic at levels just above ambient seawater (Brand et al., 1986). However recently it has been shown that there is a cadmium containing isoform, found in some marine diatoms, of the usual zinc containing enzyme carbonic anhydrase (Lane and Morel, 2000a; Lane et al., 2005). This apparent biological utilization of Cd (Lee and Morel, 1995; Lee et al., 1995; Price and Morel, 1990) may explain why this element has a strong nutrient like profile in seawater with strongest similarity to phosphate. The Cd-phosphate relationship in the global ocean has been studied extensively particularly with regard to the Southern Ocean (Frew and Hunter, 1992; Löscher et al., 1998; Nolting and De Baar, 1994). The true nature of the relationship between Cd and phosphate in the Southern Ocean is an important area of study as Cd:Ca ratios in forams are commonly used as a paleotracer for P043 (Boyle, 1988; Boyle et al., 1995). Iron and Zn bioavailabilty along with CO2 concentrations may influence the Cd:P ratio in phytoplankton (Cullen et al., 2003; Cullen et al., 1999; Cullen and Sherrell, 2005). During the Southern Ocean iron enrichment experiments SOIREE (Frew et al., 2001) and EIFeX (Croot in prep) there was a considerable conversion of dissolved Cd into particulate forms with an apparently high Cd:P ratio, while Zn remained mostly in the dissolved phase. This phenomena is currently difficult to explain though it may be due to differences in the bioavailabilty of Cd compared to Zn, due to weak Cd organic complexation (Bruland, 1992; Ellwood, 2004). There have been no published studies to data of Cd speciation in the main Southern Ocean water masses, with studies limited to the coastal Ross Sea (Biesuz et al., 2006; Capodaglio et al., 1991; Capodaglio et al., 2002) and the subantarctic waters close to New Zealand (Ellwood, 2004). None of the studies published so far have included the important effects of Fe limitation on the Cd speciation. Co Biogeochemistry - Cobalt is present in seawater at low pM concentrations (Jickells and Burton, 1988) and shows depletion in surface waters with typically a maximum in intermediate waters. Recent work has shown that Co can replace Zn in carbonic anhydrase (Lane and Morel, 2000b; Price and Morel, 1990; Yee and Morel, 1996) and that this Co-Zn inter-replacement may determine the dominance of either diatoms or coccolithophorids (Sunda and Huntsman, 1995), though other studies have shown that not all phytoplankton can utilise Co instead of Zn (Timmermans et al., 2001). Co is also the central metal atom in several key vitamins such as Bi 2, but not all phytoplankton apparently require B12 (Swift, 1981). In surface seawater Co(l1) is believed to be strongly organically complexed (Ellwood and Berg, 2001; Ellwood et al., 2005; Saito and Moffett, 2001; Zhang et al., 1990) though a recent study suggested that some of this apparently complexed Co(II) may be inert Co(III) (van Leeuwen et al., 2005) based on the expected dissociation kinetics for Co(II) complexes. Only one speciation study has been carried out in the vicinity of the Antarctic Polar Front (APF) on samples obtained during the Polarstern cruise ANT-XVI/3 (Ellwood et al., 2005). In this study Co speciation was found to be dominated by inorganic complexes north of the APF, while to the south organic complexation was more important, giving rise to a large gradient in the free Co concentration in the southern surface waters. How this change in Co bioavailabilty may affect phytoplankton productivity or community structure was not immediately clear though the authors noted that south of the APF the system was dominated by diatoms who may have a lower Co requirement than other phytoplankton species. There are few measurements of Co from the Southern Ocean: low levels for Co (2040 pM) in the Drake Passage (Martin et al., 1990) with similarly low levels (20-40 pM) in the adjacent Weddell Sea (Westerlund and Öhman, 1991) and in the Ross Sea (Fitzwater et al., 2000) though a more recent study found elevated levels close to the Antarctic Peninsula and Deception Island in the Weddell Sea (Sanudo-Wilhelmy et al., 2002). Ni Biogeochemistry - nickel is a required element for the enzyme urease, which phytoplankton use to break down urea into ammonia. Laboratory studies have shown that Ni deficiency can affect N uptake in the form of urea (Price and Morel, 1991). Ni also has a nutrient like vertical distribution in the ocean and studies (Donat and Bruland, 1988; Donat et al., 1994; van den Berg and Nimmo, 1987) have indicated it to be weakly organically complexed with up to 20 % in some unreactive form (Wen et al., 2006). The kinetics of Ni(II) water loss are slow (Hudson and Morel, 1993; Morel et al., 1991) and so equilibrium with organic complexes can take many hours to come to completion, much longer than the duration of many of the published experiments leaving the possibility that the "unreactive" Ni is only very slowly exchangeable but not necessarily inert. There are no published reports on Ni speciation from the Southern Ocean and only a handful of studies on its distribution; high levels for Ni (4-8 nM) in the Ross Sea (Fitzwater et al., 2000) with similar levels in the Weddell Sea (Nolting and De Baar, 1994; Westerlund and Öhman, 1991). Work at sea Water Sampling In the present work we obtained vertical profiles for these elements along the transects in the different regions of the Southern Ocean surveyed during ANT-XXIV/3 as part of the IPY GEOTRACES ZERO and DRAKE research programme (Fig. 3.15). Depth resolved sampling was performed using water collected the NIOZ ultraclean (Al cast) winch. Trace metal sampling for zinc and cadmium speciation Samples for zinc (Bruland, 1989) and cadmium (Bruland, 1992) speciation were measured at sea in the lfM-GEOMAR Class 100 Clean room container using anodic stripping voltammetry (ASV) with a mercury film electrode plated on a rotating disk electrode (MFE-RDE). Pseudo polarograms were also made from selected stations to examine the Zn and Cd speciation further. Trace metal sampling for total zinc, cadmium, nickel and cobalt Samples were collected for total dissolved concentration and acidified on board for later analysis in Kiel using standard methods for trace metals. Speciation sampling for nickel and cobalt Samples were collected for dissolved speciation analysis of Ni and Co for later in Kiel. Samples were immediately frozen and will be thawed only immediately prior to analysis. Laboratory work will focus on kinetic aspects of the speciation of these elements at the ambient temperatures found in Southern Ocean waters. These measurements were not made at sea due to the slow kinetics of these two metals which then requires several days of experimental time to make the required measurements. Preliminary results During ANT-XXIV/3 we sampled 15 stations at sea for Cd and Zn speciation and an equal number for total dissolved metal concentrations (Cd, Co, Cu, Fe, Ni, Zn) which will be analysed later in the laboratory in Kiel. Samples from 6 stations were also frozen for later analysis for Ni and Co speciation. At all stations we observed strong gradients in electroactive (labile) Zn and Cd, by which the labile metal concentration increased with depth (Fig. 3.16). It also appeared that Cd and Zn ligands were present mostly in the surface waters and were not so abundant at depth with Cd ligands more important in controlling the speciation. Pseudopolarography also confirmed this interpretation as for zinc only a single inorganic wave was observed while for Cd two distinct waves could be seen suggesting the presence of a reducible organic species in the seawater. Further laboratory work should help to confirm these original findings. Later work will also involve examining the metal :nutrient ratios found in the different water masses during ANT-XXIV/3. Acknowledgments The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Thanks to the winch operating and tapping crew of the Ultraclean Al cast who provided all the samples for this study - in particular Michael Stimac for taking on a second job at short notice. Thanks also to the Chief Scientist, Dr Eberhard Fahrbach and to the AWI Logisitics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG (CR145/10) and lfM-GEOMAR. Fig. 3.15: Location of the stations during ANT-XXIV/3 where measurements were made for Cd and Zn speciation. (left) Greenwich meridian, (centre) Weddell Sea and (right) in Drake Passages. Fig. 3.16: Cd and Zn vertical profiles from the Drake Passage (Station 230) References Armbrust, E.V. et al., 2004. The Genome of the Diatom Thalassiosira Pseudonana: Ecology, Evolution, and Metabolism. Science, 306(5693): 79- 86. Biesuz, R., Alberti, G., D'Agostino, G., Magi, E. and Pesavento, M., 2006. 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Marine Chemistry, 28: 285-300. 3.2.2 Copper speciation in the Southern Ocean: Implications for reactions with superoxide Maija Heller and Peter Croot IfM-GEOMAR Objectives Our primary objective during ANT-XXIV/3 was to examine the chemical speciation of copper in the water column of the Southern Ocean and to determine whether Cu speciation played a significant role in superoxide reactivity. Superoxide is difficult to measure in the ocean because it is extremely reactive, particularly with trace metals, and has a short half-life. It is however important in metal cycling as it can shuffle metals between different redox states with differing biogeochemical properties. This is most evident in the case of Cu and Fe where the oxidized forms are thermodynamically favored in seawater but are less soluble and less reactive than the reduced forms - thus Fe(II) is more bioavailable and soluble than Fe(lII). Amongst the biogeochemically important trace metals Cu has the fastest kinetic reactivity and is thus the main candidate for controlling superoxide reactivity in seawater. Introduction Importance of copper to oceanic productivity Copper is an important component of respiratory proteins and oxidases (Baron et al., 1995) and as such is a required element for phytoplankton. However even at the low level of free copper (Cu2 ) concentrations found in the environment (pM to nM), cell division rates of phytoplankton in culture have been shown to be dramatically reduced, particularly for cyanobacteria (Brand et al., 1986). Elevated free Cu2 in phytoplankton cells can decrease photosynthetic rates (Baron et al., 1995), competitively inhibit the uptake of other essential metals such as Mn (Sunda et al., 1981; Sunda and Huntsman, 1983; Sunda and Huntsman, 1998) and disrupt enzyme function through binding to thiol groups(-SH) or from reactions with oxygen species to from the damaging hydroxyl radical (Stauber and Florence, 1987). Copper speciation in seawater Dissolved copper in seawater has been found to be efficiently complexed by strong organic ligands, of unknown functionality, but believed to be biologically produced (Coale and Bruland, 1988; Moffett et al., 1990; van den Berg, 1984). This organic complexation of Cu greatly reduces the free copper concentration to below 1 pM in most open ocean waters and unpolluted coastal waters (Moffett, 1995; Moffett et al., 1997), a level at which most phytoplankton are not Cu stressed (Brand et al., 1986). Copper redox speciation In oxygenated seawater the thermodynamically favoured redox state of Cu is Cu(ll), however there are several important redox reactions involving Cu(II) that could see cycling between Cu(l) and Cu(II) with significant concentrations of Cu(l) present in surface waters (Moffett and Zika, 1988). Most notably Cu(l) could be produced by processes including: (i) Photochemical reduction of Cu organic complexes (Ferraudi and Muralidharan, 1981; Wu et al., 2000). (ii) Reduction of Cu (11) by H202 (Moffett and Zika, 1987; Moffett and Zika, 1988). (iii) Biologically mediated reduction of Cu(II) to Cu(l) (Hassett and Kosman, 1995; Jones et al., 1987; Jones et al., 1985). There have been several studies into the oxidation of Cu(l) in seawater (Moffett and Zika, 1987; Sharma and Millero, 1988a; Sharma and Millero, 1988b; Sharma and Millero, 1989) and in general Cu(l) oxidation in the open ocean is controlled through oxidation by 02 as the reaction with H202 is significantly slower under typical open ocean conditions. A generalised mechanism for the oxidation of Cu(I) has been proposed: Cu(^+) + O(2) → Cu(^2+) + O(2)(^-) slow Cu(^+) + O(2)(^-) → Cu(^2+) + H(2)O(2) fast Cu(^+) + H(2)O(2) → Cu(^2+) + OH˙ + OH(^-) slow Cu(^+) + OH˙ → Cu(^2+) + OH(^-) fast For the reduction of Cu(II) by H(2)O(2) the following mechanism has also been proposed: H(2)O(2) ↔ H(^+) + HO(2)(^-) fast Cu(^2+) + HO(2)(^-) → Cu(^+) + HO(2) slow HO(2) → H(^+) + O(2)(^-) fast Cu(^2+) + O(2)(^-) → Cu(^+) + O(2) fast The Cu(II) reduction rate increases in the presence of strong Cu(I) binding ligands. At low concentrations of Cu, the 02 formed may react via different pathways, notably that of reactions with Fe(II/III) and CDOM (Goldstone and Voelker, 2000; Voelker et al., 2000). Superoxide Superoxide is produced in seawater by predominantly photochemical pathways, though biological production may also be important. Model studies suggest that superoxide would be found in seawater at sub nM levels due to its rapid reactions with metals (Cu, Fe) and organic matter. However at present there are no direct measurements of superoxide in seawater published to confirm this and initial reports suggest steady state superoxide levels may be in the tens of nMs in sunlit open ocean seawater. The half-life of superoxide is relatively short (Millero, 1987) due to a combination of the dismutation reaction to form peroxide and reactions with metals such as Cu and Fe. In the present work we examined the influence of Cu speciation on superoxide half-lifes in seawater as a tool to probe metal redox reactivity in seawater. Water sampling In the present work we obtained vertical profiles for total Cu along the transects in the different regions of the Southern Ocean surveyed during ANT-XXIVI3 as part of the IPY GEOTRACES ZERO and DRAKE research programme. Depth resolved sampling was performed using water collected the NIOZ Ultraclean (Al cast) winch. Speciation measurements were only performed in the Weddell Sea and in the Drake Passage (Fig. 3.17). Copper speciation determination Copper speciation measurements were made using the ligand Salicylaldoxime (SA) with the voltametric method of Cam pos and van den Berg (1994). For each station 6 samples from throughout the water column were analysed using two detection windows (1 µM and 2 µM SA). The data was analysed using a non-linear optimization of a Langmuir isotherm (Gerringa et al., 1995). Superoxide determination using MCLA In order to determine superoxide at nM concentrations in seawater we employed the reagent MCLA ([2-methyl-6-(4-methoxyphenyl)-3,7- dihydroimidazo[1, 2-a]pyrazin-3-one, HCl]) which is a commonly used chemiluminescent technique for the determination of superoxide in aqueous solutions. A FIA (Waterville Analytical Maine, USA) system was used to follow the reaction of the MCLA with an addition of an aliquot of superoxide to seawater samples from different depths, which had been amended with either DTPA (to observe only the superoxide dismutation reaction), Fe or Cu (both added at nM levels). Preliminary results Speciation measurements for Cu were made at 8 stations during ANT- XXIV/3. In general we found stronger complexation in surface waters than in deeper waters. This relationship was also reflected in the superoxide reactivity experiments where deep samples had reduced superoxide lifetimes and this was further reduced upon addition of Cu (Fig. 3.18) and to a lesser extent Fe. Surface water samples had an excess of metal complexing ligands and no change in superoxide reactivity was seen for the metal additions. The complete data set will be analysed once the samples for Total Cu are analysed in the laboratory in Kiel. Acknowledgements The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Thanks also to the Chief Scientist, Dr Eberhard Fahrbach and to the AWI Logistics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG (CR145/15) and lfM-GEOMAR. Fig. 3.17: Map of the station locations at which samples were analysed for Cu speciation and reactivity with superoxide Fig. 3.18: Depth profiles of superoxide kinetics in seawater. (left) 1st order rate constants for the destruction of superoxide in seawater amended with Cu. (right) 1st order rate constants for the destruction of superoxide in seawater amended with Fe. References Baron, M., Arellano, J.B. and Gorge, J.L., 1995. Copper and photosystem II: A controversial relationship. Physiologia Plantarum, 94: 174-180. Brand, L.E., Sunda, W.G. and Guillard, R.R.L., 1986. Reduction of Marine Phytoplankton Reproduction Rates by Copper and Cadmium. Journal of Experimental Marine Biology and Ecology, 96: 225-250. Campos, M.L.A.M. and van den Berg, C.M.G., 1994. Determination of copper complexation in sea water by cathodic stripping voltammetry and ligand competition with salicylaldoxime. Analytica Chimica Acta, 284: 481-496. Coale, K.H. and Bruland, K.W., 1988. Copper complexation in the northeast Pacific. Limnology and Oceanography, 33: 1084-1101. Ferraudi, G. and Muralidharan, 5., 1981. Photochemical properties of copper complexes. Coordination Chemistry Reviews, 36: 45-88. Gerringa, L.J.A., Herman, P.M.J. and Poortvliet, T.C.W., 1995. Comparison of the linear van den Berg/Ruzic transformation and a non- linear fit of the Langmuir isotherm applied to Cu speciation data in the estuarine environment. Marine Chemistry, 48: 131-142. Goldstone, J.V. and Voelker, B.M., 2000. Chemistry of Superoxide Radical in Seawater: CDOM Associated Sink of Superoxide in Coastal Waters. Environmental Science and Technology, 34:1043-1048. Hassett, R. and Kosman, D.J., 1995. Evidence for Cu(II) Reduction as a Component of Copper Uptake by Saccharomyces cerevisiae. The Journal of Biological Chemistry, 270: 128-134. Jones, G.J., Palenik, B.P. and Morel, F.M.M., 1987. Trace Metal Reduction by Phytoplankton: the role plasmalemma redox enzymes. Journal of Phycology, 23: 237-244. Jones, G.J., Waite, T.D. and Smith, J.D., 1985. Light-Dependent Reduction of Copper(II) and its effect on Cell-Mediated, Thiol- Dependent Superoxide Production. Biochemical and Biophysical Research Communications, 128:1031-1036. Millero, F.J., 1987. Estimate of the life time of superoxide in seawater. Geochimica et Cosmochimica Acta, 51: 351-353. Moffett, J.W., 1995. Temporal and Spatial Variability of Copper Complexation by Strong Chelators in the Sargasso Sea. Deep Sea Research, 42: 1273-1295. Moffett, J.W., Brand, L.E., Croot, P.L. and Barbeau, K.A., 1997. Cu speciation and cyanobacterial distribution in harbors subject to anthroprogenic Cu inputs. Limnology and Oceanography, 42: 789-799. Moffett, J.W. and Zika, R.G., 1987. Reaction Kinetics of Hydrogen Peroxide with Copper and Iron in Seawater. Environmental Science and Technology, 21: 804-810. Moffett, J.W. and Zika, R.G., 1988. Measurement of copper(I) in surface waters of the subtropical Atlantic and Gulf of Mexico. Geochimica et Cosmochimcia Acta, 52: 18491857. Moffett, J.W., Zika, R.G. and Brand, L.E., 1990. Distribution and potential sources and sinks of copper chelators in the Sargasso Sea. Deep-Sea Research, 37: 27-36. Sharma, V.K. and Millero, F.J., 1988a. Effect of Ionic Interactions on the rates of Oxidation of Copper(l) with 02 in Natural waters. Marine Chemistry, 25: 141-161. Sharma, V.K. and Millero, F.J., 1988b. Oxidation of Copper(l) in Seawater. Environmental Science & Technology, 22: 768-771. Sharma, V.K. and Millero, F.J., 1989. The oxidation of Cu(l) with H202 in natural waters. Geochimica et Cosmochimica Acta, 53: 2269-2276. Stauber, J.L. and Florence, TM., 1987. Mechanism of toxicity of ionic copper and copper complexes to algae. Marine Biology, 94: 511-519. Sunda, W.G., Barber, R.T. and Huntsman, S.A., 1981. Phytoplankton growth in nutrient rich seawater: importance of copper-manganese cellular interactions. Journal of Marine Research, 39: 567-586. Sunda, W.G. and Huntsman, S.A., 1983. Effect of competitive interactions between manganese and copper on cellular manganese and growth in estuarine and oceanic species of the diatom Thalassiosira. Limnology and Oceanography, 28: 924-934. Sunda, W.G. and Huntsman, S.A., 1998. Interactive effects of external manganese, the toxic metals copper and zinc, and light in controlling cellular manganese and growth in a coastal diatom. Limnology and Oceanography, 43:1467-1475. van den Berg, C.M.G., 1984. Determination of the complexing capacity and conditional stability constants of complexes of Cu(II) with natural organic ligands in seawater by cathodic stripping voltammetry of copper-catechol complex ions. Marine Chemistry, 15: 118. Voelker, B.M., Sedlak, D.L. and Zafiriou, O.C., 2000. Chemistry of Superoxide Radical in Seawater: Reactions with Organic Cu Complexes. Environmental Science and Technology, 34: 1036-1042. Wu, C.-H., Sun, L. and Faust, B.C., 2000. Photochemical Formation of Copper(I) from Copper(I 1)-Dicarboxylate Complexes: Effects of Outer- Sphere versus Inner -Sphere Coordination and of Quenching by Malonate. Journal of Physical Chemistry A, 104: 49894996. 3.2.3 Iron solubility in the Southern Ocean Maija Heller and Peter Croot IfM-GEOMAR Objectives In collaboration with the group of Hein de Baar from NIOZ we examined the solubility of iron in water samples from the Southern Ocean. This study seeks to determine the processes (complexation, scavenging, redox state) that contribute to the distribution of iron in deep waters and in the long term transport of iron through the deep ocean. The main goal of this work is to determine what controls the solubility of dissolved iron in deep waters. Introduction Iron is poorly soluble in seawater and careful laboratory measurements of inorganic iron solubility (cFes) by Byrne et al. (2005), Kuma et al. (1996) and a Fe solubility model of Liu and Millero (1999; 2002) suggest that cFes depends on salinity, temperature, pH, with higher concentrations of soluble Fe possible at lower temperatures, lower pHs, and higher salinities. Fe solubility in both UV irradiated and artificial seawater (i.e. seawater containing no dissolved organic matter (DOM)), at 0.01 nM between pH 7.5 and 9, has been shown to be lower than in untreated seawater (cFes = 0.5 nM) (Liu and Millero, 2002). This difference can be explained by the existence of natural organic ligands (Kuma et al., 1996; Liu and Millero, 2002) which enhance the Fe solubility in seawater by organic complexation of the trace metal. More recently iron solubility in deep waters has been found to be linearly correlated to the concentrations of macronutrients (e.g., NOR) (Kuma, 2002; Tani et al., 2003) possibly due to the release of organic ligands during the microbial decomposition of sinking particulate organic matter (POM). The regeneration of fluorescent humic substances has been observed during organic matter decomposition (and consistent with the correlation of nutrients and apparent oxygen utilization (AOU)) in the water column (Hayase and Shinozuka, 1995; Hayase et al., 1988). Some humic substances, such as humic acid, can function as Fe binding ligands, increasing Fe solubility at pH 8 by organic complexation. Alternatively, Fe binding ligands are released by bacteria (Haygood et al., 1993; Martinez et al., 2000; McCormack et al., 2003), and could be associated with the growth of the population of heterotrophic bacteria decomposing the organic matter. In the present work we undertook to examine Fe solubility in deep waters from the Southern Ocean for the first time to see if the same apparent processes were occurring there as in the North Pacific (Studies of Kuma et al., 2002). This work also follows up previous work conducted during ANT-XXIII/9 which focused solely on surface waters. Work at sea Sampling of subsurface seawater Seawater samples were obtained throughout the water column using the NIOZ ultraclean rosette during ANT-XXIV/3 (Fig. 3.19). The seawater was filtered through 0.2 pm membrane filters (Sartorius) under nitrogen overpressure (0.2 - 0.3 bar) into 125 mL acid cleaned LDPE bottles (Kartell). All sample handling was performed under Class 100 Clean room conditions. The samples were frozen at -20°C and transported back with Polarstern to Germany for later analysis in the laboratory in Kiel. Sample treatment Fe solubility measurements will be performed on thawed aliquots of the previously frozen samples using the radioisotope 55 Fe (Hartmann Analytics, Braunschweig, Germany). The experimental setup (described below) is adapted from Kuma et al. (2002) and is briefly described: An addition of 20 nM 55 Fe (to = Oh; pH 7.9) is made to each sample, and a small subsample (roughly 9 mL) is filtered through a 0.02 pm Anotop syringe filter (Whatman) previously flushed and rinsed with MO water. The first 6 - 7 mL of the filtrate is discarded in order to avoid dead volume artifacts. The next 1 - 2 mL of filtrate is placed in a 60 mL acid cleaned Teflon bottle and acidified with OD-HCI, to keep the Fe from adsorbing to the bottle walls (Fischer et al., 2007). Duplicates of unfiltered and 002 pm filtered samples (400 pL) are transferred into 6 mL counting vials to which 4.5 mL of scintillation fluid (Lumagel Plus(r)) are then added. The same procedure is repeated for subsamples taken after 3, 6, 24, 48 and 72h. After filtration and cocktail addition, vials are capped and placed in a liquid scintillation counter (Packard, Tri-Carb 2900TR) where each sample is counted for 30 minutes. Counts per minute are then converted to soluble Fe concentrations, taking into account the activity of the added isotope solution and the dissolved Fe concentration of each sample. Preliminary results There are no results at present as the samples still need to be analysed in the laboratory in Kiel. We anticipate however that the results will be complementary to data recently obtained during ANT- XXIIII9 in the Weddell Sea and Kerguelen Plateau. Using this approach we will obtain information about iron solubility in this region and data on the kinetics of Fe exchange between soluble and particulate forms. This study is a comparison study with work performed within the BMBF project SOPRAN (D-SOLAS) which examines iron cycling in the surface ocean under the Saharan dust plume. Acknowledgements The authors would like to show their deep thanks and appreciation to the officers and crew of Polarstern, for all their efforts in helping us throughout the duration of ANTXXIV/3. Thanks also to the Chief Scientist, Dr Eberhard Fahrbach and to the AWI for making this cruise possible. Special thanks to our GEOTRACES colleagues from the Netherlands who operated and performed the sampling programme with the Ultraclean winch during this cruise. This work was made possibly specifically through funding from the DFG (CR145/lU and CR145/iS) and lfM-GEOMAR. Fig. 3.19: Locations during ANT-XXIV/3 where vertical profiles were taken for iron solubility measurements (left) Greenwich meridian and (right) Drake Passage. One further station was sampled in the centre of the Weddell Sea. References Byrne, RH., Yao, W., Luo, Y. and Wang, B., 2005. The dependence of Fe(III) hydrolysis on ionic strength in NaCI solutions. marchem, 97: 34- 48. Fischer, AC., Kroon, J.J., Verburg, T.G., Teunissen, 1. and Wolterbeek, HI., 2007. On the relevance of iron adsorption to container materials in small-volume experiments on iron marine chemistry: 55Fe-aided assessment of capacity, affinity and kinetics. Marine Chemistry, 107(4): 533-546. Hayase, K. and Shinozuka, N., 1995. Vertical distribution of fluorescent organic matter along with AOU and nutrients in the equatorial Central Pacific. Marine Chemistry, 48(3-4): 283290. Hayase, K., Tsubota, H., Sunada, I., Goda, S. and Yamazaki, H., 1988. Vertical distribution of fluorescent organic matter in the North Pacific. Marine Chemistry, 25(4): 373. Haygood, MG., Holt, P.D. and Butler, A., 1993. Aerobactin production by a planktonic marine Vibrio sp. Limnol. Oceanogr., 38(5): 1091-1097. Kuma, K., 2002. Variation in iron(III) solubility and iron concentration in the northwestern North Pacific Ocean. Limnol. Oceanogr., 47(3): 885-892. Kuma, K., Nishioka, J. and Matsunaga, K., 1996. Controls on iron(III) hydroxide solubility in seawater: The influence of pH and natural organic chelators. Limnol. Oceanogr., 41(3): 396-407. Liu, H. and Millero, F.J., 1999. The solubility of iron hydroxide in sodium chloride solutions. Geochim. Cosmochim. Act., 63(19/20): 3487- 3497. Liu, X. and Millero, F.J., 2002. The solubility of iron in seawater. Mar. Chem., 77: 43-54. Martinez, J.S. et al., 2000. Self-Assembling Amphiphilic Siderophores from Marine Bacteria. Science, 287:1245-1247. McCormack, P., Worsfold, P.J. and Gledhill, M., 2003. Separation and Detection of Siderophores Produced by Marine Bacterioplankton Using High-Performance Liquid Chromatography with Electrospray Ionization Mass Spectrometry. Anal. Chem., 75: 26472652. Tani, H. et al., 2003. Iron(III) hydroxide solubility and humic-type fluorescent organic matter in the deep water column of the Okhotsk Sea and the northwestern North Pacific Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 50: 1063-1078. 3.2.4 Titanium in the Southern Ocean Peter Croot and Maija Heller IfM-GEOMAR Objectives As part of the IPY GEOTRACES ZERO and DRAKE programme we planned to take the first deep water measurements of titanium from the Southern Ocean. This information should allow us to better constrain the residence time of Ti in the ocean and to examine the fluxes and important processes occurring between the different oceanic basins. Introduction While it is established now that Fe can be a (co)limiting nutrient for phytoplankton in High Nutrient Low Chlorophyll (HNLC) regions of the world we still know little about the processes by which Fe is supplied to the ocean and how processes in the ocean scavenge/uptake or remineralize dissolved Fe. In many cases examination of other elements similar in chemistry to iron reveals more information on the key processes involved - such elements include Ti(IV), AI(III) and Mn(ll). By comparison of the concentrations of these strongly hydrolysed elements in the soluble, dissolved and particulate phases we hope to be able to better understand the processes affecting dust dissolution and particle scavenging in the surface ocean. Titanium biogeochemistry in seawater has been studied very little in the open ocean, with only a single deep-water profile from the Pacific (Orians and Boyle, 1993; Orians et al., 1990) which showed picomolar concentrations in surface waters and increasing to -300 pM in deep waters. There have been a few more studies in enclosed seas (van den Berg et al., 1994) and estuaries (Skrabal, 1995; Skrabal and Terry, 2002; Skrabal et al., 1992) but overall there is little information on the global Ti distribution in the ocean. Based on the work of Orians et al. (1990) Ti has a short residence time in the ocean and is enriched with depth due to remineralisation processes, there are presently no measurements from the Southern Ocean. For the Southern Ocean, the small data set from other regions hints that there may be significant differences in Ti concentrations between the different water masses present. In the present study, through the use of a new voltametric technique, developed at lfM-GEOMAR, that allows shipboard determination of pM levels of Ti, we were set to test this hypothesis. By comparison of the chemistries and distributions of Ti, Al, Mn and Fe this GEOTRACES study in cooperation with NIOZ colleagues is aiming to improve our knowledge of the processes effecting trace metal distributions in the ocean with emphasis on dust deposition. The work performed during ANT-XXIV/3 was part of the German contribution for GEOTRACES and is also a continuation of similar earlier work performed on the Polarstern (ANT-XVIII/1 and ANT-XXIII/1) (Bowie et al., 2003; Sarthou et al., 2003) and the Meteor (M55) (Croot et al., 2004). Work at sea Water sampling In the present work we obtained vertical profiles for Ti along the transects in the different regions of the Southern Ocean surveyed during ANT-XXIV/3 as part of the IPY GEOTRACES ZERO and DRAKE research programme. Depth resolved sampling was performed using water collected with both the regular CTD (Bl cast) and the NIOZ Ultraclean (Al cast) winch. Trace metal sampling - analysis and examination of storage protocols Samples were analysed for Ti(IV) using a new voltametric method developed at lfMGEOMAR (Croot, in preparation). All samples were analyzed unfiltered and within 24 hours of collection. Archive samples were also taken for later analysis in the laboratory in Kiel to examine possible storage artefacts as Ti is a ubiquitous component of the conventional trace metal sampling bottles as it is used a whitening agent (Ti02) or as a catalyst in the preparation of plastics (similar problems exist for Al). Preliminary results During ANT-XXIV/3 we made on board analysis of 15 stations for Titanium (Fig. 3.20) with 3 in the Drake Passage and 12 along the Greenwich meridian. Problems were encountered with the 3 stations taken from the ultraclean rosette, presumably due to its titanium construction but this may also have been due to sampling artefacts. The normal CTD (Bi cast) seemed to be fine for Ti sampling as was found in past cruises on the Polarstern. In general Ti increased with depth at all stations (Fig. 3.21) and further work will examine if there are discernable differences in the Ti content between the different deep water masses present along the transects. Acknowledgements The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Thanks also to the Chief Scientist, Dr. Eberhard Fahrbach and to the AWI Logistics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG (CR145/15) and lfM-GEOMAR. Fig. 3.20: Bathymetrical map of the Atlantic sector of the Southern Ocean showing the location of stations sampled (blue triangles) during ANT-XXIV/3, the cruise track is also shown as a thin blue line. Fig. 3.21: Profile of labile Ti in the water column near the shelf edge close to Neumayer Station References Bowle, A.R. et al., 2003. Shipboard intercomparison of dissolved iron in surface waters along a north-south transect of the tropical Atlantic Ocean. Marine Chemistry, 84:19-34. Croot, P.L., Streu, P. and Baker, AR., 2004. Short residence time for iron in surface seawater impacted by atmospheric dry deposition from Saharan dust events. Geophysical Research Letters, 31: L23S08, doi.1029/2004GL020153. Orians, K.J. and Boyle, E.A., 1993. Determination of Picomolar Concentrations of Titanium, Gallium and Indium in Sea-Water by Inductively-Coupled Plasma-Mass Spectrometry Following an 8- Hydroxyquinoline Chelating Resin Preconcentration. Analytica Chimica Acta, 282(1): 63-74. Orians, K.J., Boyle, E.A. and Bruland, K.W., 1990. Dissolved titanium in the open ocean. Nature, 348: 322-325. Sarthou, G. et al., 2003. Atmospheric iron deposition and sea-surface dissolved iron concentrations in the East Atlantic. Deep-Sea Research, 50: 1339-1352. Skrabal, S.A., 1995. Distributions of Dissolved Titanium in Chesapeake Bay and the Amazon River Estuary. Geochimica Et Cosmochimica Acta, 59(12): 2449-2458. Skrabal, S.A. and Terry, CM., 2002. Distributions of dissolved titanium in porewaters of estuarine and coastal sediments. Marine Chemistry, 77: 109-122. Skrabal, S.A., UlIman, W.J. and Luther, G.W., 1992. Estuarine distributions of dissolved titanium. Marine Chemistry, 37: 83-103. van den Berg, C.M.G., Boussemart, M., Yokoi, K., Prartono, 1. and Campos, M.L.A.M., 1994. Speciation of aluminium, chromium and titanium in the NW Mediterranean. Marine Chemistry, 45: 267-282. 3.2.5 Elemental ratios in particulate samples from the Atlantic sector of the Southern Ocean Peter Croot(1), Oliver Baars(1) and (1)IfM-GEOMAR Rob Sherrell(2), not on board (2)Rutgers University Objectives Our goal during ANT-XXIV/3 was to obtain samples for particulate metals from along the surveyed transects in order to have material from a variety of different oceanic environments in the Southern Ocean. Particulate samples were taken simultaneously, and in cooperation with the Dutch and German teams on board sampling in the dissolved phase in order to facilitate interpretation of the collected samples. Introduction Trace element ratios in particulate matter from surface waters reflect the nature of the particles themselves and can provide information on the processes that formed them. In particular in regions of high productivity the content of the mostly organic particles reflect the concentrations of the bioavailable fraction of the metals in seawater; this may include changes in the Cd:P or Zn:P ratio or in the Fe:P ratio. In contrast in shallow coastal regions, the particles may reflect more the inorganic/crustal signature of the nearby land or underlying sediments. The Rutgers group of Prof. Rob Sherrell have a strong history of developing and applying ICPMS techniques to the problem of element ratios in particulate matter (Berman-Frank et al., 2001; Cullen and Sherrell, 1999; Cullen et al., 1999; Cullen et al., 2003; Field et al., 1999; Sterner et al., 2004). By measuring elemental ratios in particles collected during ANT-XXIV/3 we hope to gather further information on the way in which particle supply and production, scavenging and dissolution controls dissolved metal concentrations in the open ocean and in turn how this may affect primary productivity. Work at sea Sampling Methodology In the present work we obtained surface and near surface samples along the transects in the different regions of the Southern Ocean surveyed during ANT-XXIV/3 as part of the IPY GEOTRACES ZERO and DRAKE research programme. Sampling was conducted in two modes: (i) Occasional surface sampling from the Iron-FISH. This involved collecting 24 L of seawater into a trace metal clean carboy and filtering through either 13 mm quartz or polycarbonate filters. All sample manipulations and filtration took place in a class 100 laminar flow bench. The filters were then later frozen and stored until shipping for later analysis at Rutgers. (ii) Depth resolved sampling was performed using water collected with the NIOZ ultraclean roseefteAl cast. This involved filtering in duplicate 2 L aliquots of seawater through; (1) a sandwiched pair of 13 mm -1.0 pm pore size quartz fiber filter (QMA) and (2) a sandwiched pair of 25 mm 0.45 pm and 50 pm Supor and Poretics plastic filters fibre filters. All filtering was performed with a gentle vacuum over pressure in a Class 100 laminar flow bench. Typically samples were obtained from 25, 50, 100 and 200 m. The filters were then frozen and stored until shipping for later analysis at Rutgers. The collected samples will be analysed by ICP-MS in the laboratory at Rutgers. The present study is an extension of a pilot study examining the feasibility of combining this type of sampling with work on the dissolved metals in the water column carried out by the trace metal group at the lfM- GEOMAR. This is an ongoing international collaboration between Germany and the USA as a contribution to GEOTRACES. Work at sea During ANT-XXIV/3 we collected over 60 samples from along the Greenwich meridian, in the Weddell Sea and through the Drake Passage for particulate metals from the Al casts and from the fish. Preliminary results As analysis of the collected samples is yet to be performed we have no preliminary results at this time. Acknowledgements The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Special thanks to the ultraclean winch team from NIOZ for their help with the sampling. Thanks also to the Chief Scientist, Dr Eberhard Fahrbach and to the AWI Logistics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG (CR145/10) and lfM-GEOMAR. References Berman-Frank, I., Cullen, J.T., Shaked, Y., Sherrell, R.M. and Falkowski, P.G., 2001. Iron availability, cellular iron quotas, and nitrogen fixation in Trichodesmium. Limnology and Oceanography, 46:1249-1260. Cullen, J.T. and Sherrell, R.M., 1999. Techniques for determination of trace metals in small samples of size-fractionated particulate matter: phytoplankton metals off central California. Marine Chemistry, 67: 233- 247. Cullen, J.T., Lane, 1W., Morel, F.M.M. and Sherrell, R.M., 1999. Modulation of cadmium uptake in phytoplankton by seawater CO2 concentration. Nature, 402:165-167. Cullen, J.T., Chase, Z., Coale, K.H., Fitzwater, S.E. and Sherrell, R.M., 2003. Effect of iron limitation on the cadmium to phosphorous ratio of natural phytoplankton assemblages from the Southern Ocean. Limnology and Oceanography, 48: 1079-1087. Field, M.P., Cullen, J.T. and Sherrell, R.M., 1999. Direct determination of 10 trace metals in 50 uL samples of coastal seawater using desolvating micronebulization sector field ICPMS. Journal of Analytical Atomic Spectrometry, 14:1425-1431. Sterner, R.W. et al., 2004. Phosphorus and trace metal limitation of algae and bacteria in Lake Superior. Limnology and Oceanography, 49: 495-507. 3.2.6 The distribution of H202 in surface and deep waters of the Southern Ocean Maija Heller, Katrin Bluhm and Peter Croot IfM-GEOMAR Objectives H202 is a short lived photochemically produced trace oxidant found throughout the water column but predominantly in sunlit surface waters. Information on H202 concentrations allows us to constrain the oxidation time of reduced metal species (e.g. Cu(l), Fe(ll)) in the ocean where H202 can be the principal oxidant, this information is important for understanding the biogeochemical cycling of these metals. Furthermore H202 can be used as a tracer for vertical mixing in surface waters and/or a tracer of recent (last few days) rain or snow events. For ANT-XXIV/3 our objective was to make a synoptic survey of H202 throughout the Atlantic sector of the Southern Ocean and examine the influence of different biogeochemical provinces on its formation and decay. Introduction Hydrogen peroxide (H202) is the most stable intermediate in the four- electron reduction of 02 to H20 and may function as an oxidant or a reductant. H202 is principally produced in the water column by photochemical reactions involving dissolved organic matter (DOM) and 02 (Cooper et al., 1988; Scully et al., 1996; Yocis et al., 2000; Yuan and Shiller, 2001). Open ocean H202 concentrations show a distinct exponential profile with a maximum at the surface consistent with the photochemical flux. Concentrations can reach up to 300 nmol Li in Equatorial and Tropical regions with high DOM concentrations such as in the Amazon plume in the Atlantic (Yuan and Shiller, 2001). In regions with low DOM and low sunlight, surface H202 levels are much lower with values in the Southern Ocean of 10-20 nmol L (Sarthou et al., 1997). Rainwater is a major potential source for H202 to surface seawater as it is preferentially removed from the atmosphere, relative to other peroxides, during convective events (Croot et al., 2004b). Due to its high solubility in water, scavenging of H202 in deep convection is around 55 - 70 % (Cohan et al., 1999). Mixing ratios of H202 in the marine troposphere show a strong latitude dependence with a maximum over the equator, suggesting that the air to surface flux at the equator should be high (Weller and Schrems, 1993). H202 is also produced by biological processes in the ocean with observations from the Sargasso Sea (Palenik and Morel, 1988) and in phytoplankton cultures (Palenik et al., 1987) of production in the dark. Most studies to date have suggested that the major production pathway in the water column for H202 is from photochemical production, however in a few cases in the Southern Ocean, distinct H202 maxima at depth, corresponding to the chlorophyll maximum, suggest a significant biological source of H202 (Croot et al., 2004a). The 'dark decay life- time' of H202 can vary from hours to weeks in the ocean (Petasne and Zika, 1997), but typically may be around 4 days in the open ocean (Plane et al., 1987). Overall the decay rate of H202 is apparently controlled by several factors: H202 concentration, colloid concentration, bacteria/cyanobacteria numbers and temperature (Wong et al., 2003; Yuan and Shiller, 2001). Methods H202 measurements in surface waters Seawater samples were obtained using Niskin bottles on a standard CTD rosette. Samples were drawn into 100 mL low density brown polyethylene bottles which were impervious to light. Samples were analyzed within 1- 2 hours of collection where possible and were not filtered. In the present work H202 was measured using a flow injection chemiluminescence (FIA-CL) reagent injection method (Yuan and Shiller, 1999). In brief, the chemiluminescence of luminol is catalysed by the reaction of H202 present in the sample with Co2 at alkaline pH. H202 standards were made by serial dilution from a primary stock solution (30 % Fluka - Trace Select). The concentration of the primary standard was determined by direct spectrophotometry of the solution (c = 40.9 mol L cm', (Hwang and Dasgupta, 1985)). Secondary standards were analysed with a spectrophotometric method using Cu(II) and 2,9-dimethyl- 1,10phenanthroline (Kosaka et al., 1998). Seawater samples were measured directly by FIA-CL, while rainwaters were diluted, up to 1:100, with ultrapure water (18 MO). Sample concentrations were corrected for a small reagent blank (Yuan and Shiller, 1999). Samples were analyzed using 5 replicates: typical precision was 2-3 % through the concentration range 1-100 nM, the detection limit (3o) was typically 02 nmol Li. Work at sea During ANT-XXIV/3 samples were taken for H202 throughout the water column in connection with the normal Bi hydrocast as part of the IPY GEOTRACES ZERO & DRAKE programme. H202 profiles were measured at 38 stations during the course of ANT-XXIV/3 from a wide range of upper ocean environments (Fig. 3.22). On previous research cruises we have concentrated exclusively on surface waters, however during ANT-XXIV/3 we undertook full depth profiles to examine more closely the concentration of H202 in deep waters. As H202 is a short lived chemical species all sample analysis was performed at sea. Preliminary results Results gathered from ANT-XXIV/3 showed in general surface water concentrations of H202 were relatively low (20 - 40 nM) with one interesting exception in a high productivity region between 65° and 67° S (see Fig. 3.23). Where a major phytoplankton bloom was occurring, in this area H202 concentrations were elevated in the surface waters up to 90 nM which is more typical of values found in Tropical regions. The possible reasons for this include (1) release of large amounts of photolabile DOC by the phytoplankton due to senescence or (2) direct biological production of H202 by phytoplankton cells. Deep water profiles often showed the presence of two distinct regions of elevated H202: at approximately 300 and 1,000 m and it is thought that these may be related to enzymatic reactions associated with the rem ineralization of organic matter that occurs at this depth. Fig. 3.22: The location of stations sampled for H202 during ANT-XXIV/3: (left) Greenwich meridian, (centre) Weddell Sea and (right) Drake Passage. Later work will include comparing the H202 profiles with measurements of other chemical and physical parameter made at each station. Using this approach it should be possible to determine the major processes (e.g. active mixing, rain inputs of H202, production via photolysis or phytoplankton production of H202) controlling the distribution of H202 in both the surface and deep waters in the Southern Ocean along the ANT-XXIV/3 transects. Fig. 3.23: The vertical distribution of H202 from some representative stations during ANT-XXI V/3: top left: Near surface distribution of H202 along the Greenwich meridian in a region impacted by a large phytoplankton bloom. Top right: Full water column profile from the same station. Bottom left: Typical profile for Polar waters not impacted by phytoplankton blooms. Bottom right: H202 profile from the edge of the ice shelf showing the deeper mixing that occurs here. Acknowledgements The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Thanks also to the Chief Scientist, Dr. Eberhard Fahrbach and to the AWI Logistics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG. References Cohan, D.S., M.G. Schultz, D.J. Jacob, B.G. Heikes, and D.R. Blake, Convective injection and photochemical decay of peroxides in the tropical upper troposphere: Methyl iodide as a tracer of marine convection, Journal of Geophysical Research-Atmospheres, 104 (D5), 5717-5724, 1999. Cooper, W.J., R.G. Zika, R.G. Petasne, and J.M.C. Plane, Photochemical Formation of H202 in Natural Waters Exposed to Sunlight, Environmental Science and Technology, 22, 11561160, 1988. Croot, PL., P. Laan, J. Nishioka, V. Strass, B. Cisewski, M. Boye, K. Timmermans, R. Bellerby, L. Goldson, and H.J.W. de Baar, Spatial and Temporal distribution of Fe(II) and H202 during EISENEX, an open ocean mesoscale iron enrichment, submitted to Marine Chemistry, 2004a. Croot, PL., P. Streu, I. Peeken, K. Lochte, and A.R. Baker, Influence of ITCZ on H202 in near surface waters in the equatorial Atlantic Ocean, Geophysical Research Letters (accepted), 2004b. Hwang, H., and P.K. Dasgupta, Thermodynamics of the Hydrogen Peroxide- Water System, Environmental Science and Technology, 19, 255-258, 1985. Kosaka, K., H. Yamada, S. Matsui, S. Echigo, and K. Shishida, Comparison among the methods for hydrogen peroxide measurements to evaluate advanced oxidation processes: Application of a spectrophotometric method using copper(II) ion and 2.9 dimethyl- 1,10-phenanthroline, Environmental Science & Technology, 32 (23), 3821- 3824, 1998. Palenik, B., and F.M.M. Morel, Dark production of H202 in the Sargasso Sea, Limnology and Oceanography, 33, 1606-1611, 1988. Palenik, B., O.C. Zafiriou, and F.M.M. Morel, Hydrogen peroxide production by a marine phytoplankter, Limnology and Oceanography, 32, 1365-1369, 1987. Petasne, R.G., and R.G. Zika, Hydrogen peroxide lifetimes in south Florida coastal and offshore waters, Marine Chemistry, 56 (3-4), 215- 225, 1997. Plane, J.M.C., R.G. Zika, R.C. Zepp, and L.A. Burns, Photochemical modeling applied to natural waters, in Photochemistry of environmental aquatic systems, edited by R.G. Zika, and W.J. Cooper, pp. 215-224, American Chemical Society, Washington D.C., 1987. Sarthou, G., C. Jeandel, L. Brisset, D. Amouroux, T. Besson, and O.F.X. Donard, Fe and H202 distributions in the upper water column in the Indian sector of the Southern Ocean, Earth and Planetary Science Letters, 147, 83-92, 1997. Scully, N.M., D.J. McQueen, D.R.S. Lean, and W.J. Cooper, Hydrogen peroxide formation: The interaction of ultraviolet radiation and dissolved organic carbon in lake waters along a 43-75 degrees N gradient, Limnology and Oceanography, 41(3), 540-548, 1996. Weller, R., and 0. Schrems, H202 in the Marine Troposphere and Seawater of the Atlantic Ocean, Geophysical Research Letters, 20, 125-128, 1993. Wong, G.T.F., W.M. Dunstan, and D.B. Kim, The decomposition of hydrogen peroxide by marine phytoplankton, Oceanologica Acta, 26(2), 191-198, 2003. Yocis, B.H., D.J. Kieber, and K. Mopper, Photochemical production of hydrogen peroxide in Antarctic Waters,, Deep Sea Research Part I : Oceanographic Research, 47(6), 10771099,2000. Yuan, J., and A.M. Shiller, Determination of Subnanomolar Levels of Hydrogen Peroxide in Seawater by Reagent-Injection Chem ilum inescence Detection, Analytical Chemistry, 71, 1975-1980, 1999. Yuan, J., and A.M. Shiller, The distribution of hydrogen peroxide in the southern and central Atlantic ocean, Deep-Sea Research II, 48, 2947-2970, 2001. 3.2.7 Iodide and iodate speciation in the Southern Ocean Katrin Bluhm and Peter Croot IfM-GEOMAR Objectives Iodine is potentially a key element for climate change as iodine emissions from the ocean strongly influence the formation of new aerosol particles with impacts on cloud formation and radiative balances. The source and mechanism of iodine emissions from the ocean is poorly understood, as are other more fundamental aspects of iodine biogeochemistry in seawater such as the cycling between the major iodine species; iodate and iodide. In the proposed work we will investigate the biogeochemistry of iodine in the poorly studied waters of the Southern Ocean. Central to this work will be investigations into the underlying mechanism behind the distribution and speciation of iodine species in the Atlantic sector of the Southern Ocean. During the Polarstern cruise ANT-XXIV/3 ZERO&DRAKE the speciation and distribution of iodine species were examined across gradients of iron concentration and phytoplankton abundance in seawater; ranging from an open ocean region along the prime meridian, the Weddell Sea and Drake Passage and near several Antarctic islands. Introduction Dissolved iodine is ubiquitous and quasi-conservative in seawater and exists predominantly as iodide () and iodate (103), with a total dissolved concentration of about 470 nM (Salinity 35). In fully oxygenated seawater (pH 8.0, pG 12.5) 103 is the thermodynamically stable form of iodine (Wong, 1991). Molecular iodine (12) is only a transient species due to its fast reactivity with organic matter (Truesdale, 1974) and loss to the atmosphere (Leblanc et al., 2006). In surface waters r concentrations reach 50-150 nM, probably through biological reduction of 103 and this occurs to the greatest extent in tropical and subtropical waters (Jickells et al., 1988). In deep waters, below the euphotic zone, iodide decreases to low levels (< 5 nM), while iodate increases to a relatively constant level of about 450 nM. Attempts to explain iodate reduction in the euphotic zone have linked it to phytoplankton growth, microbial respiration (Truesdale and Bailey, 2002), photochemistry (Spokes and Liss, 1996), and sediment- water interactions (Anschutz et al., 2000). The biogeochemistry of iodine in the Southern Ocean is relatively unknown at present with only a single published study from the WeddeD Sea (Campos et al., 1999) which ran along the WOCE A23 transect from the Weddell Sea at 75°S to about 25°S in March-May 1995. In this work Campos et al. (1999) found a systematic increase in iodide in surface waters (0-100 m) from south to north. The lowest values of about 20 nM iodide in surface waters were observed at stations south of the Polar Front. North of the Polar and Subtropical Front values increased up to 100 nM of iodide, where at depth greater than 100 m iodide concentrations dropped down again to less than 20 nM and continue to decrease rapidly with depth until the detection limit of the method (0.08 nM with a precision better than ±5 %). Campos et al. (1999) interpreted their results from north to south as a lower iodide production south of the Polar Front where surface waters contained high nitrate concentrations, a surprisingly similar conclusion to Mclaggart et al. (1994) made for the Tropics, this is however based on the assumption that iodate reduction is related to nitrate reduction via the action of nitrate reductase. They also suggested that the cycling of iodine was different in the various sectors of the Southern Ocean resulting in different nitrate: iodide ratios in the surface waters. Unfortunately Campos et al. had no supporting productivity or chlorophyll data for their work. Truesdale et al. (2003) followed the iodate and total iodine concentrations in a mesocosm experiment in Antarctica. They only found lithe or no change in the iodate concentrations and their results do not support the belief that changes in iodine speciation is only due to phytoplankton growth. These results are somewhat contradictory to laboratory studies made by Wong et al. (2002) and Chance et al. (2007) in which both researchers found a change in iodine speciation during the growth of Antarctic species. Globally iodide production has been suggested as both an indicator of new production (Campos et al., 1996) and of regenerated production (Tian et al., 1996) and the interpretation hinges on whether iodide production is related to nitrate uptake as suggested by Wong (Wong, 2001) or is related to other decomposition processes. It is thus unclear at present exactly what processes control lodate biogeochemistry in the Southern Ocean. The presence of iodide in seawater is a necessary precursory for the production of iodinated organic compounds, many of which are volatile. Iodine chemistry in the atmosphere is also important as iodine released from the ocean is believed to be a major source of new particles to the atmosphere (ODowd et al., 2002) which may alter the radiative forcing in the atmosphere by acting as cloud condensation nuclei. The main flux from the ocean is from the air-sea gas exchange of iodinated organic compounds such as methyl iodide (CH3I) or diodomethane (CH212). These iodinated compounds may be formed in seawater by reactions between organic compounds and iodine species via photolysis reaction (Moore, 2006; Richter and Wallace, 2004) or bacterial action (Amachi et al., 2001; Manley, 2002). Gases such as CH3I and CH212 are relatively short- lived in the atmosphere as sunlight readily breaks the C-I bond producing I radicals (Martino et al., 2006) which form particulate aerosol iodine species (Baker et al., 2000). Thus there has been considerable interest in the flux of methyl iodide from Southern Ocean waters with this area being identified as a major source to the atmosphere (Cox et al., 2005) with large fluxes being observed at the Antarctic Peninsula (Reifenhauser and Heumann, 1992) and more recently in the Weddell Sea (Carpenter et al., 2007). Enhanced production of some iodinated gases was also observed during the recent Southern Ocean iron enrichment experiments: EisenEx (Chuck et al., 2005) and SOFeX (Wingenter et at., 2004). Work at sea Analytical Measurements Seawater samples (unfiltered) were obtained using Niskin bottles on the standard CTD rosette from all depths during the Bi cast of the IPY GEOTRACES ZERO & DRAKE programme. Samples were drawn into 100 mL low density brown polyethylene bottles which were impervious to light. Samples for iodide were analyzed by cathodic stripping square wave voltammetry (Luther et al., 1988), using a pAutolab Ill (Ecochemie) combined with a VA663 electrode (Metrohm), within 3-4 hours of collection. lodate was analyzed by spectrophotometry (Truesdale, 1978; Truesdale and Smith, 1979), by conversion to l3, using 10 cm cells with an Ocean Optics USB4000 spectrophotometer. All analysis was performed under clean conditions in the Class 5 clean room container from the lfM-GEOMAR. Iodide profiles were measured at 30 stations during the course of ANT- XXVI/3 (Fig. 3.24). This included 15 stations on the transect to and along the Greenwich meridian, 2 stations in the coastal waters close to Neumayer, 6 in the Weddell Sea and 7 in the Drake Passage. Sea ice samples were also collected in the coastal waters close to Neumayer, melted and analysed on board. All sample analysis was performed at sea. Preliminary results Iodide concentrations were relatively low (0-40 nM) along the Greenwich meridian, and a typical profile for this region is shown in Fig. 3.25. The highest concentrations for iodide during this cruise were found along the coastal shelf of South America at the end of the transect across the Drake Passage. Initial comparisons with macronutrient data suggest that iodide was weakly related to primary production and that physical mixing appeared to play a strong role in shaping the iodide profile. Of most interest however, was the discovery of elevated iodide at depths below the euphotic layer, which strongly suggests that regeneration processes are responsible for the iodide production at these depths. The iodate data gathered on board also supported this view and indicated that overall iodine was conservative in these waters. Fig. 3.24: The location of stations sampled for iodine speciation (iodide & iodate) during ANT-XXIV/3: (left) Greenwich meridian, (centre) Weddell Sea and (right) Drake Passage Fig. 3.25: A representative profile for iodide in Polar waters from along the Greenwich meridian Acknowledgments The authors would like to show their deep thanks and appreciation to the crew of the Polarstern, for all their efforts in helping us throughout ANT-XXIV/3. Thanks also to the Chief Scientist, Dr Eberhard Fahrbach and to the AWI Logistics Department for making this cruise possible. Funding for participation in this cruise was provided by the DFG and lfM-GEOMAR. References Amachi, S., Kamagata, Y., Kanagawa, 1. and Muramatsu, Y., 2001. Bacteria Mediate Methylation of Iodine in Marine and Terrestrial Environments. AppI. Environ. Microbiol., 67(6): 2718-2722. Anschutz, P., Sundby, B., Lefrancois, L., Luther III, G.W. and Mucci, A., 2000. Interactions between metal oxides and species of nitrogen and iodine in bioturbated marine sediments. Geochimica et Cosmochimica Acta, 64: 2751-2763. Baker, AR., Thompson, D., Campos, M.L.A.M., Parry, S.J. and Jickells, ID., 2000. Iodine concentration and availability in atmospheric aerosol. Atmospheric Environment, 34: 4331-4336. Campos, M., Farrenkopf, AM., Jickells, T.D. and Luther, G.W., 1996. A comparison of dissolved iodine cycling at the Bermuda Atlantic Time- Series station and Hawaii Ocean Time-Series Station. Deep-Sea Research Part li-Topical Studies In Oceanography, 43(23): 455-466. Campos, M., Sanders, R. and Jickells, T., 1999. The dissolved iodate and iodide distribution in the South Atlantic from the Weddell Sea to Brazil. Marine Chemistry, 65(3-4): 167-175. Carpenter, L.J., Wevill, D.J., Palmer, C.J. and Michels, J., 2007. Depth profiles of volatile iodine and bromine-containing halocarbons in coastal Antarctic waters. Marine Chemistry, 103(3-4): 227. Chance, R., Malm, G., Jickells, T. and Baker, AR., 2007. Reduction of iodate to iodide by cold water diatom cultures. Marine Chemistry, 105(1-2): 169-180. Chuck, AL., Turner, S.M. and Liss, P.s., 2005. Oceanic distributions and air-sea fluxes of biogenic halocarbons in the open ocean. Journal Of Geophysical Research-Oceans, 1 10(C10). Cox, ML., Sturrock, GA., Fraser, P.J., Siems, S.T. and Krummel, PB., 2005. Identification of regional sources of methyl bromide and methyl iodide from AGAGE observations at Cape Grim, Tasmania. Journal Of Atmospheric Chemistry, 50(1): 59-77. Jickells, ID., Boyd, 5.5. and Knap, AH., 1988. Iodine Cycling in the Sargasso Sea and the Bermuda Inshore Waters. Marine Chemistry, 24: 61- 82. Leblanc, C. et al., 2006. Iodine transfers in the coastal marine environment: the key role of brown algae and of their vanadium- dependent haloperoxidases. Biochimie, 88(11): 17731785. Luther, G.W., Swartz, C.B. and UlIman, W.J., 1988. Direct determination of Iodide in Seawater by Cathodic Stripping Square Wave Voltammetry. Analytical Chemistry, 60: 1721-1724. Manley, S.L., 2002. Phytogenesis of halomethanes: A product of selection or a metabolic accident? Biogeochemistry, 60(2): 163-180. Martino, M., Liss, P.S. and Plane, J.M.C., 2006. Wavelength-dependence of the photolysis of diiodomethane in seawater. Geophysical Research Letters, 33(6). Mclaggart, AR., Butler, E.C.V., Haddad, P.R. and Middleton, J.H., 1994. Iodide And lodate Concentrations In Eastern Australian Subtropical Waters, With Iodide By Ion Chromatography. Marine Chemistry, 47(2): 159-172. Moore, R.M., 2006. Methyl halide production and loss rates in sea water from field incubation experiments. Marine Chemistry, 101(3-4): 213. O'Dowd, C.D. et al., 2002. Marine aerosol formation from biogenic iodine emissions. Nature, 417: 632-636. Reifenhauser, W. and Heumann, KG., 1992. Determinations Of Methyl- Iodide In The Antarctic Atmosphere And The South Polar Sea. Atmospheric Environment Part AGeneral Topics, 26(16): 2905-2912. Richter, U. and Wallace, D.W.R., 2004. Production of methyl iodide in the tropical Atlantic Ocean. Geophysical Research Letters, 31(23). Spokes, L.J. and Liss, P.S., 1996. Photochemically induced redox reactions in seawater.2. Nitrogen and iodine. Marine Chemistry, 54(1-2): 1-10. Tian, R.C. et al., 1996. Iodine speciation: A potential indicator to evaluate new production versus regenerated production. Deep-Sea Research Part I-Oceanographic Research Papers, 43(5): 723-738. Truesdale, V.W., 1974. The chemical reduction of molecular iodine in seawater. Deep Sea Research and Oceanographic Abstracts, 21(9): 761. Truesdale, V.W., 1978. The Automatic Determination of lodate and Total- Iodine in Seawater. Marine Chemistry, 6: 253-273. Truesdale, V.W. and Bailey, G.W., 2002. Iodine distribution in the Southern Benguela system during an upwelling episode. Continental Shelf Research, 22(1): 39-49. Truesdale, V.W., Kennedy, H., Agusti, S. and Waite, T.J., 2003. On the relative constancy of iodate and total-iodine concentrations accompanying phytoplan kton blooms initiated in mesocosm experiments in Antarctica. Limnology And Oceanography, 48(4): 1569-1574. Truesdale, V.W. and Smith, C.J., 1979. A Comparative Study of Three Methods for the Determination of lodate in Seawater. Marine Chemistry, 7: 133-139. Wingenter, OW. et al., 2004. Changing concentrations of CO, CH4, C5H8, CH3Br,CH3I, and dimethyl sulfide during the southern ocean iron enrichment experiments. Proceedings Of The National Academy Of Sciences Of The United States Of America, 101(23): 85378541. Wang, G.T., Piumsamboon, A.U. and Dunstan, W.M., 2002. The transformation of iodate to iodide in marine phytoplankton cultures. Marine Ecology Progress Series, 237: 27-39. Wang, G.T.F., 1991. The Marine Geochemistry Of Iodine. Reviews In Aquatic Sciences, 4(1): 45-73. Wong, G.T.F., 2001. Coupling iodine speciation to primary, regenerated or 'new' production: a re-evaluation. Deep-Sea Research Part I- Oceanographic Research Papers, 48(6): 1459-1476. 3.2.8 Measurements of AOT (Aerosol Optical Thickness) over the Southern Ocean Peter Croot and Maija Heller, IfM-GEOMAR not on board: A. Smirnav, NASA/Goddard Space Flight Center Objectives There is a currently a lack of ground truth information for measurements of AOT (Aerosol Optical Thickness) from the Southern Ocean. While satellite measurements of AOT are possible at present through a number of dedicated satellites (MODIS AQUA and TERRA) data interpretation is reduced due to persistent cloud cover and reflections from sea ice and waves. Direct measurements of AOT from the surface using the sun as a light source are possible using small handheld devices such as the MICROTOPS and provide a useful dataset to validate retrieval algorithms for satellite estimation of AOT as well as providing instantaneous information for shipboard users. For ANT-XXIV/3 we undertook measurements of AOT when the weather permitted to provide baseline data for improving satellite retrievals and for assessment of any contribution from Patagonian dust to the aerosol loading over the Southern Ocean. Transport of airborne dust from the continents provides a route by which Fe and other trace elements can enter remote surface ocean waters. This transport can be of particular importance for supplying iron to HNLC regions where Fe is the limiting nutrient. For the Atlantic sector of the Southern Ocean and the Weddell Sea it is suspected that much of the iron supplied to surface waters originates from Patagonia but the supply is extremely episodic (Erickson Iii et al. 2003; Gaiero et al. 2004; Gasso and Stein 2007). Work at sea During ANT-XXIV/3 discrete AOT measurements were made using a MICROTOPS II kindly loaned by the NASA/Goddard Space Flight Centre as part of the AERONET Maritime Aerosol Network programme (http :llaeronet. gsfc. nasa. gov/new_web/mariti me_aerosol_network. html). The MICROTOPS Ills a handheld instrument that is well characterised for AOT measurements (Ichoku et al. 2002) and is capable of being used on moving platform such as a ship at sea (Porter et al. 2001), though the data does require some corrections because of ship movement (Knobelspeisse et al. 2003). Over 1400 individual measurements were collected during the course of ANT-XXIV/3 corresponding to the periods when the sun was visible and not obscured by clouds. Problems were encountered with rough sea states and high winds but in general observations were easily made. Preliminary results The preliminary data indicated extremely low AOT over the course track most of the time suggesting there was little dust encountered during the cruise as might be expected for this remote region. Slightly elevated AOT was found along the Greenwich meridian at the location of the phytoplankton bloom and this may be due to increased biogenic aerosol production during the bloom though this must be confirmed by later comparison with satellite data collected at the same time. Further Satellite data relayed to us during the cruise (Santiago Gasso - NASA) indicated that there were some minor dust events from Patagonia occurring during the duration of ANT-XXIV/3 but back trajectories indicated a mostly easterly course which did not intersect with the ships position at any time. The collected AOT data will be further processed before release to the web. References Erickson Iii, D. J., J. L. Hernandez, P. Ginoux, W. W. Gregg, C. Mcclain, and J. Christian. 2003. Atmospheric iron delivery and surface ocean biological activity in the Southern Ocean and Patagonian region. Geophysical Research Letters 30: 1609, doi:1 610.1 02912003GL01 7241. Gaiero, D. M., P. J. Depetris, J. L. Probst, S. M. Bidart, and L. Leleyter. 2004. The signature of river- and wind-borne materials exported from Patagonia to the southern latitudes: a view from REEs and implications for paleoclimatic interpretations. Earth And Planetary Science Letters 219: 357-376. Gasso, S., and A. F. Stein. 2007. Does dust from Patagonia reach the sub-Antarctic Atlantic Ocean? Geophysical Research Letters: L01801, doi :01810.01 029/02006G L027693. Ichoku, C. and others. 2002. Analysis of the performance characteristics of the five-channel Microtops II Sun photometer for measuring aerosol optical thickness and precipitable water vapor. Journal of Geophysical Research 107: 4179, doi:4110.1029/2001JD001302. Knobelspeisse, K. D., C. Pietras, and G. S. Fargion. 2003. Sun- Pointing-Error Correction for Sea Deployment of the MICROTOPS II Handheld Sun Photometer. Journal of Atmospheric and Oceanic Technology 20: 767-771. Porter, J. N., M. Miller, C. Pietras, and C. Motell. 2001. Ship-Based Sun Photometer Measurements Using Microtops Sun Photometers. Journal of Atmospheric and Oceanic Technology 18: 765-774. 3.3 ISOTOPES BY THE AWI-TEAM Ingrid Stimac(1), Celia Venchiarutti1, (1)Alfred -Wegener-Institut Maya Robert(1), Pinghe Cai(3), (2)IFM-GEOMAR Torben Stichel(2), Elizabeth Sweet(1). (3)Xiamen University, China Not on board: Michiel Rutgers van der Loeff(1) Martin Frank 2) Michael Staubwasser (Univ. Cologne), Christina de la Rocha(1), Dieter Wolf-Gladrow(1) Background and general objectives Uranium-series radionuclides are powerful tracers for the rate of transport processes in the ocean. We wish to measure the distribution of U-series isotopes along the Greenwich meridian and in the Drake Passage. The sampling will be coordinated with sampling of other trace elements. This joint sampling allows us to directly apply the information on particle dynamics (aggregation, disaggregation and particle sinking rates) and terrigenous input that we will obtain from the distribution of thorium isotopes and 231Pa, to the transport of other tracers. Similarly, we will be able to confront the results on water mass ventilation and upwelling, as we will derive from 230Th/231Pa and 227 Ac distributions, with hydrographic data and the conclusions drawn from other tracers described in parallel proposals (Nd/Hf isotopes; freons). The data will be interpreted along with other tracer data in (inverse) GCM models. We expect that this approach will improve our ability to use a set of tracers as more reliable proxies for past ocean climate. 3.3.1 234Th as tracer of export production of POC Ingrid Stimac(1), Pinghe Cai(2), (1)Alfred-Wegener-Institut Michiel Rutgers van der Loeff(1) (2)Xiamen University, China Objectives The objectives of the project are: 1) to acquire accurate estimates of upper ocean POC export fluxes in the Southern Ocean; 2) to infer the export fluxes of some particle-reactive elements/compounds (i.e., Fe, Al, Mn, Cu, Cd, Ni, Zn, and Ag) that will be measured by other researchers in the same regions (see section on trace metals above; and 3) to carry out the intercomparison of POC export studies between 234Th/238U and 210Po/210Pb methods. Work at sea 1) A total of 20 depth profiles of total 234Th in 4-L water samples have been collected with the CTD. 2) Deployment of in-situ pumps in order to obtain size-fractionated samples of suspended particles and determine the POC/234Th ratio in those size fractions. In parallel to the sampling in Rosette casts we have used our automated 234Th analyser to obtain the distribution of particulate and dissolved 234Th in the surface water at higher spatial resolution. Samples were drawn every 4 hours from the ships seawater supply. The distribution of particulate 234Th gave a consistent picture. We have the experience that particulate 234Th is an indirect representation of the suspended load in seawater. Plankton blooms are e.g. usually reflected in an increase of particulate 234Th As we approached the shelf ice a prominent drop in particulate 234Th showed the presence of very clear water. The automated analysis of dissolved 234Th involves a coprecipitation of Th with Mn02. The efficiency of this coprecipitation has been monitored by a continuous intercalibration programme with the manual 4-L method described above. The results of this programme will only be available after the measurement of a 230Th yield tracer at AWL Dissolved and total 234Th data from the automated analysis were therefore not yet available on board. Preliminary results The depth profiles of total 234Th show that 234Th deficit varied substantially over the upper Southern Ocean (Fig. 326). This indicates remarkable variations in POC export in the Southern Ocean. Fig. 3.26: Depth profiles of total 234That Station 101, 118 and 178 in the Southern Ocean. Note that the recovery for 234 Th is yet to be determined. 3.3.2 Analysis of multiple thorium isotopes and 231pa Ingrid Stimac(1), Celia Venchiarutti(1), (1)Alfred-Wegener-Institut Pinghe Cai (2), Michiel Rutgers van der (2)Xiamen University, China Loeff(1) Objectives 230Th and 231Pa are both the decay products of soluble and conservatively distributed uranium isotopes (234U and 235U). Th and Pa are produced at a fixed known rate in the ocean and are both sensitive to scavenging. The distributions of 231Pa and 230Th are controlled by particle flux and boundary scavenging. Thus, changes in the water column distribution of these isotopes can be interpreted as indication of changes in water mass ventilation and in particle flux. If no scavenging and/or recent ventilation of water masses occurs, the production rate of Th and Pa along the water column is constant, resulting in a distribution that increases with increasing depth. With a residence time of 50 to 100 years, 230Th is more reactive than 231Pa (residence time in seawater of approximately 200 years) and will trace more rapid and recent processes. We wish to determine 231Pa and 230Th in filtered seawater and suspended particulate matter along the Greenwich meridian and in the Drake Passage. The distribution of multiple Th isotopes over particulate and dissolved phase can be used to derive adsorption and desorption rates. When the particles are separated according to grain size before analysis (e.g. with a 50 µ screen), then the isotopes can be used to constrain the settling velocity of small and large particles in the upper 1000 m of the water column. If the distribution of Th isotopes is obtained over various size fractions it is possible to derive aggregation and disaggregation rates. Work at sea Dissolved 231Pa and 230Th analysis requires collection of 20 L of filtered (<1 pm) seawater. The 20 L are collecting using the Niskin bottles into acid-cleaned collapsible cubitainers, filtered through a 142 mm diameter Supor(r)-450 filter of 0.45 µm pore size (Pall). Then, all seawater samples are stored acidified (with concentrated distilled HNO3), without addition of any tracers. The Supor(r)-450 filters are stored wet in special plastic bags and stored at 4°C. All the samples will be further processed at the home laboratory (addition of the tracers, coprecipitation, chromatographic extraction and spectrometric measurements). About 8-11 samples are collected at each super station, giving a full water column profile with a good resolution. Therefore, 13 profiles were realised, 6 along the Greenwich meridian (Fig. 3.27) 2 in the Weddell Sea (Tab. 3.2) and 5 at Drake Passage. At some stations, duplicates were achieved. Thus, in the scope of GEOTRACES intercalibration and the BONUS-GOODHOPE expedition, 3 duplicates were collected at Station 113 (20/02/08, at 1,000 m, 500 m and 380 m for the 231Pa and 230Th analysis that will be achieved at LEGOS in Toulouse (Catherine Jeandel and Matthieu Roy-Barman). Three duplicates were also collected at the same location (on 12/03/08 at 52°59'S and 0°0'E) by the BONUS-GOODHOPE expedition. An extra station was realised near the ice shelf at 70°34'S and 8°7'E on 5/03/08. Surface samples were collected with the IFISH and filtered like the other samples on Supor(r)-450 filters. Tab. 3.2: List of all the 20 L samples collected for the Nd, Th and Pa analysis at the different stations with the indicated depths (from 10 Feb. 08 to 16 Apr. 08). Values followed by an "@" are depths that need to be checked for precision, by a "#" are the duplicated samples for the GEOTRACES intercomparison and a "*", the duplicated depth/samples. 11/02/2008 13/02/2008 13/02/2008 17/02/2008 20/02/2008 24/02/2008 05/03/2008 09/03/2008 12/03/2008 Test stn Test stn 4513m 2189m 2462m 4177m 131m 4487m 1961m Stn 97 Stn 99 Stn 101 Stn 104 Stn 113 Stn 131 Stn 154 Stn 161 Stn 178 100@ 2000 Bottom-100 Bottom-100 Bottom-100 Bottom-100 Bottom Bottom-100 Bottom 1000 3000 2500 1500 3800 10 3400 1500 2000 2000 1000 3000 2400 1000* 1000 1250 1000# 2000 1200 800 750 750 750 1000 800 500* 500 500 500 500 440 200 200 200 500# 250 200 100* 75 75 380 100 100 50 surface 380# surface 150 surface 70 surface duplicates* 18/03/2008 29/03/2008 2-3/04/2008 5/04/2008 7/04/2008 9/04/2009 11/04/2010 4897m 380m@ 3475m 3785m 3490m 3999m 3800m Stn 193 Stn 222 Stn 230 Stn 236 Stn 241 Stn 244 Stn 250 Bottom Bottom Bottom Bottom Bottom Bottom Bottom 4000 280 3000 2800 2800 3500 3000 3200 180 2500 1750 2000 3000 2200 2200 100 2000 1000 1250 2500 1600 1200 50 1500 400 750 1750 900 800 1000 250 480 1250 500 500 500 120 150 750 300 200 400 50 50 500 150 50 250 200* 150 75 50 25 duplicates* So far, 119 samples were collected for the dissolved 231Pa and 230Th analysis. 13 super stations have been realised, 2 test stations, a small station close to the Antarctic ice shelf and some surface samples collected from the IFISH. Fig. 3.27: Sampling location and depths along the Greenwich meridian Particulate Due to the 231Pa and 230Th low concentrations in particles (10 times less than in the dissolved phase), their analysis requires large volumes of filtered seawater of about 500-1,000 L. Size-fractionated particulate material sampling was achieved, using 6 "Challenger" in-situ pumps. The filter holders of these pumps are set up with a stack of 3 different filters of 142 mm diameter and separated by grids. The lower filter is a Supor(r)-800 filter (Pall) of 0.80 pm pore size on which the small particle fraction (0.8 - 10 μm) is collected. Then, above the Supor(r)- 800, a Nitex filter of 10 pm pore size is mounted and will allow the recovery of the intermediate size particles. Another Nitex filter of 50 pm pore size is added on the upper part to collect the large particle fraction. This size- fractionated particulate study is always achieved at 100 m depth for the on board 234Th analysis with beta counting. Then, 5 other samples are collected for 231Pa and 230Th analysis at different depths so as to get a full water column profile. The on-board 234Th analysis was further extended during the cruise to other depths of the profile, so as to combine both information on the export with 234Th and 230Th. The 231Pa, 230Th and 232Th analysis in the 3 size- fractionated particles requiring clean-lab chemistry and high resolution mass spectrometry measurements will be realised at the home laboratory. The pumping time is ca. 3 hours for most of the deep stations and the entire procedure (deployment and recovery) ranges from 5 to 7 hours. In 3 hours about 400 - 500 L of seawater were typically filtered at very high particle flux stations and between 600-800 L at stations with lower biological productivity. Briefly, once collected on the Nitex filters, the size-fractionated particulate material (50 and 10 pm) was recovered by sonication (leaching in ultrasonic bath with 100 - 200 ml of 0,2 pm filtered bottom seawater) and the resulting solution filtered through a 47 mm Supor(r)-450 filter. The 47 mm filters, representing both size-fractionated particles (50 and 10-50 µm), were then stored in clean petri dishes. If any sample has to be counted for 234Th, the 47 mm was dried at 50°C in the oven and then folded in order to be measured with beta counting. Otherwise they were stored wet in the fridge at 4°C. In this latter case, a part of the Supor(r)-800 filter (small particles) was cut under clean conditions (flow hood in clean container, cleaned material) and punched (with a 22 mm diameter punch) to enable a 234Th counting for the small fraction size particles. The other part of the Supor(r)-800 filter was folded in half and stored in special plastic bags at 4° C. Tab. 3.3 sums up the particulate sampling, realised with the ISP, during the expedition. For stations 131, 161 and 178, the 234Th was counted on the large and intermediate size-fractionated particles. At stations 193, 222 (Weddell Sea), 230 and 241 (Drake Passage), a part of the Supor(r)-800 filters was cut and punched to allow 234Th beta counting for the small particle fraction as well. Therefore, at these 4 stations, a full particulate 234Th profile was achieved. The major part of the filters was then stored in the special plastic bag and frozen. Tab. 3.3: Summary of the size-fractionated particulate samples (50 µm, 10 µm and 0.8 µm) collected with the in-situ pumps from 10.02.08 to 16.04.08. Highlighted in green the 100 m sample for Pinghe Cai. The low filtered volumes (when pumping did not work well) are noted in red*. Depth (m) Volume (L) Depth (m) Volume (L) Depth (m) Volume (L) Depth (m) Volume (L) ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- 13/02/2008 17/02/2008 20/02/2008 24/02/2008 Stn 101 Stn 104 Stn 113 Stn 131 l00 did not work 100 2831 100 1731 100 2406 200 358 200 did not work 50 282 250 719 500 494 500 631 200 453 500 658 750 537 750 1932 500 547 1000 666 1000 90* 1250 79* 750 374 2000 1278 2000 524 2500 517 1000 1352 3800 634 09/03/2008 11/03/2008 18/03/2008 Stn 161 Stn 178 Stn 193 Stn 222 100 953 100 762 100 840 100 532 200 416 200 354 200 409 180 271 440 419 500 1123 500 482 280 481 1200 596 800 445 1200 631 380 281 2400 450 1000 321 3200 182* 3400 568 1500 425 bottom 503 02/04/2008 05/04/2008 07/04/2008 07/04/2008 Stn 230 Stn 236 Stn 241 Stn 244 100 733 100 584 100 336 100 160* 250 1251 250 1392 120 162* 200 325 500 417 400 386 750 421 750 499 1000 636 1000 644 1250 634 1250 702 2000 440 2800 279 2800 1551 2400 663 3000 483 3500 397 3300 413 3500 391 11/04/2008 Station 250 100 378 150 222 500 382 900 606 2200 466 3700 368 Sediment Activities stored in marine sediments can help to reconstruct particle flux patterns in the past and surface sediments to evaluate patterns of particle flux and boundary scavenging. Therefore, it is a required complementary study to investigate the particle dynamics and the winnowing and focusing processes occurring on the seafloor in an area submitted to strong currents as the Drake Passage. In this frame, sediment cores were collected with the minicorer (Fig. 3.28) at three super stations in the Drake Passage (241, 244 and 250). The minicorer was deployed under the normal AWI CTD, 20 m below the CTD frame. The altimeter signal gave an estimate of the moment when the minicorer had reached the bottom. Enough sediment cores were obtained with the minicorer at Station 241 and were sliced and stored in plastic containers. At first sight, it seems that this sediment was constituted of clays or silts, with a sandy aspect and overlied by numerous Mn crusts (Fig. 3.29). Fig. 3.28: Minicorer deployment during ANT-XXIV/3 Fig. 3.29: Mn crust at station 241 Further analyses In the vicinity of the Antarctic Peninsula, Ra samples, 228Th and further 227Ac samples were included in the analyses. Preliminary results There are no preliminary results for the 231Pa and 230Th analysis since it requires clean-room work and further processes such as mass spectrometric techniques that cannot be realised on board and will be done back at the home laboratory. However, the 234Th counting on the particles was achieved on board. Thus, Figures 3.30 and 3.31 represent the coarse profiles obtained for the 234Th for the large and intermediate size particles at stations 131, 161 and 178 and for the total particulate phase at stations 193, 222, 230 and 241. On Fig. 330, even without the small fraction size particle measurement, a "normal" 234Th pattern can be clearly noticed with decreasing particulate 234Th with depth at most of the stations, except the maximum observed at station 178 at 1000 m. Close to the bottom, at stations 222 and 230, the particulate 234Th, as expected, increases, likely due to sediment re-suspension. Moreover, the range of the 234Th particulate concentrations in both fractions is in agreement with what can be expected (personal comm. Pinghe Cai) confirming that the sonication step efficiently worked. Fig. 3.31 displays the total particulate 234Th at 4 stations: 193 and 222 in the Weddell Sea, 230 and 241 in the Drake Passage. On most of these profiles, the characteristic trend of the particulate 234Th can be seen with higher concentrations at the surface and near the bottom. To the exception of some surface values, all along the water column, the mean total particulate 234Th concentrations are ca. 0.05 dpm/L. The maximum values are found at the surface and for the station 222 near the Antarctic Peninsula where the profile follows once more the general pattern with a high value near the surface, decreasing with depth and increasing again close to the seafloor. Fig. 3.30: 234Th concentrations (in dpm/L) in 10 and 50 pm combined particle fractions, i.e. for particles >10 pm. The error bars represent a 10 % error on the final value. Fig. 3.31: Total particulate 234Th concentrations (in dpm/L) in all 3 size fractions (L e. particles > 0.8 gm). The error bars represent a 10 % error on the final value. 3.3.3 Importance of marine polysaccharides for radionuclides cycling Maya Robert Alfred-Wegener-Institut not on board: J. Friedrich, Alfred-Wegener-Institut Background Dissolved organic matter (DOM) forms the largest pool of material in the marine environment. The colloidal fraction of the DOM is highly reactive and thus, plays a large role in biological, physical and chemical processes. Due to their high molecular weight, polysaccharides belong to the colloidal organic matter (COM). These substances are mainly released by marine phytoplankton and bacteria. Some of these exopolymers can abiotically aggregate to form particles called transparent exopolymer particles (TEP). TEP are very sticky and consequently a key controlling factor in vertical fluxes as they glue together diverse particles. This occurs via aggregation and leads to the formation of large marine aggregates. The sticky nature of TEP is linked to the presence of a high fraction of acidic polysaccharides with sulphate ester groups, which give the ability to form cations bridges and hydrogen bounds, especially with trace elements. Thorium-234 (234Th), lead-210 (210Pb) and polonium-210 (210Po) are produced by radioactive decay of uranium-238 in seawater. 234Th (24 days half life), 210Po (138 days half life) and 210Pb (22.3 years half life) are known for their high affinities to particles and aggregates. In seawater these radionuclides occur both in dissolved form and adsorbed onto particles. In the COM pool, the polonium (P0) distribution differs from thorium (Th) and lead (Pb). Whereas Th and Pb seem to have a higher partitioning coefficient in polysaccharide- enriched COM than in the bulk COM, Po seems to have a much higher partitioning coefficient in bulk COM than in polysaccharide-enriched COM. This selective complexation points out the importance of the chemical composition of marine particles in controlling the scavenging of particle reactive radionuclides in particular and trace elements in general in the ocean. Objectives During the GEOTRACES activities of ANT-XXIV/3 we want to: 1) get a better insight into binding affinities of Th, Pb and Po for polysaccharide-like particles and protein-like particles. 2) Investigate to which extend TEP can play a role in extending 210Po as a proxy for particulate organic carbon (POC) transport. Work at sea 1) At the superstations 210Po and 210Pb have been sampled at different depths in the water column (25, 100, 200, 500, 750, 1000 m) on the three transects (from CTD rosette Niskin bottles) in 30-40 L samples for particulate and dissolved fractions (over 1pm and truly dissolved respectively). Additional samples (10-20 L) were used to determine the concentrations of TEP and protein-like particles (CSP) in the particulate and dissolved fractions (filtration over 1 µm then through 0.4 µm respectively). POC has also been sampled at each depth studied (filtration onto precombusted GF/F filters). The filters retaining the particulate phase for the radionuclides have been measured on board in order to determine the 234Th/238U ratio. Back at the AWI, the same filters will be analyzed for 210Pb/210Po determination. So far, 7 depths profiles can have been sampled. 2) Whenever high volumes of water (ca. 100 L from the chlorophyll maximum depth) have been available from the CTD, aggregation experiments have been conducted. After determination of the same parameters as described above, the seawater is incubated in 5 L container that are maintained in rotation (3 rpm) in the dark, at 2°C, for different time scale (from 24 h up to 15 days). These experiments aim at monitoring the transfer of radionuclides (234Th, 210Po, 210Pb) between the dissolved and he particulate fractions and try to correlate these changes to those that could be observed for POC, DOC, TEP and /or CSP. So far, 3 aggregation experiments have been conducted. Preliminary results All the samples will be later analyzed either in the Geochemie or the Biogeochemie groups of the AWL In Fig. 3.32, the 234Th profiles show different 234Th deficit patterns. Fig. 3.32: Profile of 234Th in the particulate phase (over 1um) for the 200 upper meters N.B.: Errors bars have not been calculated yet. The error can vary from ca. 5 to 10%. 3.3.4 Radium isotopes and 227 Ac Ingrid Stimac Alfred-Wegener-Institut not on board: M. Rutgers van der Loeff, C. Hanf land Alfred-Wegener-Institut Objectives Four radium isotopes are supplied to the ocean by contact with the continent or (deep-sea)-sediments: 223 Ra, (half-life 11.4 d) ; 224 Ra (3.7 d), 226 Ra (1620 y) and 228 Ra(5.8 y). The distribution of these isotopes in seawater has been shown to be most helpful to evaluate shelf-basin exchange and water residence times. On the Greenwich meridian we expected extremely low concentrations of all but the longlived 226 Ra. We have concentrated the Radium sampling programme in the area around the Antarctic Peninsula where Ra isotopes are most informative on shelfwater interaction (Hanfland, PhD thesis 2002; Dulaiova, pers. comm.). Like Ra isotopes, 227 Ac is released from sea sediments, but its main source is in deep-sea sediments. This tracer is therefore especially useful to study deep water mixing and ventilation. Work at sea Radium During 13 deployments of in-situ pumps a set of two MnO2 -coated polypropylene fiber cartridges was used to adsorb dissolved radionuclides. (On station 279 loose MnO2-fiber was used instead to allow immediate measurement of 224 Ra with the RaDeCC system, but the adsorption efficiency turned out to be unsatisfactory). The 228Ra/226Ra isotope ratio will be quantified in the home laboratory by Soxhlet acid leaching and subsequent gamma spectroscopy; 226 Ra will be derived from the relationship established on earlier expeditions between 226 Ra and dissolved silicate. For the analysis of short-lived radium isotopes, surface water from the ship's seawater intake was cartridge-filtered at 31 stations and transferred into 250 L tanks in the fishlab. At four shelf stations (154, 155, 216, and 221) additional 60-L subsurface samples were collected with the Rosette and treated similarly. Each sample was pumped at max.1 L/min through Mn02-impregnated acrylic fiber to scavenge radium isotopes. Fibers were dried using compressed air, and short-lived 223 Ra and 224 Ra measured at-sea using RaDeCC detectors. Actinium 227 Ac has been sampled in two ways. First, it is collected along with radium on the Mn02-coated cartridges during in-situ pump deployments. Due to the absence of a second isotope that could serve as yield tracer to correct for insufficient absorption of Ac on the fiber, this procedure leaves an appreciable uncertainty. The second procedure used the discrete approx. 60-L samples from Rosette casts collected in cooperation with Torben Stichel for the combined analysis of Hf isotopes and 227 Ac (see section on Nd and Hf isotopes). Samples were filtered and Hf and Ac were coprecipitated with Fe(OH)3. After return to Germany these samples will be separated with ion-exchange procedures and analysed in the Kiel and Bremerhaven labs. Expected Results From the analysis of radium isotopes we expect to derive signals of shelf input which can be related to parallel studies on trace metals (Mn, Al: Rob Middag; Fe: Maarten Kiunder) and 232Th (Celia Venchiarufti). The 227 Ac data will enlarge the very sparse dataset of this isotope. After correction for activity that is supported by production from 231Pa in the water column (from the study of Celia Venchiarutti) the excess concentrations (227 Ac) will be used to estimate upwelling rates of deep water. 3.3.5 Neodymium (Nd) and hafnium (Hf) isotopes Torben Stichel IFM-GEOMAR not on board: M. Frank, IFM-GEOMAR Objectives The subject of our study is a detailed investigation of the distribution of neodymium (Nd) and hafnium (Hf) isotopes in dissolved and particulate form in the water column and in the seawater-derived fraction of surface sediments of the Atlantic sector of the Southern Ocean. Nd isotopes have been shown to be a powerful geochemical tracer for present and past water mass mixing and source provenance tracing in the ocean. The combination with Hf isotopes was applied successfully for the characterization of continental weathering regimes, i.e. it has been suggested that coupled Nd-Hf isotope analyses of Hf and Nd allow to distinguish weathering regimes dominated by chemical weathering from those dominated by physical weathering (van de Flierdt et al., 2002). Both isotope systems have been used for the reconstruction of water masses in the Southern Ocean on various time scales in the past from marine sediments. So far there are, however, nearly no data for the water column of the Southern Ocean, which severely restricts the reliable application of this combination of tracers for present day studies and reconstructions of the past. In the frame of the international GEOTRACES programme we collected large volume water samples from the surface ocean and from depth profiles at selected stations during ANTXXIV/3. Work at sea Greenwich meridian On the Greenwich meridian we have collected 25 samples (8 surface samples taken with the towed fish and 17 deep samples by the CTD rosette; Tab. 34) with a total volume of about 1500 liters for Nd and Hf isotope measurements. The samples were collected under trace metal free conditions in acid cleaned 20 liter holding collapsible cubitainers. The Hf concentration in seawater ranges from 02 to 1 pmol/kg and is thus very low (Godfrey et al., 1996; McKelvey and Orians, 1998). For meaningful Hf isotope measurements on a multi collector inductively coupled mass spectrometer (MC-ICPMS) in the home laboratory, Hf from at least 50-60 liters (5-10 nanograms Hf) were needed for each sample taken below 100-200 meter. Due to the even lower Hf concentration in the surface waters, samples taken by the towed fish, had to be even larger (100-120 liters). After collection, the samples were filtered through a filter of 0.45 pm mesh width, which was kept for later particle analysis. In order to avoid adsorption of Nd and Hf onto the walls of the cubitainers, the samples were acidified to pH 2 by addition of double distilled concentrated acid. For every large volume sample we filtered, acidified, and stored a 2 liter aliquot to determine the concentration of Nd and Hf by isotope dilution in the home lab. To the rest of each sample 05 ml of a FeCI3 solution containing 200 mg Fe per ml were added to each 20 liter sample. After this step the pH was titrated back to 7-8 by addition of a suprapure ammonia solution to co-precipitate FeOOH, which scavenged the dissolved trace metals in the sample. After 24-48 h most of the supernatant was discarded. Afterwards the samples were transferred into 2 liter acid cleaned wide mouth bottles. Additionally, at each Super Station shared 20 liter samples were taken for Nd, thorium (Th), and protactinium (Pa) isotope measurements (see subsection 3.32) to have a total of 59 Nd samples inclusive duplicates. Tab. 3.4: List of samples from hydro-casts (a) and surface waters (b) with corresponding depths in meters for each station. a) Stat.: 71/101 71/104 71/131 71/161 71/181 LAT: 42°20.3'S 47°39.3'S 58°59'S 66°30'S 69°36'S LONG: 8°59.6'E 4°16.2'E 0°E 0°E 0°E --------------------------------------------------------------- 750 400 400 440 1465 750 900 800 1200 1500 1200 2000 2500 2400 4500 4070 3400 b) Stat: I II 71/105 71/116 71/133 LAT: 34°53.1'S 38°38'S 47°39.3'S 54°21'S 59°14.4'S LONG: 16°40.7'E 11°35.8'E 4°16.16'E 0°01'E 0°02.9'E b) continued Stat: 71/142 71/151 GvN-Fish 71/156 LAT: 62°20'S 65°19'S 68°31.8'S 67°08'S LONG: 0°E 0°E 4°39'W 0°24'E Weddell Sea and Drake Passage On the transect from Neumayer Station (Atka Bay, Antarctica) to Punta Arenas (Chile) a total of 39 water samples for Hf and Nd analyses were collected in the Weddell Sea and the Drake Passage. 12 of these samples were taken from surface waters and 27 samples from hydro cast CTD profiles (Tab. 3.5). In addition, 50 shared samples in total were taken for Nd, Th and Pa isotope measurements on all Super Stations (see subsection 3.32). Tab. 3.5: List of samples from hydro-casts (a) and surface samples (b) recovered in the Weddell Sea and the Drake Passage with corresponding depths in meters. a) Stat.: 71/193 71/222 71/236 71/241 71/250 LAT: 66°36'S 63°21'S 59°00'S 57°38'S 55°45'S LONG: 27°17'W 52°51'W 58°09'W 60°53'W 64°26'W ---------------------------------------------------------------- 500 450 500 480 500 1200 1000 750 900 2200 1500 1250 1600 3200 2500 2800 2500 4800 3700 3550 3800 b) Stat.: III 71/186 71/191 IV V VI LAT: 60°02'S 69°03'S 67°21'S 65°34'S 64°59'S 64°20'S LONG: 15°42'W 17°25'W 23°38'W 36°46'W 42°00'W 46°04'W Stat: 71/210 71/222 VII 71/223 VIII 71/244 LAT: 64°03'S 63°21'S 62°08'S 63°17'S 60°03'S 56°53'S LONG: 48°15'W 52°51'W 57°31'W 53°14'W 55°24'W 62°31'W Expected results and further processing We will determine the isotope composition of Nd and, for the first time of Hf, in both dissolved and particulate form to characterize the isotopic composition of the different Southern Ocean water masses, their sources, and mixing relationships. This will enable new insights into the influence of weathering processes of the Antarctic continental landmass on the geochemical composition of the Southern Ocean, as well as a detailed isotopic characterization of the water masses prevailing in the Atlantic sector of the Southern Ocean and the Weddell Sea. The new data will allow a more reliable application of the Nd/Hf isotope systems for reconstructions of past weathering regimes and ocean circulation. In the home laboratory, the FeOOH precipitates of the samples will be centrifuged and separated from the remaining supernatant. To remove most of the organic matrix, the samples will be treated with aqua regia after drying. The next step will be the separation of the Hf and Nd from Fe of the FeOOH-precipitate, which will either be carried out by backextraction* or large volume (40 ml resin) cation separation columns. "Hf" and "Nd" cuts will then be collected separately. The "Nd" cuts will be further purified through additional cation column steps to separate the REEs from Ba and achieve a pure rare-earth-element (REE) cut. To separate Nd from other REEs, a Ln-SPEC resin will be used. The "Hf" cut will be further purified by a one step column chemistry modified after (Münker et al., 2001). The isotopic composition will then be measured on a Nu-Instruments multi-collector-inductively coupled plasma mass spectrometer (MC-ICPMS). For the measurements of the Nd and Hf concentrations of each sample, a Nd and Hf spike will be added to each 2 L aliquot to determine the concentrations by the isotope dilution method on the MC-ICPMS. *: Trace elements, which are adsorbed on the FeOOH-precipitate, are dissolved in 6M HCI together with the precipitate. Iron forms a HFeCI4- complex which is taken up by di-ethylether (Nachtrieb and Conway, 1948; Nachtrieb and Fryxell, 1948). The residual trace elements stay in the aqueous solution and can be separated. References Godfrey, L.V., White, W.M. and Salters, V.J.M., 1996. Dissolved zirconium and hafnium distributions across a shelf break in the northeastern Atlantic Ocean. Geochimica et Cosmochimica Acta, 60(21): 3995-4006. McKelvey, B.A. and Orians, K.J., 1998. The determination of dissolved zirconium and hafnium from seawater using isotope dilution inductively coupled plasma mass spectrometry. Marine Chemistry, 60(3-4): 245-255. Münker, C., Weyer, S., Scherer, E. and Mezger, K., 2001. Separation of high field strength elements (Nb, Ta, Zr, Hf) and Lu from rock samples for MC-ICPMS measurements. GEOCHEMISTRY, GEOPHYSICS, GEOSYSTEMS, 2. Nachtrieb, N.H. and Conway, J.G., 1948. The Extraction of Ferric Chloride by Isopropyl Ether. I. J. Am. Chem. Soc., 70(11): 3547-3552. Nachtrieb, N.H. and Fryxell, RE., 1948. The Extraction of Ferric Chloride by Isopropyl Ether. II. J. Am. Chem. Soc., 70(11): 3552-3557. van de Flierdt, 1., Frank, M., Lee, D.-C. and Halliday, AN., 2002. Glacial weathering and the hafnium isotope composition of seawater. Earth and Planetary Science Letters, 201(3-4): 639-647. 3.3.6 Rare earth elements and barium Ingrid Stimac Alfred-Wegener-Institut not on board: M. Rutgers van der Loeff, Alfred-Wegener-Institut Objectives The varying REE-pattern is transferred to the ocean via processes such as riverine inputs, dust inputs, or leaching of shelf sediments and ice drifted sediments. In addition to selective weathering, elemental fractionation may also occur during aqueous transport, where natural particles and colloids are of great importance. The REE concentrations coupled with the Nd isotopic ratios (subproject 3.3.5) are powerful tracers to investigate scavenging processes and to predict the fate of elements brought from the continent. The REE's residence times on the order of 1000 years make them ideal tracers for water masses as it allows for long distance transport while preventing complete homogenisation. The geochemistry of barium is closely linked to that of radium. For the interpretation of our measurements of radium it is important to know the barium and silicate as well. Work at sea Samples were collected for REE in dissolved and particulate form. For dissolved REE 1 L of seawater was collected in surface waters and at deep stations using the NIOZ Titanium-Rosette. Such samples were obtained at all superstations along with the sampling for 231Pa and 230Th and barium. Particulate REE in surface waters has been collected by the ship's seawater pump and a continuous flow centrifuge. At each superstation, 2,500 - 5,800 L of seawater was centrifuged at a rate of about 500 - 1,000 L per hour at 16,000 g. The combined centrifugate, a brown-green paste with a high content of phytoplankton and sea-salt, was stored frozen. It will be freeze dried and analyzed for its elemental composition at AWL 3.3.7 Iron isotopic fractionation near the Antarctic Peninsula Patrick Laan, C. Thuroczy, Cornelis van Slooten, Hein de Baar NIOZ not on board: M. Staubwasser (University Köln), M. Rutgers van der Loeff, D. Abele Alfred-Wegener-Institut Objectives On the occasion of approaching the Antarctic Peninsula towards Jubany the objective is to collect seawater samples to complement the IPY project CIicOPEN (Doris Abele; Eol#1 93; full proposal #34) on the issue of iron stress on near-shore ecosystems of the Antarctic Peninsula. Briefly it is planned to assess the ratio of stable isotopes of iron (Fe) to link the high coastal Fe concentrations with semi continuous surfacewater profiles to the growth-limiting concentrations far offshore. Such a transect is especially interesting for studies of Fe isotopic composition, which can be measured at far better precision at these elevated concentrations and thus will allow to identify any isotope fractionation during early Fe uptake. Samples for Fe isotopic composition studies are to be collected (cooperation with Michael Staubwasser, University Köln). Work at sea We have done five shallow casts with the ultraclean Rosette, at overall five stations on the approach towards the Antarctic Peninsula. At three to five depth horizons samples of 20 to 50 liters were collected for iron isotope analysis. The seawater samples were all filtered, some on membrane filters, others over a filter cartridge (0.2 micron Sartorius Sartobran 300). Moreover filtrations have been done in another approach over a suite of two filter membranes of 5 micron and 045 micron nominal size cutoff respectively, placed in-line such that the first 5 micron filter takes out the larger size class marine particles, and next the finer 045 micron filter removes the smaller size class particles. The membrane filters were stored in the freezer for isotope analyses as well. In parallel for selected stations and selected depths the distribution of dissolved trace metals Fe, Mn and Al was sampled, and analyzed in context of projects 3.1.1. and 3.1.3, respectively. For exact information on sampling, filtrations and ancilliary samples for Fe, Mn Al, see the Excel sheet of each station hydrocast Gi to G5. 3.3.8 δ 13C of particulate organic material in the Southern Ocean Elisabeth Sweet Alfred-Wegener-Institut not on board: D. Wolf-Glad row, U. Passow, C. De La Rocha, Alfred-Wegener-Institut Objectives The Southern Ocean may have been essential for the drawdown of atmospheric CO2 during glacial periods. In order to reconstruct the state of the Southern Ocean during glacial periods and the processes responsible for altered states various paleo-proxies including δ13C(org), δ15N, δ°30Si, have been proposed and applied. A major problem for the application of δ13C(org), as a paleo-proxy is its large variation in the Southern Ocean and the unknown origin of isotopically very light organic material (δ13C(org) below -30%). Our goal is to identify the phytoplankton species responsible for this light material, to look for variations under various growth conditions, and to investigate the relationships between δ13C(org) to other paleo-proxies based on consistent data sets. The work will contribute to the international programme GEOTRACES (2006). Work at sea Samples containing in-situ phytoplankton were collected from the chlorophyll maximum at 5 stations and 6 super stations on the Greenwich meridian transect. The depth of the mixed layer was determined based on the CTD profile and where no clear chlorophyll maximum peak was present, a depth of 50 m was used as a standard depth. In order to separate different plankton groups the suspended particulate material was fractionated sequentially into 5 size classes: 0.2 - 1.2 µm, 1.2 - 5 µm, 5 - 20 µm, 20 100 µm and > 100 µm. The particulate material collected from each size fraction was resuspended immediately after sampling in 0.2 µm filtered sea water from the previous station, by rigorous shaking in a glass bottle in a similar procedure as that suggested by Rau et al. (1999). To evaluate the collected species composition and further characterize the particulate material sampled 20 ml of the suspension were transferred into a 25 ml screw capped scintival and chemically fixed for later microscopic investigation. The remaining suspension was filtered through a precombusted glass fibre filter (GF/F 25 mm diameter) for the four larger size fractions and through a precombusted silver filter (25 mm diameter) for the 0.2 pm size fraction. These filters were frozen for isotopic analysis, which will be conducted at the Alfred Wegener Institute. The large diatoms (Corethron sp., Fragilariopsis kerguelensis) common in the Southern Ocean will be collected in the > 100 µm fraction, whereas the smaller diatoms like Pseudonitzschia sp. and many protozoa will be collected in the 20 - 100 µm fraction. Copepods caught in the large size fractions will be hand picked off the filters. Flagellates of Phaeocystis antarctica and other flagellates will dominate the 5 - 20 µm fraction. Bacterio-plankton (0.2 -1.2 µm) and picoplankton (1.2 - 5 µm) will dominate the two respective smallest fractions. A minimum of 50 - 80 µg of carbon per filter is required for the measurement of δ13C(org). At a chlorophyll concentration of 0.5-2 µg L(^-1) and a carbon: chlorophyll ratio of 40 g g(^-1) filtration of 20 to 40 L of seawater will collect enough material for δ13C(org) measurements of samples fractionated into 5 size classes. This has been confirmed by measurements performed within an earlier fractionation experiment. The amount of water filtered was determined at each station according to the chlorophyll concentration, which is measured online as fluorescence and the amount of particulate material present in the sample during filtration. Smaller volumes of water were required for filtration through the smaller size fractions. Preliminary results Isotopically extremely light values (δ13C(org) < -28 ‰) were consistently observed at stations south of the Polar Front, with values δ13C(org) < -30 ‰ in at least one size fraction at 4 stations. The fractionations εp indicate that the produced organic carbon was appreciably lighter (+ 14 to 20 ‰) than the source DIC implying that biology is a key factor responsible for the isotope ratios. 3.3.9 Mapping the distribution of Si isotopes in Southern Ocean waters Elisabeth Sweet Alfred-Wegener-Institut not on board C. L. De La Rocha, Alfred-Wegener-Institut Objectives The Silicon isotopic composition of sedimentary diatoms is a key proxy for reconstructing nutrient cycling in the Southern Ocean and its impact on atmospheric CO2 over past climate cycles. It is considered to reflect the extent to which the nutrient, silicic acid, is removed from the euphotic zone in support of primary production. The extent of CO2 uptake during primary production relative to the upwelling of CO2-rich deep waters in the Southern Ocean, in turn, has a strong influence on atmospheric concentrations of CO2. To date paleoceanographic reconstructions of silicic acid draw down in the Southern Ocean, south of the present day Antarctic Polar Front (APF), has produced conflicting results with that of nitrate draw down. The Si isotopic composition of diatoms has suggested that silicic acid is more completely consumed during interglacials, and is utilized to a significantly lesser extent during glacials, especially the last glacial maximum (LGM) and the maximum of the penultimate glacial cycle. The nitrogen isotopic composition of organic matter trapped within the siliceous framework of diatoms, however, suggests the opposite pattern for nitrate utilization. The objective of this work is to map both the distribution of Si isotopes in dissolved nutrients in surface waters in the Southern Ocean, providing information as to the range and variability of the variations (especially of the isotopic composition of nutrients) over a fine spatial scale and to examine the Si and composition of seawater and diatoms in the Southern Ocean. Work at sea Samples were collected at 4 stations on the Greenwich meridian transect and 2 on the Weddell Sea transect. 16 depths per cast were sampled to construct a complete depth profile on these stations from depths ranging from 10 meters at the shallowest down to 5000 meters at the deepest (although most sites were shallower than this). At Station PS71/115-2 a reduced 7 depth profile was sampled to enable an intercalibration with the Marion Dufresne: Once the samples were collected the water was filtered throught 0.6 pm polycarbonate filters to obtain biogenic (BSi) and lithogenic (LSi) silica concentrations; and δ30Si of dissolved silicon. The parameters sampled for will be measured back at the AWL Preliminary results 70 depths were sampled from 6 different CTD casts on the first part of the cruise ANT-XXIV/3. These samples fall along a cruise track that covered temperate to polar regimes, crossed over the Antarctic Divergence, the Antarctic Polar Front, and the Subantarctic Front, regions of low Fe availability as well as those (down wind of land masses or on the Kerguelen Plateau) where Fe may be abundant, and both open and coastal waters. The samples taken should allow for documentation of shifts in isotope values over a broad range of conditions. This will help us to improve Si isotope-based paleoceanographic reconstructions of nutrient utilization and CO2 removal. The data sets produced, in addition to enhancing our understanding of a proxy fundamental to reconstructions of Southern Ocean paleoceanography, falls under the auspices of the IPY umbrella project, BIPOMAC, and will also contribute to the trace metal and isotope mapping efforts of GEOTRACES. 3.3.10 Uranium isotopes Ingrid Stimac(1), Hein de Baar(2) (1)AIfred-Wegener-Institut not on board: B. Moran(3), (2)NIOZ M. Rutgers van der Loeff(1) (3)University of Rhode Island Objectives New methods are now available for more accurate determination of the isotopic composition of uranium (U) in seawater. This allows better insight in the geochemistry of U in the oceans. One important aspect is to be able to distinguish the U isotopic signal of different water masses. Work at sea In an effort to capture the core water masses of Antartic Intermediate Water (AAIW), the underlying water of North Atlantic Deep Water origin, and the Antarctic Bottom Water, 10 samples of 4 L each have been collected at a station situated north of the Polar Front, as to be able to sample AAIW which forms at the Polar Front, and does not exist South of the Polar Front. The station positioned at 44°39.69'S, 7°5.59'E (PS71- 102-2 at 15.02.2008) was sampled at depths of 300, 400, 500, 750, 1,000, 1,500, 2,000, 2,500, 4,000 and 4,500 m. Each sample was acidified with 1 ml/liter of Seastar 12M HCI baseline grade (this acid was available in context of project 3.15. on Cd isotopes) and then stored for future analysis by Brad Moran. 3.4 Nutrient measurements during ANT-XXIV/3 Jan van Ooijen NIOZ Background On this cruise samples were analysed on phosphate, silicate, nitrate and nitrite. At the end of the cruise there will be about 18,000 analysis (4,500 samples) accomplished on a Bran and Luebbe Traacs800 Autoanalyser connected to an autosampler. The different nutrients were determined colorimetrical as described by Grashoff (1983). Methods Samples were obtained from a CTD rosette sampler, an ultraclean CTD and of algae growth experiments. All samples were obtained in a polyethylene vial and the samples of the algae growth experiment were filtered over a 020 pm acrodisc filter. They were all stored dark at 4°C. CTD samples were analysed within 12 hours all other samples within 24 hours on a Technicon TrAAcs 800 autoanalyzer. Standards were prepared fresh every day by diluting the stock solutions of the different nutrients in nutrient depleted surface ocean water. This water is also used as baseline water. Each run of the system ha,d a correlation coefficient for 9 calibrant points of at least 0.9999. The samples were measured from the lowest to the highest concentration in order to keep the carry over effects as small as possible. In every run a mixed nutrient standard containing silicate, phosphate and nitrate in a constant and well known concentration, a so called antarctic nutrient-cocktail, was measured in duplicate. This cocktail is used as a guide to check the performance of the analysis and used to make a correction at the end of a transect obtaining the final data. Over the last 20 years this cocktail has proven to be stable for at least 10 years and has also been used and monitored in many intercomparisment tests (ICES, Quasimeme). The reduction efficiency of the cadmium column on the NO manifold was as least 97 % and measured in each run. Chemistry Silicate reacts with ammoniummolybdate to a yellow complex, after reduction with ascorbic acid the obtained blue silica-molybdenum complex was measured at 800 nm. Oxalic acid was used to prevent formation of the blue phosphatemolybdenum. Phosphate reacts with ammoniummolybdate at pH 1.0, and potassiumantimonyltartrate was used as an inhibitor. The yellow phosphate-molybdenum complex was reduced by ascorbic acid and measured at 880 nm. Nitrate plus nitrite (NOx) was mixed with a buffer imidazol at pH 7.5 and reduced by a copperized cadmium column to nitrite. This was diazotated with sulphanylamide and naphtylethylenediamine to a pink colored complex and measured at 550 nm. After subtracting the nitrite value of the nitrite channel the nitrate value was achieved. Nitrite was diazotated with sulphanylamide and naphtylethylenediamine to a pink colored complex and measured at 550 nm. Statistics after corrections for the Greenwich meridian transect The standard deviation of reference material within a run: P04: 0.006 uM 0.16% of full scale value Si: 0.084 uM 0.06% of full scale value NOx: 0.063 uM 0.13% of full scale value NO2: 0.001 uM 0.05% of full scale value The standard deviation of reference material between the runs are: P04: 0.009 uM 0.27% of full scale value Si: 0.464 uM 0.33% of full scale value N0: 0.222 uM 0.24% of full scale value NO2: 0.006 uM 0.39% of full scale value Suspicious bottles Bottles which seem not to have closed at the right depth at the Greenwich meredian transect are: CTD 106-1-1 CTD 127-1-2 CTD 134-1-4 or CTD 134-1-1 Preliminary results An overlook of the results of the nutrient analysis on the Greenwich meridian transect is plotted in ODV (Fig. 333). Fig. 3.33: Vertical transects of SI and NO along the Greenwich meridian 3.5 Silicate measurements with cyclic voltammetry Marielle Lacombe and Veronique Garcon CNRS/LEGOS Background and General Objectives Real time, long-term in-situ monitoring of the ocean, leading to the acquisition of repeated measurements without having a ship at sea permanently, constitutes a crucial step to increase our knowledge of the ocean. Chemicals in the ocean play an essential role and particularly nutrients controlling photosynthesis. Electrochemistry seems a well adapted method for in-situ measuring of bioactive components in extreme conditions found in the ocean. The potentialities of the voltammetric methods for the analysis of various chemical species in the marine environment have already been demonstrated. They allow to measure several species simultaneously and this down to very low concentrations and without reagent (Luther et al., 2007). Moreover, microelectrode techniques are particularly adapted to high pressure environments. In this context, we developed a new method for silicate determination in the ocean using no reagent (Lacombe et al., 2008). Silicates are non-electroactive species. The method involves complexing molybdenum salt in acidic medium with silicate to make it electroactive. This method was compared during Drake ANT-XXIIII3 Cruise (Polarstern, PI C. Provost) with the classical colorimetric one in Drake Passage, and showed excellent results (Lacombe et al., 2007). The variability of the different water masses of this key passage was also studied using hydrographic parameters. The Drake Passage is an important entry point for several water masses from the Pacific into the Atlantic Ocean. They are carried by the Antarctic Circumpolar Current (ACC) around the Antarctic continent and thus can enter in the South Atlantic and the Weddell Sea. Our objective is to compare the present picture of water mass mixing with that of the Drake Cruise in 2006 (ANT-XXIIII3), and in particular the SPDW (South Pacific Deep Waters) spreading. We will also document water mass mixing along the Greenwich meridian. Work at sea We sampled for silicate determination along Greenwich meridian-Drake transects (along the Greenwich meridian and in the Weddell Sea). The samples were analyzed on board by cyclic voltammetry with a glassy carbon electrode, with an Ag/AgCI reference electrode and a carbon counter electrode. The detection method was developed on new working electrodes to avoid the manual polishing that is required with the glassy carbon one for a complete autonomous measurement. Electrochemical measurements were carried out with a Metrohm potentiostat and with a newly developed autonomous submersible potentiostat. Preliminary results The new electrochemical detection method was developed and tested on board on gold and platinum electrodes during the Greenwich meridian transect, and the Weddell Sea section allowed us to test the stability of the response. The oxide formed at the electrode surface appears not to be very stable and more experiments are needed to yield a fully satisfying method. The autonomous submersible potentiostat had electronic problems and was out of use. One of the mains problem encountered was the leaking of the measurement cell. This problem will be easily solved back in the laboratory. The profiles obtained will be compared with the classical silicate determination carried out by colorimetry by the NIOZ team along the Weddell Sea transect. The study of the stability of the measurements will allow us to conclude on the potentialities to adapt this new method on a autonomous in-situ sensor. The distribution of silicate concentrations will document the different water masses along the Greenwich meridian and in the Weddell Sea. References Lacombe M., Garcon V., Comtat M., Oriol L., Sudre J., Thouron D., LeBris N., Provost C., 2007. Silicate determination in sea water: toward a reagentless electrochemical method. Marine Chemistry. 106, 489-497. Lacombe M., Garcon V., Thouron D., Le Bris N., Comtat M., 2008. A new electrochemical reagentless method for silicate measurement in seawater. Talanta. submitted. Luther G.W., Glazer B.T., Ma S., Trouwborst RE., Moore IS., Metzger E., Kraiya C., Waite T.J., Druschel G., Sundby B., Taillefert M., Nuzzio D.B., Shank TM., Lewis B.L., Brendel P.J., 2008. Use of voltammetric solid-state (micro) electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in-situ electrochemical analyzer (ISEA). Marine Chemistry. In Press, -. 3.6 Intercomparison of GEOTRACES variables with BONUS-GOODHOPE Hein de Baar(2), Patrick Laan(2), (1)Alfred-Wegener-Institut Elisabeth Sweet(1), Celia Venchiarutti(1), (2)NIOZ Ingrid Stimac(1), not on board: M. Rutgers van der Loeff(1), (3)LEMAR, CNRS-UMR C. de la Rocha(1) (4)Vrije Universiteit Brussel On board Marion Dufresne: Marie Boye(3), (5)Royal Museum for Central Africa Frank Dehairs4, Matth ieu Roy-Barman(6) (6)CNRS Damien Cardinal(5), not on board: C. Jeandel For the sections from Cape Town to the Greenwich meridian, and from there along Greenwich meridian to Antarctica, the CASO-GEOTRACES programme of Polarstern ANT-XXIV/3 was complementary to the BONUS- GOODHOPE programme aboard Marion Dufresne. Towards an overall integrated database of both expeditions, some intercomparison between both programmes had been envisioned. Before departure from Cape Town, where Marion Dufresne was also in port, there had been a meeting on board Polarstern for organizing the intercom parison. This had to be modest for following reasons: - departure of both vessels from Cape Town was delayed with many days for various reasons, at expense of scientific stations time, - adverse weather conditions in the Southern Ocean caused more time losses, - the extensive research objectives of both expeditions were very ambitious, - the number of pre-cleaned sample bottles on board both ships was limited. The agreed strategy was twofold. Firstly the initial cruise tracks of Polarstern and Marione Dufresne had been scheduled to be overlapping, and that, in principle, allowed the positioning of stations and sampling depths at the same place. That was the strategy of choice for intercomparison of CO2 system measurements, see further section 43, and for major nutrients. Secondly for a limited number of variables, it had been decided that both ships would take a small number of duplicate samples to be exchanged after the expeditions were completed, for final analyses at the home laboratories. These variables are barium, dissolved trace metals, neodymium I thorium-Isotopes I protactinium (NdfTh/Pa), and silicon isotopes. Once at sea, Polarstern, due to its earlier departure, was further south than Marion Dufresne. On 26 February the positions and sampling depths of Polarstern stations completed up to then (then until 59°S, 0°W) were communicated to Marion Dufresne to allow their re-occupation of selected mutual stations, their overall research programme, weather permitting. Moreover 12 duplicate samples (Ingrid Stimac) for barium at 46°S, 5°53'E (PS71103-1 at 16.02.2008) were collected on Polarstern, 10 duplicate filtered seawater samples (Patrick Laan) for trace metals at 47°40 5 4O.7l E (PS71-104-2 at 16.02.2008); 3 duplicate samples (Celia Venchiarufti) for Nd/Th/Pa at 52°59.58S 0°2.39E (PS71/113-4 at 20.02.08); and 7 duplicates (Elizabeth Sweet) for Si isotopes at 53°31'S, 0°0.30'E (PS71-115-2 at 21.02.2008). Similarly the BONUS-GOODHOPE team aboard Marion Dufresne collected several replicate samples (Marie Boye) for trace metals at 10 depths at 43°33.16' S, 4°22.36'E (their station GF-19 cast S3 on 04.03.2008), and 3 replicate samples (Matthieu Roy-Barman) for Nd/Th/Pa at 52°59'S, 0°E. Damien Cardinal agreed to take replicates for Si isotopes at same location as above for such replicates taken on Polarstern, actual sampling yet to be confirmed. 4. DISSOLVED CARBON DIOXIDE IN THE SOUTHERN OCEAN 4.1 Deep-ocean carbondioxide chemistry (DIC, TAlk) Steven van Heuven(1),(2), Hans Slagter(1),(2) (1)NIOZ not on board: H. Zemmelink(1), (2)University of Groningen M. Hoppema(3) (3)AWI Objectives In the last 250 years large amounts of CO2 have been emitted to the atmosphere as a result of human activity. A significant fraction (50%) of this 'anthropogenic CO2 has subsequently been taken up by the oceans, which by doing so, are having a dampening effect on the speed of the climate change predicted to result from the increasing atmospheric CO2 concentration. The total amount of anthropogenic CO2 taken up, current and past rates of uptake, the potential decline in uptake due to saturation of the surface ocean and the deleterious effect on marine life resulting from the acidification associated with the increasing amount of dissolved inorganic carbon (DIC) of the oceans are current focusing points of the fields of marine chemistry, biogeochemistry and biology. Next to laboratory and field studies aimed at conceptual and mechanistic understanding of the many processes involved, a large effort is being made to investigate the state of the carbonate system in the world's oceans. This is performed almost exclusively through research cruises since no remote sensing or automated profiling systems are currently available for this task. In order to be able to calculate the exact state of the carbonate system (i.e., the precise concentrations of all substances constituting DIC), one additional of the four measurable parameters of the carbonate system (pH, pCO2, DIC, total alkalinity) must be determined. The setup that was used here measures TAlk and DIC of each sample simultaneously. Work at sea High-precision measurements were made of the dissolved inorganic carbon (DIC) content and total alkalinity (TAlk) of samples collected at 126 oceanographic stations. This yielded at total of 2,400 unique samples of which a subset (400) was analyzed on both machines to allow for intercalibration. Analysis of DIC was performed using the coulometric method (Johnson et al., 1993; DOE, 1994). TAlk analysis was carried out with acid titration (Gran, 1952; Bradshaw et al., 1981; DOE, 1994). Both analyses were performed using a single integrated system: the VINDTA (Versatile Instrument for Determination of Titration Alkalinity; MARIANDA: Marine Analytics and Data, Kiel, Germany). Drift control and accuracy of the analyses were maintained through extensive use of labstandards and certified reference material (CRM, supplied by Dr. A. Dickson, Scripps Institution of Oceanography). Technical details on methods used Two VINDTA setups were used concurrently, often running a sample 'together' drawing from the same sample bottle at the same moment. These 'duplicates' are used to ensure system intercomparability. As to the determination of DIC by coulometry: a precisely known amount of sample (20 ml) is dispensed from an automated, thermostated pipette into a stripper. The sample is acidified here, converting the two carbonate species into dissolved CO2(aq). The evolving CO2 is rapidly removed from the sample by sparging with N2. The CO2-enriched N2 stream is led through the solution in the coulometric cell, which absorbs the CO2 and becomes more transparent. The coulometer subsequently electrically titrates the solution back to its original opacity. The required amount of charge is a linear measure of the amount of CO2 absorbed. Total alkalinity is mathematically derived from a titration curve, fitted in an electrochemically consistent manner along data of electrode potential derived from an acid-titration of an accurately known amount of sample (100 ml), dispensed with an automated, thermostated pipette. Titration is performed in a thermostated cell. With knowlegde of the sample's volume and density, the concentrations of the DIC and total alkalinity in the sample are easily calculated. Samples, collected without headspace in 600 ml Duran bottles, where brought to analysis temperature (25°C) by flowing through a heat exchanger on their way from the sample bottle to the VINDTAs. Samples were injected into the system under a slight overpressure (0.4 bar), which fully suppressed the bubble formation often associated with the drawing of sample into the VINDTA using a peristaltic pump. Lab standard was prepared on board in batches of 60 L by filtering and poisoning water collected with the CTD from around 2,000 m deep, or simply from the ship's surface water tap. For the later batches, the pCO2 of the batch was, prior to use, brought to 1.4 times the atmospheric value (thus 550 patm) by sparging, so that upon headspace pressurization no significant CO2 exchange with the lab standard headspace would occur. The sparging process was monitored with a LiCor 7000 infrared gas analyzer. Approximately every 5th analysis was followed by analysis of this labstandard, and CRM was analyzed 3 or 4 times per day in order to set accuracy and to detect and be able to correct for measurement drift. Every CRM-sample was run on both machines at the same time. A definitive way of application of corrections is still to be decided upon. Measurements were performed in a thermostated container, with the components most sensitive to sudden temperature drops (caused by the turning on of the air conditioning unit), being thermally insulated in order to smooth out those peaks. Examples of the obtained data are displayed in figures 4.1 and 4.2. References Bradshaw, A.L., Brewer, P.G., Shafer, D.K., Williams, R.T., 1981. Measurements of total carbon dioxide and alkalinity by potentiometric titration in the GEOSECS programme. Earth and Planetary Science Letters 55, 99-115. DOE, 1994. Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. Version 2, A. G. Dickson & C. Goyet, eds. ORNL/CDIAC-74 Gran, G., 1952. Determination of the equivalence point in potentiometric titrations. Analyst, 77, 661-671. Johnson, KM., Wills, K.D., Butler, D.B., Johnson, W.K., Wong, CS., 1993. Coulometric total carbon dioxide analysis for marine studies: maximizing the performance of an automated gas extraction system and coulometric detector. Marine Chemistry, 44, 167-187. Fig. 4.1: Preliminary results for the section along the Greenwich meridian for DIC. These data are quite close to being final. Fig. 4.2: Preliminary results for the section along the Greenwich meridian for TAlk. Please note that additional correction of these data has yet to be performed. 4.2 Surface water carbondioxide chemistry (DIC, pCO2) Steven van Heuven(1),(2), Hans Slagter(1),(2) (1)NIOZ not on board: H. Zemmelink(1), (2)University of Groningen C. Nei11(3) (3)University of Bergen Objectives The increase in the atmospheric CO2 content is not equal to the cumulative emissions from human activities because about half of these emissions are taken up by the world's oceans. This leads to the increase in DIC which is the subject of the research described in the previous paragraph (deep-ocean carbonate chemistry). However, these oceanic inventory changes are not the only measure of the processes involved in the distribution of this anthropogenic CO2 between the ocean and atmosphere. Since exchange of CO2 between these two compartments necessarily takes place across the sea surface, global quantification and (temporal and spatial) integration of these fluxes should yield an independent measure of DIC accumulation in the world's oceans. Quantification of these fluxes requires accurate knowledge of the partial pressure of CO2 (pCO2) of both the atmosphere and surface ocean. Determination of the atmospheric concentrations is now common practice around the world, but the determination of the highly variable sea surface pCO2 has historically proven to be much more complicated. However, several research groups around the world are involved in major efforts to fill in this gap, using highly specialized (though now standardized) equipment. Already these investigations have resulted in global, seasonal pCO2 maps, from which, with information of wind speed and atmospheric pCO2 fields, fluxes can be calculated with reasonable accuracy. The monitoring of the sea-surface carbonate system will contribute to this effort. Work at sea A fully autonomous, continuous surface water pCO2 system has been permanently installed on Polarstern since 2007. This system draws water from the ship's seawater supply. A steady flow of this water is led through a plastic 'equilibrator' vessel, filling it almost halfway before flowing out into the ship's drain. The air in the headspace of this equilibrator is circulated through a LiCor 7000 infrared gas analyzer. Because the air after a short while takes on the pCO2 value of the water, the pCO2 of the analyzed air is identical to that of the water. By using several sensors and methods, all measurements are corrected for vapour pressure and temperature effects, which may cause significant deviations of the equilibrated pCO2. Four calibration gases (0, 175, 350 and 700 patm) are available for hourly recalibration of the gas analyzer. Atmospheric air is measured every hour. pCO2 values as well as diagnostic and auxiliary data (mainly GPS and meteorological observations), are logged and automatically sent to the home laboratory through email. Operation of the pCO2 system consisted of little more that turning it on and keeping an eye on reference gas availability and the different diagnostic indicators. In order to fully determine the state of the carbonate system in the surface ocean, a second of the four measurable parameters of the carbonate systems (DIC, TAlk, pCO2 and pH) has to be determined. From the work done by Craig Neill during the previous cruise leg ANT-XXIV/2, a continuous surface water DIC analyzer was available, which we have used to continue his work. This system is built up around the heart of the SOMMA system, but now equipped with an automatic intake and the capacity to measure continuously, unattended, until the coulometer chemicals need to be replenished. This setup allowed for the determination of 3 - 4 samples every hour, for a cruise-leg total of 4500, which should allow us to determine the exact state of the carbonate system to an exacting degree. The ~20 ml sampling pipette was thermostated to the temperature of the sample, using a second line from the sea water tap. This means that the pipette volume changes with the sample temperature, as does - of course - the sample's density. Corrections for all these effects will be applied after the cruise. For the calibration of the SOMMA system (and as a means of checking the pCO2 system as well), the VINDTA-analyses (see 'deep-ocean carbonate chemistry') of the uppermost samples of the regular hydrocasts (from circa 10 meters depth) were used. Whenever no hydrocasts were being performed for a significant amount of time, samples tapped from the ship's seawater supply (from which the SOMMA get its water as well) were analyzed. The assumption that the water from 10 m depth resembles the water from 5 m depth (at the ships sea water supply inlet) will be tested for validity. 4.3 Intercomparison of carbondioxide variables with BONUS-GOODHOPE Steven van Heuven(1), Hans Slagter(1), (1)NIOZ Hein de Baar(1) (2)Université de Liege On board Marion Dufresne: (3)Universidad de Las Palmas de Bruno Delille(2), Gran Canaria Nicolas-Xavier Geilfus(2), Meichior Gonzalez-Davila(3), J. Magdalena Santano-Casiano(3) For the sections from Cape Town to the Greenwich meridian, and from there along zero meridian to Antarctica, the CASO-GEOTRACES programme of Polarstern ANT-XXIV-3 was complementary to the BONUS-GOODHOPE programme aboard Marion Dufresne. Towards an overall integrated database of both expeditions, some intercomparison between both programmes had been envisioned. The initial cruise tracks of Polarstern and Marione Dufresne had been scheduled to be overlapping, and that in principle allowed the positioning of stations and sampling depths at the same place. This was the strategy of choice for intercomparison of CO2 system measurements, which had already been calibrated routinely on both ships by the shipboard use of certified reference material (CRM, supplied by Dr. A. Dickson, Scripps Institute of Oceanography). Once at sea, Polarstern, due its earlier departure, was further south than Marion Dufresne. On 26 February 2008 the positions and sampling depth horizons (pressure, salinity, temperature at 22 - 24 depths per station) of 21 stations with CO2 system data aboard Polarstern (then until 59°S, 00) which had been completed up to then were communicated to Marion Dufresne. These were twenty-one (21) ANT-XXIV/3 stations PS71-101 until PS71-131 from positions 42.3379°S, 8.9946°E (101) to 59.00°S, 0.00° (131). This allowed re-occupation of selected same stations by BONUS-GOODHOPE, its overall research programme, weather permitting. Indeed BONUS-GOODHOPE was able to occupy sixteen (16) stations BGH-44 to BGH-78 from 46.0242 5, 5.865 E (BGH-44) to 57.5°S, 0.0365°E (BGH-78) with their respective CTD hydrocast numbers CTD-57 to CTD-106. Among these BONUS-GOODHOPE stations were ten (10) stations within 5 nautical miles of most nearby ANT-XXIV/3 stations of Polarstern. The listing of exact stations positions is available in an excel sheet. 5. MARINE BIOLOGY In addition to the marine biological projects 5.1. and 5.2. described below, one is referred to two other projects with strong biological focus: 3.1.7. The effect of dynamic light conditions and iron limitation on phytoplankton abundance 3.1.8. The Southern Ocean in a high-CO2 World 5.1 The significance of viruses for polar marine ecosystem functioning Claire Evans, E. Frijling, NIOZ not on board: C. Brussaard, NIOZ Background and Objectives Microbial communities (phytoplankton, bacteria, Achaea, heterotrophic protozoa and viruses) comprise the majority of the biomass in the oceans and drive nutrient and energy cycling, and are thereby important components of polar food webs. With the emergent awareness that viruses are major players influencing biodiversity and biogeochemical processes the need to elucidate their role in polar ecosystems has been underlined as, despite their likely importance, their quantitative significance has barely been studied. We aimed to complete a comprehensive study of the viruses and viral mediated processes of the Antarctic marine habitats encountered during ANT-XXIV/3. The objectives of this study were; 1) To examine the abundance and composition of viruses and their prokaryotes and eukaryotic hosts, 2) To determine viral induced mortality on both prokaryotic and eukaryotic microbial hosts alongside host growth rates and mortality due to grazing. 3) To gather a data set allowing comparison of the viruses and viral mediated processes of the Southern and Northern Polar regions. 4) To collect sample from which viruses might be isolated and therefore available for laboratory experiments. Work at sea Daily profiles were made of algal abundances (cyanobacteria, picoeukaryotes and nanoeukaryotes) by flow cytometry of fresh samples. Additionally samples for viral and bacterial abundance were fixed with glutaraldehyde, snap frozen and stored at -80°C for later analysis at NIOZ by flow cytomtery and SYBR Green. On experimental stations measurements of abundance, growth rate, diversity, grazing rate and viral-induced mortality were performed on the bacterial community at surface, chlorophyll maximum and 200 m or both the algal and bacterial community at the chlorophyll maximum. Details of the stations sampled are given in table one. At all experimental stations, samples were taken for viral diversity by concentrating 10 L volumes by 30 kDa ultrafiltration. These samples will be stored at -80°C until analysis by pulse field gel electrophoresis at the NIOZ. Samples for algal and bacterial diversity were collected by filtration of approximately 1 L volumes of whole seawater onto 1 and 0.2 µm polycarbonate filters respectively which were snap frozen and stored at -80°C and will be analyzed at the NIOZ by denaturing gradient gel electrophoresis. Growth rates, viral lysis and grazing of the cyanobacteria, picoeukaryote, and nanoeukaryote communities present were determined by a dilution technique whereby whole water is combined with either 30 kDa filtered water (virus and grazerfree) or 0.4 um filtered water (grazer- free) in triplicate over a dilution series and incubated at in-situ temperature and light conditions (deck incubator). Samples for algal enumeration were taken from all incubations at the start of the assay and after 24 h, allowing the calculation of growth rate. By plotting observed growth rate against the level of dilution the theoretical growth rate in the absence of mortality was calculated along with coefficients of grazing and viral induced mortality. Rates of viral induced mortality of bacteria were determined by viral reduction assay. Briefly, the bacterial community was concentrated by tangential flow filtration and resuspended in viral free water generated by 30 kDa ultrafiltration. The production of viruses was followed by sampling for bacterial and viral abundance over a 12 h period (subsampling every 3 h). Rates of lysogenic infection of the bacteria were determined in identical experiments with the addition of Mitomycin C, inducing lytic production of any lysogenic phage. In addition, rates of viral infection of bacteria will be elucidated by determining the frequency of infected cells which will be performed at the NIOZ on samples preserved with glutaradehyde. Grazing of bacteria was assessed by an exclusion assay whereby bacterial numbers within incubations filtered to remove grazers 0.8 um were compared with whole water incubations containing grazers. Secondary production was determined using the radiolabelling Leucine incorporation technique. Live and dead (fixed) subsamples of whole water were incubated for 4 hours in the dark at in-situ temperature the presence of 20 pCi. After the incubation period the samples will be killed with the addition of formalin and stored until later analysis by liquid scintillation at the NIOZ. Samples for virus isolation were collected from the chlorophyll maximum and will be screened against potential hosts at the NIOZ. Tab. 5.1: Stations sampled Station Type Station Date Time Lat Long Depth Gear [m] --------------- ----------- -------- ----- ---------- ---------- ------ ------------------------- Abundance PS71/101-2 13.02.08 16:02 42°20.22'S 8°59.88'E 4543.0 CTD, Ultra Clean Algal Bacterial PS71/101-5 14.02.08 02:49 42°20.54'S 8°59.54'E 4560.0 CTD/rosette water sampler Abundance PS71/102-2 15.02.08 07:55 44°39.62'S 7°5.82'E 4619.0 CTD/rosette water sampler Bacterial PS71/102-4 15.02.08 10:33 44°39.51'S 7°5.62'E 4618.0 CTD/rosette water sampler Abundance PS71/104-2 16.02.08 22:44 47°39.58'S 4°16.95'E CTD, Ultra Clean Algal Bacterial PS71/104-8 17.02.08 14:13 47°38.45'S 4°16.43'E 4549.2 CTD/rosette water sampler Bacterial P571/106-1 18.02.08 03:48 48°54.68'S 2°48.11'E 4101.4 CTD/rosette water sampler Abundance PS71/107-3 18.02.08 19:57 50°16.13'S 1°26.71'E 3855.0 CTD, Ultra Clean Abundance PS71/108-2 19.02.08 10:41 51°29.91'S 0°0.21'E 2771.7 CTD/rosette water sampler Abundance PS71/113-2 20.02.08 11:02 52°59.90'S 0°0.89'E 2530.3 CTD, Ultra Clean Algal Bacterial PS71/113-4 20.02.08 13:27 52°59.58'S 0°2.39'E 2544.2 CTD/rosette water sampler Abundance P571/116-1 21.02.08 06:44 54°0.07'S 0°0.01'W 2529.5 CTD, Ultra Clean Bacterial PS71/121-2 22.02.08 05:02 55°30.01'S 0°0.03'E 3750.3 CTD/rosette water sampler Abundance P571/122-1 22.02.08 14:05 56°0.03'S 0°0.23'E 3682.3 CTD, Ultra Clean Algal Bacterial P571/125-1 23.02.08 06:06 57°0.11 5 0°0.17'W 3837.3 CTD/rosette water sampler Abundance P571/127-1 23.02.08 12:05 57°30.02'S 0°0.30'E 3936.8 CTD/rosette water sampler Abundance PS71/131-4 24.02.08 17:49 59°0.04'S 0°0.07'W 4600.7 CTD/rosette water sampler Algal Bacterial PS7I/131-10 25.02.08 09:05 58°59.99'S 0°0.22'E 4608.6 CTD/rosette water sampler Abundance P571/137-1 26.02.08 08:06 60°30.00'S 0°0.08'W 5355.5 CTD/rosette water sampler Abundance PS71/141-1 27.02.08 05:34 62°0.01'S 0°0.02'W 5359.5 CTD, Ultra Clean Bacterial PS71/141-2 27.02.08 09:00 61°59.96'S 0°0.05'E 5359.5 CTD/rosette water sampler Abundance PS71/147-3 28.02.08 18:03 63°57.99'S 0°0.81'W 5193.2 CTD, Ultra Clean Algal Bacterial P571/150-1 29.02.08 08:11 64°59.94'S 0°0.27'E 3721.8 CTD/rosette water sampler Abundance PS71/150-2 29.02.08 08:34 64°59.93'S 0°0.12'E 3723.0 CTD, Ultra Clean Abundance P571/157-S 07.03.08 22:04 66°28.57'S 0°1.95'W 4495.0 CTD/rosette water sampler Abundance PS71/159-4 08.03.08 12:59 66°1.88'S 0°8.68'E 3460.5 CTD/rosette water sampler Abundance P571/163-1 09.03.08 14:04 66°59.94'S 0°0.18'W 4701.5 CTD, Ultra Clean Algal Bacterial PS71/167-2 10.03.08 07:09 68°0.04'S 0°0.00'W 4506.7 CTD/rosette water sampler Abundance P571/171-1 10.03.08 16:13 68°44.96'S 0°0.06'W 3629.5 CTD/rosettewater sampler Abundance PS71/175-3 11.03.08 08:34 68°59.77'S 0°0.23'E 3418.2 CTD, Ultra Clean Abundance P571/178-1 11.03.08 18:34 69°23.98'S 0°0.05'W 2011.7 CTD/rosette water sampler Abundance P571/184-1 13.03.08 10:54 69°0.09'S 6°59.81'W 2954.5 CTD/rosette water sampler Abundance P571/186-1 15.03.08 10:00 69°5.27'S 17°17.22'W 4763.5 CTD/rosette water sampler Algal Bacterial PS71/186-3 15.03.08 15:03 69°3.76'S 17°26.03'W 4766.2 CTD/rosette water sampler Abundance P571/187-1 15.03.08 20:38 68°48.20'S 17°57.61'W 4791.5 CTD, Ultra Clean Bacterial PS71/191-2 17.03.08 10:05 67°21.18'S 23°38.85'W 4871.2 CTD/rosette water sampler Abundance PS71/191-3 17.03.08 10:32 67°20.95'S 23°38.21'W 4871.7 CTD, Ultra Clean Abundance P571/193-6 18.03.08 20:30 66°36.44'S 27°9.39'W 4864.7 CTD, Ultra Clean Bacterial PS7I/193-10 19.03.08 11:44 66°35.16'S 27°20.59'W 4863.5 CTD, Ultra Clean Preliminary results Flow cytomtery of the algal populations revealed that with increasing latitude there was a change in the composition of the phytoplankton community shifting away from a dominance of cyanobacteria towards picoeukaryote cells. In addition, overall abundance of the microbial community was observed to decrease. Preliminary interpretation of the dilution experiments indicated that prior to crossing the Polar Front, viral lysis was a significant factor in the control of the picophytoplankton community (Fig. 5.1). However, viral lysis was not detected on any of the stations examined after this point, indicating that viruses play only a minor role or are not implicated in the control of these polar communities. Whereas, significant rates of grazing were routinely recorded indicating that in the Southern Ocean herbivory is a major process controlling primary production. Further work will be needed to finalize this data set and it is expected that this will be completed by the end of 2008. Fig. 5.1: Growth grazing and viral lysis rate of the dominate components of picophytoplankton community as determined by preliminary interpretation of the dilution experiments. 5.2 Phytoplankton measurements Veronique Garcon, Marielle Lacombe CNRS/LEGOS, Toulouse Objectives The ocean is getting acidified in response to atmospheric CO2 increase. The impact of such an acidification on primary producers is usually investigated through laboratory experiments or coupled physical/biogeochemical modeling. What is the insitu state of the ocean with respect to pH conditions and distribution of the various phytoplanktonic groups? This knowledge is a prerequisite for both carrying out proper models outputs validation, and establishing the present state. We are interested in the Polar frontal region of Drake Passage by two major phytoplanktonic functional types: diatoms (siliceous phytoplankton) and coccolithophorids (calcareous phytoplankton). Our main objective is to investigate the relationship between the variations of acidification level (pH and alkalinity) and distribution of these two groups. Work at sea We have sampled across the Polar Front from the upper six Niskin bottles of all B1 CTD stations casts. Depths sampled were 10, 25, 50, 75, 100 and 150 m. Two liters (for pigments determination) and one liter sample (for phytoplankton speciation) were collected and then filtered on board right after in the cold container. Filters for pigments are stored in the -80°C freezer, membrane filters for speciation were dried at 50°C for a couple of hours and stored in a dry place. Duplicates were performed all along the section. A total of 27 CTD5 stations were sampled and 324 filters collected. All filters will be analyzed back in the laboratory for further determination of pigments composition by HPLC and for further identification and quantification of diatoms and coccol ithophorids biomass by microscopy. Expected results The distribution of the two phytoplanktonic groups will be established in the Polar Frontal region. By comparing with the pH and alkalinity conditions of the surface water masses, it will be possible to derive a relationship linking chemistry of seawater and the phytoplanktonic speciation. 6. AUTOMATIC DETECTION OF MARINE MAMMALS Olaf Boebel, Carmen Böning and Olaf Klatt Alfred-Wegener-Institut Objectives The automated detection of marine mammals has a broad range of applications. Population ecologists focussing on whale distributions and migratory patterns are interested in effective methods for conducting marine mammal censuses. Users of hydroacoustic instruments are interested in implementing reliable and effective mitigation methods in case adverse reactions of marine mammals are to be apprehended. Whales spend considerable periods of time at the surface as well as submerged. Diving, vocalizing mammals may be detected by passive sonar while surfaced whales might be recognized by means of their warm blow, which stands out against the cold Antarctic environment. The objectives of this cruises' projects were to: a) determine the range at which the new IR lenses are capable of detecting marine mammals; b) deploy and recover acoustic recorders (PODs and Aurals) for the detection of whale and seal vocalizations to be used in the context of environmental suitability models; c) test the technology and deployment procedure of a mobile, automated listening station, PALAOA-S. Work at sea Infrared Cameras Two infrared (IR) cameras and a visual camera, contained in protective housings are mounted in the crow's nest of Polarstern (Tab. 6.1). The cameras are oriented coaxially but view different angular segments due to different lenses. The IR cameras provide a resolution of 320 x 240 pixels with 25 frames per second. The visual camera operates at 640x480 pixels. The cameras are connected to two PCs in the scientific work room via an optical FireWire link. The image stream is displayed on the PCs and 10 second long snippets are stored every 3 minutes (typically) by the Matlab TM based programme WaiBlas. Tab. 6.1: Camera system configuration CAMERA label in video lense location ---------------------- -------------- ----- ------------------------- visual VIS 24° top (+04 m) FLIR ThermoVision A4OM CAM1 12° middle (28.5 above water) FLIR ThermoVision A4OV CAM3 7° bottom (-04 m) When preparing the system in Bremerhaven during Polarstern's docking time, a power supply cable for the A4OV camera was identified as broken. Temporal constraints prohibited an immediate exchange of this cable (which involves significant efforts to open and reseal two water tight feedthroughs). To solve this problem in the highly exposed area of the crow's nest prior to Polarstern's departure from Cape Town, two of us arrived early to use the time in port for an exchange of this cable. The work was finished successfully before Polarstern left port. The camera system was modified with regard to its previous configuration as to be able to rotate it in the horizontal to be able to point it in the direction of whales which might eventually be sighted visually. Generally, however, the system was fixed, pointing in the direction 100 starboard from the ships heading. Starting on 13 March 2008 the IR system was operated almost continuously for 360 hours, until 28 March 2008, generating some 80 GByte of video data. Interruptions resulted mainly from hang-ups of the video stream, all of which could simply be solved by rebooting the computer or cameras. On a daily basis, both IR cameras' video data of the previous day were searched manually for events such as whale blows, seals, icebergs or birds. Interesting events were noted in event log files. Data Loggers (PODs Aurals and PALAOA-S) During a previous expedition, ANT-XXII/3, three autonomous data loggers, PODs (Porpoise Detectors by Chledonia Inc.) had been deployed as part of 3 oceanographic deep sea moorings. The instruments were to record click events in the frequency bands around 9, 22, 41 and 70 kHz which most probably constitute the centre of frequency bands of echolocation clicks of toothed whales. The three devices were successfully recovered with the moorings after an operation period of over 3 years (Tab. 6.2). Tab. 6.2: Recovery of PODs POD Mooring Position Position Deployment Recovery Water POD ID ID Lat Lon Date Date Depth Depth ---- --------- --------- --------- ---------- ---------- ------ ------ A401 AWI 230-5 66°00.66' 00°11.28' 08.02.2005 08.03.2008 3450 m 1557 m S E 21:00 8:25 B402 AWI 233-7 69°23.60' 00°04.29' 17.02.2005 12.03.2008 1950 m 1700 m S W 21:06 14:54 0403 AWI 207-6 63°42.20' 50°52.22' 14.03.2005 pending 2500 m 1457 m S W 02:47 While PODs are designed to record the high frequency clicks of odontocetes, many marine mammals vocalize in the 10 Hz to 20 kHz range. Detection and identification of such vocalizations requires broadband audio recordings. To complement such recordings from the PALAOA listening station north of Neumayer (Boebel et al., 2008), two underwater recorders (AURAL-M2 by Multi Electronique, Canada) and a PALAOA-S (Satellite) listening station were deployed (Tab. 6.3). The two Aural-M2s are incorporated in oceanographic deep sea moorings and are programmed to record the first 5 minutes out of sound every 4 hours (starting at midnight of each day). Tests prior to deployment however showed that the system will skip every 48th record (i.e. the last record of every 8th day). By contrast, PALAOA-S is designed to collect continuous sound records, but for a period of one day only. In a first sea-trial (that is in open waters), PALAOA-S was placed on an ice floe of about 2 m freeboard, close to the ice shelf edge in the southwestern corner of Atka Bay. The hydrophone was lowered over the floe's edge into the water to a depth of an estimated 5 m. During the course of the day, the floe drifted seawards with the prevailing wind driven and tidal currents away from the ice shelf edge. Upon recovery during the next day, PALAOA-S had drifted some 366 nm, to a location east of Polarstern's berthing site at the ice shelf (70°34.12'S, 008°08.21'W). Tab. 6.3: Deployments of Aural-M2s and PALAOA-S. For the PALAOA-S deployment, the top row indicates the deployment position, the bottom row the recovery position. ID Mooring Position Position deployment date water instrument ID Lat Lon depth depth ------- ---------- ---------- ----------- ---------------- ------ ---------- 70°37.70'S 008°08.19'W 02.03.2008 08:35 PALAOA-S - 70°34.08'S 008°08.23'W 03.03.2008 10:20 ~200 m 5 m #086 AWI 230-6 66°01.13'S 00°04.77'E 08.03.2008 3450 m 189 m #085 AWI 232-9 68°59.74'S 00°00.17'E 11.03.2008 3370 m 206 m Figure 6.1: Positions of AURAL deployments (yellow) and POD recoveries (black). A red diamond indicates the position of the PALAOA station and the two-day deployment of PALAOA-S (at a distance of approximately 6 miles to PALAOA). Preliminary and expected results Infrared Cameras While unobserved (i.e. not directed manually towards a sighted whale), the system recorded a few whale blows, seals and birds simply by chance, as records are taken in limited angular segments and only every 10s out of 3 minutes. On 15 March 2008, several whales were observed swimming ahead of the ship while following a lead through the ice. Then, the camera system was pointed manually towards the lead and whales. In this way, 15 whale blow events were recorded. A similar event occurred on 24 March 2008 with Polarstern on station and whales present in a lead portside-astern of the ship. Overall, the 12° camera recorded 27 snippets showing blowing whales (as identified by manually browsing the data), while the 7° camera recorded 10 blows. These whales were identified as Minke whales. Earlier experiences had showed that Minke whales are difficult to detect with a 24° lense due to their tendency to keep some distance from the ship and their relatively small and faint blow. However, the new high resolution (7° and 12°) lenses clearly revealed the blows, even at a distance of order 1 km (Fig. 6.2). The distance d between the ship and an event (at the sea surface) was estimated from the number of pixels N, between the horizon and the event, avoiding detailed knowledge of the cameras orientation (including the ship's pitch, roll and heave). ⎛ ⎛r(H)⎞ ⎞ d = h · tan⎜arctan⎜----⎟-N · φ⎟ ⎝ ⎝ h ⎠ ⎠ ____________ and rH = √2r(E)h+h(^2) i.e. the distance to the horizon as a function of camera height h~ 28.5 m, r(E) the earth radius, and φ the instant field of view (or angular segment of a single pixel). Errors are estimated by assuming an uncertainty in the camera height of ± 1 m. Analysis of the images showed, that seals and whale blows are detectable up to distance of 1.5 km with both the 12° and 7° lenses. Fig. 6.2: IR images by FL/A Thermacam A4OM with 12° lense prior (left) and during peak (right) of Minke whale blow. The image to the right was taken 0.24 s after image to the left. The blow was visible for the duration of 8 frames, which corresponds to about 0.56 s. The distance to the blow is estimated to be 1164 ±40 m. Dark areas are covered by sea ice, brighter areas represent (partially) open water. Fig. 6.3: Infrared images showing a group of seals in the far distance. Left: IR CAM1 with 12° lense, the distance is estimated to 1590.4:t 53 m. Right IR camera with 7°, the distance is estimated to 1588.9 ± 53 m. Further analysis will use the collected set of IR snippets to further develop automatic pattern recognition algorithm while avoiding false positives. Data Loggers (PODs, Aurals, and PALAOA-S) The recovered three PODs appear to be in good shape and are internally dry, even though this was the first deployment of such instruments at depths greater than 1500 m. The data will however only be accessible in Bremerhaven. Until then the instruments are stored upside down in "idle" mode. Both pressure cases of the new Aural units have been successfully tested to a depth of 300 m prior to the instruments deployment at around 200 m depth. The deployment of PALAOA-S proceeded without complications, though it is advisable to mark every 1 m of the hydrophone cable to be able to estimate the deployment depth in the field. The collected acoustic data will be analysed in Bremerhaven in conjunction with recording from PALAOA. References Boebel, O., Kindermann, L., Klinck, H., Bornemann, H., Plötz, J., Steinhage, D., Riedel, S., Burkhardt, E.(2006).Acoustic Observatory Provides Real-Time Underwater Sounds from the Antarctic Ocean, EOS, 87, 361-372. 7. WEATHER SITUATION DURING THE CRUISE LEG ANT-XXIV/3 Wolfgang Seifert and Klaus Bult Deutscher Wetterdienst Between 5 and 9 February a strong south-easterly gale situation, well known as "Cape Doctor", influenced the Cape region. As a consequence the loading activities had to be postponed. This was one reason why Polarstern finally sat sail not before 10 February. After crossing the subtropical high we reached the Subtropical Front at 40°S with westerly winds force 6 Bft. During the following days several secondary lows as part of polar frontal system crossed our course with south-westerly gales force 8 - 9 Bft and waves up to 7 m (Fig. 7.1a). With the beginning of the following week the frontal zone developed in a more meridional shape with two dominant low pressure systems: an upper level trough with a surface low southwest of the Antarctic Peninsula and a steering low pressure system east of 30°E. Between these two systems especially close to the Greenwich meridian - our course track - a flat high pressure ridge developed and caused wind forces less than 5-6 Bft with wave heights under 2-3m (Fig. 7.1b). During the following days a new low developed near 20°W with secondary lows moving from its northern flank southeast, where theses systems came in a slow dipolar rotation. Firstly, near the core afterwards on its southern flank Polarstern approached the ice shelf at Atka Bay on 2 March. During this day moderate winds were observed (Fig. 7.lc and Fig. 71d). At this morning a helicopter accident happened in good flight conditions as described in a special report(1). --------------------------------- (1) Report about weather conditions on the occasion of a flight accident for LBA On 5 March Polarstern left the Atka region in fair weather conditions. During the following days two polar lows influenced our course with stormy weather of wind force 8 - 9 Bft and increasing waves of about 4 m. This was observed several times during the expedition when a cold upper low produced some vorticity centres with sheering wind systems at the surface (Fig. 7.2a). Operating along the Greenwich meridian again Polarstern sailed at the western flank of a dominant low east of 15°E with mostly south-eastern winds forces 6 - 7 Bft (Fig. 72b). By 13 March, we headed west through the Weddell Sea. New low pressure systems north and northeast of our track showed that we were on the cold side of the frontal zone with mostly southerly or south-easterly winds force 6 - 7 Bft (Fig. 72c). Sailing along the northern ice edge weather improved temporarily. After 18 March a new low pressure system moved from northwest in south-eastern direction and caused winds from northeast to east up to force 7 Bft. Without the shelter of the ice the ship would have experienced the effect of higher waves (Fig. 7.2d). The circulation changed during the following days because of a more unstable frontal zone with an increasing wave number from 4 to 5. That's why a new cyclone could establish close to 65°N and 30°W with a secondary low moving on its eastern flank southwards. Polarstern was affected by several trough centres which caused surface lows with wind forces 7 - 9 Bft. However waves only increased up to 3 m because of the short fetch. At the western side of this system mainly southerly to southeasterly winds with force 5 - 7 Bft prevailed but the pacific system developed secondary lows near the northern part of the Antarctic Peninsula so that Polarstern was influenced some days by easterly to north-easterly winds which affected a compression of the northern ice edge (Fig. 7.3a). On 30 March Polarstern approached Jubany Station as scheduled. By then moderate winds were observed. Because of strong windward-effects at the South-Shetlands the cloud base lowered to 300 ft and fog prevailed at times with strong variations of visibility and cloud base. Nevertheless most of the planned flight operations could be done. However, the flight to Artigas Station (Uruguay) had to be cancelled dew to impossible flight conditions with a cloud base of 100 ft and visibility under 300 m. Polarstern left King George Island in the afternoon of 31 March heading northeast. During the following days we reached the frontal zone between two dominant long wave systems in an area between 100°W und east of 45°W (Fig. 73b). The wind situation then was relatively moderate with an average wind force of about Bft 6 - 7. Only occasionally westerly storms with force 8 - 9 Bft were observed. Because of the relatively long fetch the sea state was more influenced by swell than by wind sea with significant heights up to 4 m. In the beginning of the two last weeks at sea Polarstern sailed at the southern flank of a low pressure zone reaching from the Bellingshausen Sea to the Malvinas and South Georgia (Fig. 73c). Therefore the predominant wind direction was northeast with wind speed about 20 kn. This situation remained until 13 April while the ship was heading towards Cabo San Diego. At the end of the research operations on 14 April the frontal zone established and intensified from the eastern Pacific to southern Patagonia (Fig. 7.3d). On board Polarstern a strong wind field from southwest with force up to 8 - 9 Bft and waves up to 5 m were observed. The last two days in lee of the continent were not influenced by any meteorological event so that Polarstern arrived at Punta Arenas on 16 April as scheduled. Fig. 7.1: Sea surface and air pressure distribution for the periods a: 10 - 17 Feb 2008 b: 18 - 22 Feb 2008 c: 23 - 27 Feb 2008 d: 28 - 03 Mar 2008 Fig. 7.2: Sea surface and air pressure distribution for the periods a: 04 - 08 Mar 2008 b: 09 - 12 Feb 2008 c: 13 - 17 Feb 2008 d: 18 - 23 Mar 2008 Fig. 7.3: Sea surface and air pressure distribution for the periods a: 24 - 28 Mar 2008 b: 29 - 04 Apr 2008 c: 05 - 09 Apr 2008 d: 10 - 14 Apr 2008 8. ACKNOWLEDGEMENT ANT-XXVII/3 was the most difficult cruise for all of us. In the course of the helicopter accident on 2 March 2008 two cruise participants lost their lives and three were injured so that they had to be evacuated. Although overshadowed by that dramatic event, we were able to collect extensive data sets and outstanding samples during that cruise and we achieved our logistic tasks. This was a further proof of the exceptional professionalism and the never ending commitment of the Polarstern crew. For that we would like to express our heartfelt and sincere thanks to Master Schwarze and his entire crew. We want to thank as well all those, even if we are not able to state them all by name, who contributed to the success of the cruise by their support on shore during planning, preparation and while we had been at sea. APPENDIX A.1 PARTICIPATING INSTITUTIONS A.2 CRUISE PARTICIPANTS A.3 SHIP'S CREW A.4 STATION LIST PS71 A.1 BETEILIGTE INSTITUTE/ PARTICIPATING INSTITUTES ANT-XXIV/3 Adresse Address ------------------------------------------------------------------------------ AWI Alfred-Wegener-Institut für Polar- und Meeresforschung in der Helmholtz-Gemeinschaft Am Handelshafen 12 27570 Bremerhaven / Germany CNRS LEGOS LEGOS Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales Unite Mixte de Recherche CNRS, UPS, CNES, IRD 18 avenue Edouard Behn 31055 Toulouse / France DESE Dept. of Earth Science & Engineering Imperial College London SW7 2AZ / UK (participating, but not on cruise) DWD Deutscher Wetterdienst Geschäftsbereich Wettervorhersage Seeschifffahrtsberatung Bernhard Nocht Str. 76 20359 Hamburg /Germany Heli Service Heli Service International GmbH Im Geisbaum 2 63329 Egelsbach / Germany IFM-GEOMAR Leibniz-Institut für Meereswissenschaften IFM- GEOMAR Düsternbrooker Weg 20 24105 Kiel / Germany IGM Institut für Geologie und Mineralogie Universität zu Köln Zülpicher Strasse 49 a/b 50674 Köln / Germany IUP Institut für Umweltphysik (IUP) Ozeanographie Institute of Environmental Physics Oceanography Otto-Hahn-Allee 1 D-28359 Bremen I Germany KORDI Korean Ocean Research and Development Institute 1270 Sa-dong Sangrok-gu, Asan Kyunggi-do P0 Box 29 425-600 Korea Laeisz Reederei F. Laeisz (Bremerhaven) GmbH Brückenstrasse 25 27568 Bremerhaven I Germany LEMAR Laboratoire des Sciences de lEnvironnement Mann (LEMAR), CNRS-UMR 6539 Institut Universitaire Européen de la Mer (IUEM) Technopole Brest-Iroise Place Nicolas Copernic 29280 Plouzané I France LOCEAN LOCEAN (Laboratoire d'Oceanographie et du Cl imat: Experimentation et Analyses N umeriques) Unite Mixte de Recherche CNRS, UPMC, MNHN, IRD Université Pierre et Marie Curie Tour 45-55 5E 4 place Jussieu 75252 Paris cedex 05 I France LSCE Laboratoire des Sciences du Climat et de lEnvironnement / Institut Pierre Simon Laplace Domaine du CNRS Bat 12 - avenue de la Terrasse F - 91198 Gif-sur-Yvette Cedex I France MPI Chemie Max- Planck- lnstitut für Chemie Abteilung Geochemie Postfach 3060 55020 Mainz / Germany NIOZ Koninklijk Nederlands lnstituut vor Onderzoek der Zee Department for Marine Chemistry and Geology P.O. Box 59 1790 AB Den Burg I The Netherlands OPTIMARE OPTIMARE Am Luneort 15a 27572 Bremerhaven I Germany RMfCA Section of Mineralogy and Geochemistry Department of Geology Royal Museum for Central Africa Leuvensesteenweg, 13 B-3080 Tervuren I Belgium University Brussels Vrije Universiteit Brussel Analytical and Environmental Chemistry Pleinlaan 2 B-1050 Brussels I Belgium University Las Palmas Departamento de QuImica Universidad de Las Palmas de Gran Canaria Campus de Tafira 35017 Las Palmas /Spain University Liege Chemical Oceanography Unit Astrophysics, Geophysics and Oceanography Department Université de Liege, Belgium Allee du 6 Aoüt, 17 4000 Liege I Belgium University of Groningen Faculteit Wiskunde en Natuurwetenschappen University of Groningen Nijenborgh 4 9747 AG Groningen I The Netherlands XU XU Research Center for Environmental Science Xiamen University Xiamen 361005 I China A.2 FAHRTTEILNEHMER/ PARTICIPANTS Name/ Vorname/ Institut/ Beruf/ Last name First name Institute Profession ------------ ------------- ------------ --------------------------- ----------- Alderkamp An ne-Carlijn University Biologist of Groningen Baars Oliver IFM-GEOMAR PhD student, geochemistry Beauverger Mickael LOCEAN Engineer, oceanography From K.G.I. Bluhm Katrin IFM-GEOMAR PhD student, biology Boebel Olaf AWI Physicist Boening Carmen AWI PhD student, oceanography Bontes Babette NIOZ PhD student, biology Bult Klaus DWD Technician, weather station Cai Pinghe XU Geochemist Cristini Luisa AWI Physicist Croot Peter IFM-GEOMAR Marine chemist de Baar Hein NIOZ Geochemist Evans Claire NIOZ Biologist Fahrbach Eberhard AWI Oceanographer Frijling Erwin NIOZ Chemist Garcon Veronique CNRS LEGOS Oceanographer From K.G.I. Gebler Madlen IUP Student, physics Gerringa Loes NIOZ Chemist Gremlowski Lars AWI Student, chemistry Gronholz Alexandra IUP Student, physics Heckmann Hans-Hilmar HeliService Pilot Heller Maija IFM-GEOMAR PhD student, chemistry Huhn Oliver IUP Physicist Hwang San Chui KORDI Oceanographer From K.G.I. Kartavsteff Annie LOCEAN Engineer, oceanography From K.G.I. Klatt Olaf AWI Physicist Laan Patrick NIOZ Engineer, chemistry Lacombe Marielle CNRS LEGOS PhD student, oceanography Lee Jae-Hak KORDI Oceanographer From K.G.I. Legoff Hervé LOCEAN Engineer, oceanography From K.G.I. Lohse Charlotte IPY teacher Teacher programme Middag Rob NIOZ PhD student, biology/geochemistry Monglon Thierry LOCEAN Technician, oceanography From K.G.I. Monsees Matthias OPTIMARE Technician, oceanography Neven Ika University PhD student, geochemistry Groningen Nunez-Ribuni Ismael AWI Physicist Ober Sven NIOZ Engineer, chemistry Paz Martinez Andrea Observer From K.G.I. Provost Christine LOCEAN Oceanographer From K.G.I. Robert Maya AWI PhD student, biology Rohardt Gerd AWI Oceanographer Sander Hendrik OPTIMARE Physicist Seifert Wolfgang DWD Meteorologist Sennechael Nathalie LOCEAN Oceanographer From K.G.I. Slagter Hans NIOZ MSc student, chemistry Spadone Aurelie LOCEAN PhD student, oceanography Stichel Torben IFM-GEOMAR PhD student, geochemistry Stimac Mihael HeliService Helicopter mechanic Strothmann Olaf AWI Technician, oceanography Sudre Joel LEGOS Engineer, oceanography Sweet Elisabeth AWI PhD student, geochemistry Theisen Stefan IPY teacher Teacher programme Thuroczy Charles- NIOZ PhD student, geochemistry Edouard Van Heuven Steven NIOZ PhD student, biology Van Ooijen Jan NIOZ Engineer, chemistry Van Slooten Cornelis NIOZ PhD student, biology Venchiarutti Celia AWI Chemist Stimac Ingrid AWI Technician, chemistry Two cruise participants lost their lives during the helicopter accident on 2 March 2008: Willem Polman, NIOZ, Technician, geochemistry Stefan Winter, HeliService, Pilot Three cruise participants had to return home from Neumayer station after being injured during the helicopter accident on 2 March 2008: Martin Klunder, NIOZ, PhD student, geochemistry Carsten Möllendorf, HeliService, Helicopter mechanic Alice Renault, LOCEAN, PhD student, oceanography A.3 SCHIFFSBESATZUNG / SHIP'S CREW No. Name Rank --- --------------------------- --------------------- 1. Schwarze, Stefan Master 2. Spielke, Steffen 1.Offc. from Neumayer 3. Fallei, Holger 1.Offc to Neumayer 4. Farysch, Bernd Ch.Eng. 5. Becker, lilo 2.Offc. 6. Peine Lutz 2.Offc. 7. Dugge, Heike 3.Offc. 8. Sokoll, Herbert Doctor 9. Hecht, Andreas R.Offc 10. Minzlaff, Hans-Ulrich 2.Eng. 11. Sümnicht, Stefan 2.Eng. 12. Schäfer, Marc 3.Eng. 13. Scholz, Manfred Elec.Tech. 14. Fröb Martin Electron. 15. Himmel, Frank Electron. 16. Muhle, Helmut Electron. 17. Nasis, Ilias Electron. 18. Loidl, Reiner Boatsw. 19. Reise, Lutz Carpenter 20. Bäcker, Andreas A. B. 21. Guse, Hartmut A. B. 22. Hagemann, Manfred A. B. 23. Schmidt, Uwe A. B. 24. Stutz, Hein-Werner A. B. 25. Vehlow, Ringo A. B. 26. Wende, Uwe A. B. 27. Winkler, Michael A. B. 28. Preußner, Uwe Storekeep. 29. EIsner, Klaus Mot-man 30. Hartmann, Ernst-Uwe Mot-man 31. Ipsen, Michael Mot-man 32. Pinske, Lutz Mot-man 33. Voy, Bernd Mot-man 34. Müller-Homburg, Ralf-Dieter Cook 35. Martens, Michael Cooksmate 36. Silinski, Frank Cooksmate 37. 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Shiller, Determination of Subnanomolar Levels of Hydrogen Peroxide in Seawater by Reagent-Injection Chem ilum inescence Detection, Analytical Chemistry, 71, 1975-1980, 1999. Yuan, J., and A.M. Shiller, The distribution of hydrogen peroxide in the southern and central Atlantic ocean, Deep-Sea Research II, 48, 2947-2970, 2001. Zhang, H., van den Berg, C.M.G. and Wollast, R., 1990. The Determination of Interactions of Cobalt(II) with Organic Compounds in Seawater using Cathodic Stripping Voltammetry. Marine Chemistry, 28: 285-300. CCHDO DATA PROCESSING NOTES Date Person Data Type Action Summary ---------- ----------- ---------- -------------- --------------------------- 2012-07-26 Bob Key CTD/CrsRpt Submitted to go online CTD data file for ANT XXIV/3. This is another of the PANGAEA format files. I'm working with German partners on the bottle file. Have requested final version of the cruise report 2012-09-07 CCHDO Staff CTD Website Update Available under 'Files as received' The following files are now available online under 'Files as received', unprocessed by the CCHDO. ANT-24-3-cruise-report_PRELIM.pdf ANT-XXIV_3_phys_oce.tab.tsv 2012-09-25 J Kappa CrsRpt Submitted pdf and text versions I've placed 2 new versions of the cruise report: a12_06AQ20080210do.pdf a12_06AQ20080210do.txt into the co2clivar/atlantic/a12/a12_06AQ20080210/directory. Both docs include summary pages and CCHDO data processing notes. The pdf version also includes a linked Table of Contents and links to figures, tables and appendices. Both will be available on the cchdo website following the next update script run. 2013-03-15 Bob Key CrsRpt Submitted to go online Detailed Notes Today I'm uploading the final cruise report. Previous version of report was Prelim. Filename is Fah2010a.pdf Steven van Heuven has provided me with a final (but incomplete) version of the bottle data. In the next few days I'll translate flags (from ODV) and reformat. If you could reformat the CTD data we can finish this one up in short time. As a separate chore I'll try to obtain the missing isotope data, but we shouldn't wait for that. 2013-03-19 CCHDO Staff CrsRpt Website Update Available under 'Files as received' Detailed Notes The following files are now available online under 'Files as received', unprocessed by the CCHDO. Fah2010a.pdf 2013-03-19 Bob Key BTL Submitted to go online Detailed Notes This is an updated version of the file I previously uploaded for this cruise. There are numerous minor error fixes and all of the included parameters are "final". Still expected are CFC and H3/He data from Bremen. I sent a request for these data earlier today, but expect they will be proprietary for awhile yet. This file completes my work on this cruise until those data are received. This file should simply replace (rather than parameter update) previous submission. The full parameter set will be available at BODC as a GEOTRACES file. Given this the previous e-mail regarding BCO=DMO submission an U/Th isotopes is now moot. 2013-03-19 CCHDO Staff BTL Website Update Available under 'Files as received' Detailed Notes The following files are now available online under 'Files as received', unprocessed by the CCHDO. 06AQ20080210.exc.csv 2013-03-28 Bob Key CFCs Submitted to go online Detailed Notes This file is the same as the other recently submitted version except that this contains the CFC data and the header has been modified accordingly. Oliver Huhn and Monika also supplied an addition for the cruise report (also attached). 2013-03-29 CCHDO Staff CFCs Website Update Available under 'Files as received' Detailed Notes The following files are now available online under 'Files as received', unprocessed by the CCHDO. 06AQ20080210.exc.csv readme_ant24_3_tracer_ohuhn_IUP_bremen_germany.pdf 2013-04-05 Bob Key BTL Submitted edited header, includes He data Detailed Notes This is the same file I uploaded on 3/28/13 except that the header has been edited and the He data from Huhn & Rhein have been added. BCO-DMO will (does?) have a different version of this file that will include trace metals, biologicals, partical isotopes, etc. 2013-04-05 Bob Key CrsRpt Submitted CFC report to be added to CrsRpt 2013-04-08 CCHDO Staff BTL Website Update Available under 'Files as received' Detailed Notes The following files are now available online under 'Files as received', unprocessed by the CCHDO. 06AQ20080210.exc.csv 2013-04-08 CCHDO Staff CrsRpt Website Update Available under 'Files as received' Detailed Notes The following files are now available online under 'Files as received', unprocessed by the CCHDO. readme_ant24_3_tracer_ohuhn_IUP_bremen_germany.pdf 2013-04-17 Jerry Kappa CrsRpt Website Update Final pdf version online Detailed Notes The final pdf version of the cruise report is now online. Updates include: • Final cruise report • Final CFC report • Updated/expanded data processing notes • CCHDO-generated station track figure Corrections: • Table 3.2, p146 truncated (right hand column missing). Replaced with same table from preliminary report. • Step 2, p. 80 formula missing. Copied formula from preliminary report • Step 2, p. 81 formula missing. Copied formula from preliminary report • Step 1, p. 82 formula missing. Copied formula from preliminary report 2013-04-17 Jerry Kappa CrsRpt Website Update Final text version online Detailed Notes The final text version of the cruise report is now online. Updates include: • Final cruise report • Final CFC report • Updated/expanded data processing notes