TO VIEW PROPERLY YOU MAY NEED TO SET YOUR BROWSER'S CHARACTER ENCODING TO UNICODE 8 OR 16 AND USE YOUR BACK BUTTON TO RE-LOAD CRUISE REPORT: AR24 (Updated: AUG 2008) A. HIGHLIGHTS A.1. WHP Cruise Summary Information WOCE section designation AR24 Expedition designation (EXPOCODE) 316N147_2 Chief Scientist Dr. Michael McCartney/WHOI Dates 1996 NOV 02 - 1996 DEC 05 Ship R/V KNORR Ports of call Ponta Delgada, Azores 64° 54.17' N Stations' geographic boundaries 43°29.67' W 11°10.12' W 39°8.17' N Number of stations 190 Floats and drifters deployed 0 Moorings deployed or recovered 0 Chief Scientist Contact Information Dr. Michael McCartney Department of Physical Oceanography • Woods Hole Oceanographic Institution Clark 344 • Woods Hole, MA • 02543 Phone: 508-289-2797 • Fax: 508-457-2181 • email: mike@gaff.whoi.edu ORNL/CDIAC-143 NDP-082 CARBON DIOXIDE, HYDROGRAPHIC, AND CHEMICAL DATA OBTAINED DURING THE R/V KNORR CRUISES IN THE NORTH ATLANTIC OCEAN ON WOCE SECTIONS AR24 (NOVEMBER 2 - DECEMBER 5, 1996) AND A24, A20, AND A22(MAY 30 - SEPTEMBER 3, 1997) Contributed by Kenneth M. Johnson,1 Robert M. Key,2 Frank J. Millero,3 Christopher L. Sabine,4 Douglas W. R. Wallace,5 Christopher D. Winn,6 Linda Arlen,7 Kenneth Erickson,8 Karsten Friis,5 Meridith Galanter,3 Jamie Goen,3 Richard Rotter,2 Carrie Thomas,2 Richard Wilke,8 Taro Takahashi,9 Stewart C. Sutherland9 1 Department of Applied Science, Brookhaven National Laboratory, Upton, NY, U.S.A. Retired, now at P.O. Box 483, Wyoming, RI, U.S.A. 2 Department of Geosciences, Princeton University, Princeton, NJ, U.S.A. 3 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, U.S.A. 4 Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, U.S.A. 5 Institute for Marine Sciences, Kiel, Germany 6 Hawaii Pacific University, Kaneohe, HI, U.S.A. 7 James J. Howard Laboratory, NOAA, Sandy Hook, NJ, U.S.A. 8 Department of Applied Science, Brookhaven National Laboratory, Upton, NY, U.S.A. 9 Lamont-Doherty Earth Observatory, Palisades, NY, U.S.A. Prepared by Alexander Kozyr Carbon Dioxide Information Analysis Center Oak Ridge National Laboratory Oak Ridge, Tennessee, U.S.A. Date Published: September 2003 Prepared for the Climate Change Research Division Office of Biological and Environmental Research U.S. Department of Energy Prepared by the Carbon Dioxide Information Analysis Center OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37831-6335 Budget Activity Numbers: KP 12 04 01 0 and KP 12 02 03 0 managed by UT-BATTELLE, LLC for the U.S. DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725 ORNL/CDIAC-143 NDP-082 ACRONYMS ACCE Atlantic Circulation and NDP numeric data package Climate Change Experiment NOAA National Oceanic and A/D analog-to-digital Atmospheric Administration ADCP acoustic Doppler current nm nautical mile profiler NSF National Science Foundation ALACE autonomous Lagrangian ODF Ocean Data Facility circulation explorer ODV Ocean Data View BOD biological oxygen demand ORNL Oak Ridge National Laboratory BNL Brookhaven National Laboratory OSU Oregon State University 14C radiocarbon PC personal computer CALFAC calibration factor PDF Portable Document Format CDIAC Carbon Dioxide Information PI principal investigator Analysis Center PU Princeton University CFC chlorofluorocarbon QA quality assurance CMDL Climate Monitoring and QC quality control Diagnostics Laboratory R/V research vessel CO2 carbon dioxide RSMAS Rosenstiel School of Marine CTD conductivity, temperature, and and Atmospheric Sciences depth sensor SIO Scripps Institution of CRM certified reference material Oceanography DOE U.S. Department of Energy SOMMA single-operator multipara- emf electro-magnetic fields meter metabolic analyzer EXPOCODE expedition code SSW standard seawater FTP file transfer protocol TALK total alkalinity GMT Greenwich mean time TCO2 total carbon dioxide GPS global positioning system TD to-deliver IAPSO International Association for the UH University of Hawaii Physical Sciences of the Ocean UM University of Miami I/O input-output UW University of Washington IR infrared VFC voltage to frequency converter JGOFS Joint Global Ocean Flux Study WHOI Woods Hole Oceanographic kn knots Institution LADCP lowered ADCP WHPO WOCE Hydrographic Program LDEO Lamont-Doherty Earth Office Observatory WOCE World Ocean Circulation MATS Miami University alkalinity Experiment titration systems WHP WOCE Hydrographic Program NBIS Neil Brown Instrument system ABSTRACT Johnson K., R. Key, F. Millero, C. Sabine, D. Wallace, C. Winn, L. Arlen, K. Erickson, K. Friis, M. Galanter, J. Goen, R. Rotter, C. Thomas, R. Wilke, T. Takahashi, and S. Sutherland. 2003. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Knorr Cruises in the North Atlantic Ocean on WOCE Sections AR24 (November 2-December 5, 1996) and A24, A20, and A22 (May 30-September 3, 1997) A. Kozyr (ed.) ORNL/CDIAC-143, NDP-082. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, 41 pp. This documentation describes the procedures and methods used to measure total carbon dioxide (TCO2) total alkalinity (TALK), and partial pressure of CO2 (pCO2) at hydrographic stations on the North Atlantic Ocean sections AR24, A24, A20, and A22 during the R/V Knorr Cruises 147-2, 151-2, 151-3, and 151-4 in 1996 and 1997. Conducted as part of the World Ocean Circulation Experiment (WOCE), the expeditions began at Woods Hole, Massachusetts, on October 24, 1996, and ended at Woods Hole on September 3, 1997. Instructions for accessing the data are provided. A total of 5,614 water samples were analyzed for discrete TCO2 using two single-operator multiparameter metabolic analyzers (SOMMAs) coupled to a coulometer for extracting and detecting CO2. The overall accuracy of the TCO2 determination was ± 1.59 µmol/kg. The TALK was determined in a total of 6,088 discrete samples on all sections by potentiometric titration using an automated titration system developed at the University of Miami. The accuracy of the TALK determination was ± 3 µmol/kg. A total of 2,465 discrete water samples were collected for determination of pCO2 in seawater on sections A24, A20, and A22. The pCO2 was measured by means of an equilibrator-IR system by scientists from Lamont-Doherty Earth Observatory. The precision of the measurements was estimated to be about ± 0.15%, based on the reproducibility of the replicate equilibrations on a single hydrographic station. The North Atlantic data set is available as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of 12 ASCII data files, one Ocean Data View-formatted data file, a NDP-082 ASCII text file, a NDP-082 PDF file, and this printed documentation, which describes the contents and format of all files, as well as the procedures and methods used to obtain the data. Keywords: carbon dioxide; TCO2; total alkalinity; partial pressure of CO2; coulometry; gas chromatography; World Ocean Circulation Experiment; North Atlantic Ocean; hydrographic measurements; carbon cycle. 1. BACKGROUND INFORMATION The World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) was a major component of the World Climate Research Program. The primary WOCE goal was to understand the general circulation of the global ocean well enough to be able to model its present state and predict its evolution in relation to long- term changes in the atmosphere. The impetus for the carbon system measurements arose from concern over the rising atmospheric concentrations of carbon dioxide (CO2). Increasing atmospheric CO2 may intensify the earths natural greenhouse effect and alter the global climate. Although CO2-related measurements [total CO2 (TCO2), total alkalinity (TALK), partial pressure of CO2 (pCO2), and pH] were not an official WOCE measurements, a coordinated effort to make the carbon measurements was supported as a core component of the Joint Global Ocean Flux Study (JGOFS). This effort received support in the United States from the U.S. Department of Energy (DOE), the National Oceanic and Atmospheric Administration (NOAA), and the National Science Foundation (NSF) for WOCE cruises through 1998 to measure the global spatial and temporal distributions of CO2 and related parameters. Goals were to estimate the meridional transport of inorganic carbon in a manner analogous to the oceanic heat transport (Bryden and Hall 1980; Brewer, Goyet, and Drysen 1989; Holfort et al. 1998; Roemmich and Wunsch 1985), and to build a data base suitable for carbon-cycle modeling and the estimation of anthropogenic CO2 increase in the oceans. The CO2 survey took advantage of the sampling opportunities provided by the WOCE cruises during this period, and the final data set was expected to cover on the order of 23,000 stations. Wallace (2002) recently reviewed the goals, conduct, and initial findings of the survey. This report discusses the results of the research vessel (R/V) Knorr expedition along the WOCE Sections AR24, A24, A20, and A22 [cruises 147-2, 151-2, 151-3, and 151-4, respectively (Fig. 1)]. The latter three cruises not only were part of WOCE but also were a component of the Atlantic Circulation and Climate Change Experiment (ACCE). The ACCE was intended to improve the understanding of the entrainment and transformation of warm saline subtropical water into the subpolar North Atlantic waters, with special emphasis on sampling the North Atlantic Current region. This region plays an important role in the exchange of CO2 between the subtropical and subpolar gyres. The exchange between these gyres affects the magnitude and direction of air-sea CO2 exchange in the North Atlantic and is therefore an important factor in the global carbon cycle. By 1997 the goal of high-quality measurements of chemical and physical parameters had been completed in all of the major oceans except the North Atlantic. Hence the cruises documented here also represent the concluding phase of the DOE- sponsored Global CO2 Survey. The expedition (section AR24) started at Woods Hole, Massachusetts, USA, on October 24, 1996, with a transit to the Azores; the station work began on November 2, 1996. The 1997 cruises started from Ponta Delgada, Azores, on May 30, 1997, and ended in Woods Hole on September 3, 1997, after stops in Halifax, N.S., Canada, and Port of Spain, Trinidad. The large-scale three-dimensional distribution of temperature, salinity, and chemical constituents, including the carbonate system parameters measured on these cruises (TCO2, and TALK on the AR24 section and TCO2, TALK, and pCO2 on A24, A20, and A22 sections), will be plotted using the data from these sections. Knowledge of these parameters and their initial conditions will enable researchers to determine heat and water transport, as well as carbon transport, which will contribute to the understanding of processes affecting climate change. The sections described in this report include WOCE Section A22, the only Caribbean transect of the WOCE program. In addition, the stations occupied on these cruises repeated some sections sampled in previous years during the International Geophysical Year during the 1950s. They also included measurements from the eastern subpolar gyre of source and overflow waters from the Labrador, Norwegian, Greenland, and Iceland Seas. They give good coverage of boundary currents, particularly the Deep Western Boundary Current; and repeating AR24 and A24 provides some insight into seasonal variation in the North Atlantic. This data documentation is the result of the cooperative efforts of chemical oceanographers from Brookhaven National Laboratory (BNL), the University of Hawaii (UH), Lamont-Doherty Earth Observatory (LDEO), and the University of Miamis Rosenstiel School of Atmospheric and Marine Science (RSMAS), U.S.A. The work aboard the R/V Knorr was supported by the U. S. Department of Energy under contract DE-ACO2-76CH00016 and DE-FG02-93ER61540. The authors are also especially grateful to the Sonderforschungsbereich 460 at the University of Kiel (Dr. F. Schott, Leader), funded by the Deutsche Forschungsgemeinschaft, for their support and assistance in completing the written documentation. 2. DESCRIPTION OF THE EXPEDITION 2.1 R/V Knorr: Technical Details and History The R/V Knorr, built in 1969 by the Defoe Shipbuilding Company in Bay City, Michigan, is owned by the U.S. Navy. It was turned over to the Woods Hole Oceanographic Institution (WHOI) in 1971 for operation under a charter agreement with the Office of Naval Research. It was named for E. R. Knorr, a hydrographic engineer and cartographer who in 1860 held the title of Senior Civilian and Chief Engineer Cartographer of the U.S. Navy Office. Its original length and beam were 245 and 46 ft, respectively. Beginning on February 6, 1989, it underwent a major midlife retrofit or jumbo-izing at the McDermott Shipyard in Amelia, Louisiana. A midsection was added to the ship to stretch its length by 34 ft, to 279 ft, and fore and aft azimuthing propulsion systems were added to make it one of the most maneuverable and stable ships in the oceanographic fleet. By the time it was returned to the Woods Hole Oceanographic InstitutionWHOI in late 1991, the retrofit had taken 32 months. The WOCE section P6 was the vessels first scientific cruise after the retrofitting. The R/V Knorr was designed for a wide range of oceanographic operations and possesses antiroll tanks and a strengthened bow for duty in icy waters. Like its sister ship, the R/V Melville, it is used for ocean research and routinely carries scientists from many different countries. Table 1 provides a list of technical characteristics of the R/V Knorr. Table 1. Technical characteristics of the R/V Knorr ________________________________________________________________________ Ship name: R/V Knorr Call sign: KCEJ Basic dimensions: Gross registered tonnage 2518 T Displacement 2958 LT Overall length 279 ft Beam 46 ft Draught (maximum) 16.5 ft Service speed 12 kn Maximum speed 14.5 kn Minimum speed 0.1 kn Main deck clear length 126 ft Personnel: Crew 24 Scientists 34 Main engine: 4 X Mak6M 322 = 4 X 1000 kW at 750 rpm Propulsion: Twin lips diesel-electric, azimuthing stern thrusters, 1500 SHP Bow thruster: Lips retractable azimuthing 900 SHP Fuel capacity: 160,500 gal Maximum cruise duration: 60 days (12,000 nm) Nautical equipment: Integrated navigation system Potable water generator 2 instrument hangars Winches: 1 heavy-duty trawl with 30,000 ft of 1/2 -in. wire 2 hydrographic, both with 30,000 ft of hydrowire Hydraulic cranes on the starboard side aft and midships Scientific storage space of 1,320 ft^2 Portable van space Machine shop Fume hoods Uninterruptible power supply Air conditioning Library/lounge 3680 ft^2 of laboratory space for multidisciplinary research ________________________________________________________________________ 2.2 The North Atlantic Ocean CO2 Survey Cruises Information 2.2.1 WOCE Section AR24 Ship name: R/V Knorr Expocode 316N147-2 Cruise/Leg: 147-2/A24R Ports of call: Ponta Delgada, The Azores Dates: November 2, 1996 - December 5, 1996 Funding support: DOE, NSF Chief scientist: Dr. Mike McCartney, WHOI Parameters measured, institution, and responsible Iinvestigators Parameter Institution Responsible investigators ---------------- ----------- -------------------------------------- CTD*, Salinity WHOI M. McCartney Nutrients WHOI M. McCartney Oxygen WHOI M. McCartney CFCs** SIO R. Weiss Tritium, helium LDEO P. Schlosser TCO2 UH/BNL R. Rotter, C. Winn, K. M. Johnson TALK RSMAS M. Galanter, J. Goen, F. Millero Underway pCO2 AOML R. Wanninkhof C14 PU R. Key, R. Rotter ADCP(3)/LADCP(4) UH E. Firing 2.2.2 WOCE Section A24 Ship Name R/V Knorr Expocode 316N151-2 Cruise / Leg 151-2/A24 Ports of call Ponta Delgado, St. Michael, Azores; Halifax, N.S., CAN Dates May 30, 1997 - July 5, 1997 Funding support DOE, NSF Chief Scientist Dr. Lynne Talley, SIO Parameters measured, institution, and responsible investigators Parameter Institution Responsible Iinvestigators ---------------- ----------- -------------------------------------- CTD, Ssalinity SIO L. Talley, F. Delahoyde, C. Mattson Nutrients SIO/ODF J. Swift, D. Masten, S. Becker Oxygen SIO/ODF J. Swift, J. Boaz CFCs SIO R. Weiss, F. Van Woy, M. Vollmer Tritium, helium LDEO P. Schlosser, D. Smith, S. Khatiwala TCO2 BNL D. Wallace, K. Johnson, L. Arlen TALK RSMAS F. Millero, M. Galanter, J. Goen pCO2, discrete LDEO T. Takahashi, A. Wilson Underway pCO2 SIO R. Weiss, F. Van Woy 14C PU R. Key, R. Rotter ADCP/LADCP UH E. Firing 2.2.3 WOCE Section A20 Ship Nname R/V Knorr Expocode 316N151_3 Cruise/leg 151-3/A20 Ports of call Halifax, N.S, Canada, Port of Spain, Trinidad Dates July 17, 1997 - August 10, 1997 Funding support DOE, NSF Chief Sscientist Dr. Robert Pickart, WHOI Parameters measured, institution, and responsible Iinvestigators Parameter Institution Responsible investigators ---------------- ----------- -------------------------------------- CTD, salinity WHOI R. Pickart, M. Swartz Nutrients OSU L. Gordon, J. Jennings, B. Sullivan Oxygen WHOI R. Pickart CFCs LDEO W. Smethie, E. Gorman, L. Baker, D. Chaky Tritium, He WHOI W. Jenkins, P. Landry, S. Birdwhiste TCO2 BNL D. Wallace, R. Wilke, K. Erickson, K. M. Johnson pCO2, discrete LDEO T. Takahashi, J. Goddard TALK RSMAS F. Millero, C. Sabine, C. Thomas Underway pCO2 SIO R. Weiss 14C PU R. Key, C. Sabine, C. Thomas Bio-Ooptics LDEO C. Knudson Halocarbons DU R. Moore, P. Morneau, W. Groszko ADCP/LADCP WHOI D. Torres ALACE(5) floats UW D. Swift 2.2.4 WOCE Section A22 Ship Nname Knorr Expocode 315N151_4 Cruise/leg 151-4/A22) Ports of call Port of Spain, Trinidad; Woods Hole, MA, USA Dates August 15, 1997 - September 3, 1997 CO2 Funding DOE, NSF support Chief Sscientist Dr. Terrence Joyce, WHOI Parameters measured, institution, and responsible Iinvestigators Parameter Institution Responsible investigator -------------- ----------- -------------------------------------- CTD, salinity WHOI T. Joyce, G. Knapp, L. Stein Nutrients OSU L. Gordon, A. Ross, J. Arrington Oxygen WHOI G. Knapp, D. Wellwood CFC's LDEO W. Smethie, L. Baker, D. Chaky, E. Gorman, R. Swartz Tritium, He WHOI W. Jenkins, J. Curtis, P. Landry TCO2 BNL D. Wallace, K. M. Johnson, K. Erickson pCO2, discrete LDEO T. Takahashi, A. Wilson Underway pCO2 SIO R. Weiss 14C PU R. Key, C. Thomas, R. Rotter ADCP, LADCP WHOI F. Bahr Halocarbons DU W. Groszko pALACE floats UW D. Swift Observer Venezuela Antonio Perez-Aguirre _______________ (1) CTD conductivity, temperature, and depth sensor; (2) CFC clorofluorocarbon; (3) ADCP acoustic Doppler current profiler; (4) LADCP lower ADCP; (5) ALACE autonomous Lagrangian circulation explorer. Participating institutions AOML Atlantic Oceanographical and Meterological Laboratory BNL Brookhaven National Laboratory LDEO Lamont-Doherty Earth Observatory UH University of Hawaii OSU Oregon State University PU Princeton University RSMAS Rosensteil School of Marine and Atmospheric Science, U. of Miami SIO Scripps Institution of Oceanography SIO/ODF Ocean Data Facility Scripps Institution of Oceanography UW University of Washington WHOI Woods Hole Oceanographic Institution DU Dalhousie University 2.3 Brief Cruise Summary For the section AR24 (cruise 147-2), the TCO2 and TALK systems were placed on board and set up on the R/V Knorr in Woods Hole, Massachusetts, during the period October 21-24, 1996, by the University of Miami TALK and the UH/BNL TCO2 measurement groups. The systems were successfully tested, and the Knorr departed Woods Hole on October 24, for the Azores with Mike McCartney as chief scientist. C. Winn was the CO2 group leader during the transit to the Azores and was present when one of the benches supporting one of the SOMMA- coulometer systems broke loose, threatening to destroy the analytical system. Fortunately, the analytical equipment suffered only minor damage, and the minor repairs required were completed by the time the ship was ready to begin the AR24 section. C. Winn left the ship in the Azores and was replaced by R.Rotter, A. Adams, and J. Tegeder, with R. Rotter serving as the group leader. The ship departed on the AR24 cruise from Ponta Delgada on November 1, 1996. The cruise track was, with minor deviations, basically a winter version of the two transoceanic A24 sections completed during the summer of 1997 (see Fig. 1). During the AR24 section, the principal problem with the TCO2 SOMMA systems Nos. 004 and 030 was the malfunctioning of the solenoid pinch valves used to dispense the sample. Some were damaged and ceased to work, while others were sensitive to power fluctuations and worked intermittently. Replacement valves were quickly consumed, souch that SOMMA system No.30 became the primary system. As a consequence, the bulk of the sample TCO2 analyses completed during the AR24 section (see Table 4 in Sect. 3.2) were made on system 030. These problems also resulted in the sampling of 10 fewer stations sampled for TCO2 than for TALK during the cruise, with most of the discrepancies occurring between November 14 and 20, 1996. After the concluding station 176 on December 2, 1996, the Knorr docked in South Hampton, United Kingdom, on December 3, 1996. Following the AR24 section, the analytical systems were repaired and re- calibrated. They were then set up on the R/V Knorr in Woods Hole, during the week of May 1319, 1997, by the University of Miami TALK and the BNL TCO2 measurement groups. Three SOMMA-coulometer systems and three TALK titrators were set up for the three WOCE sections (A24, A20, and A22). In addition to the discrete TCO2 systems (S/Ns 004 and 030), a third system (S/N 006) was set up for underway surface TCO2 measurements. The equilibrator-infrared (IR) gas analyzer system for the determination of partial pressure of CO2 (pCO2) in discrete sea water samples was set up by the scientists from LDEO. The discrete TCO2 systems were successfully calibrated using both CO2 calibration gas and the certified reference material (CRM) on May 17, 1997, while the calibration of the underway system (006) was completed on May 30. The Knorr departed Woods Hole on May 20 (Leg 151_1) with Dr. Tom Rossby as chief scientist. The TALK group remained onboard to test the instruments on the shake-down transit from Woods Hole to the embarkation point for Leg 151-2, Ponta Delgada on the island of St. Michael, Azores. Some 300 underway surface samples were drawn and analyzed for TALK during the shake-down cruise, but these data are not reported to the Carbon Dioxide Information Analysis Center (CDIAC). Greg Eischeid of WHOI completed the plumbing connections between the ships underway intake and the underway SOMMA (006). After correcting some minor problems, he obtained the required flow of 1 L/min through the underway system. Problems with operating the underway pipette were also encountered, but they were eliminated by software changes coordinated through BNL, so that by the time the ship arrived in Ponta Delgada, the underway system was operational. The most serious problem with the discrete TCO2 systems was that an erratic transmission reading with the system 030 coulometer madeking titrations impossible. This program was temporarily corrected by jiggling the voltage -to -frequency converter (VFC) and ensuring that all associated chips were properly seated. System 004 was tested successfully during the shake-down cruise, which ended on May 29, 1997, in Ponta Delgada. K. M. Johnson departed JFK Airport in New York on May 27, 1997, for Ponta Delgada via Lisbon and arriveding on May 28 in the Azores on May 28, where he joined L. Arlen, who was already in Ponta Delgada. The TALK and TCO2 measurement groups moved onboard ship on May 29, and readied the systems for the following day, when the ship departed Ponta Delgada on section A24 with Dr. Lynne Talley as chief scientist. Sample analysis began on system 004 immediately, but the system 030 coulometer once again exhibited unstable erratic transmission readings and was immediately replaced with the back-up unit. Sample analysis with this unit began on May 31, 1997. The cruise track for section A24 was basically rectangular, encompassing four separate sections (see Fig. 1) starting and ending in the Azores. The first section began at Terceira, Azores, proceeding northeastward towards the Goban Spur and crossing the Mediterranean Water/Labrador Sea Water mixing zone obliquely. Upon completion of the first section, the ship was diverted to Cork, Ireland, for an emergency exchange of crew members. The second section crossed the southern Rockall Trough, from Porcupine Bank to the southern end of the Rockall Bank. The third section crossed the northern part of the subpolar gyre, from the Hebrides to Rockall Bank, to Hatton Bank, to the Reykjanes Ridge and to Greenland near Angmassalik, crossing the Rockall Trough just north of the Anton Dohrn Seamount. Ice conditions at Greenland were favorable, and sampling was completed at stations well onto the shelf (average depth 500 meters). After a transit southward to Cape Farewell, Greenland, the fourth section began at Cape Farewell and proceeded southeastward to the Charlie Gibbs Fracture Zone, and then back to Terceira with the last Station on June 28, 1997. After a 6-day transit, the ship docked in Halifax, Nova Scotia, on July 5. The weather remained uniformly good throughout Leg A24, and all carbonate measurement systems were operated essentially without major problems. Perhaps the biggest disappointment was the failure to rendezvous with the nearby R/V Meteor in early June for a social gathering. Some 153 hydrographic stations were occupied during A24. TCO2 was measured on 92 of these stations and TALK was measured on 90. Therefore, roughly 60% of the stations occupied on this cruise were sampled for TALK and TCO2. This proportion was somewhat higher than the 50% of stations sampled on typical WOCE cruises due toas a result of an accelerated frequency of sampling. The increased frequency was brought about by making the A24 station interval dependent on bathymetry, which often varied radically over distances much less than the proscribed WOCE station interval of 30 nm. The carbon group sampled as many stations as possible given the limits imposed by the length of time required for the TCO2 and TALK determinations. In addition, discrete surface samples were taken at most stations, and the underway system was operated continuously on Section A24. Originally the A24 section was scheduled to terminate in St. Johns, but because repairs were required, the Knorr put into Halifax on July 4, 1997. An attempt was made to arrange for a back-up coulometer or to repair the damaged coulometer before the next cruise. Unfortunately, this did not work out, and scientists were still left without a back-up coulometer for the coming cruises. Because of the delay for repairs in Halifax, no direct handoff between CO2 measurement crews was made. The TCO2 relief team consisting of Rick Wilke and Ken Erickson arrived well after the first crew had left and just prior to the Knorr's departure on July 17, 1997, on section A20. However, Wilke had been briefed at BNL concerning the performance of the TCO2 systems and possible problems due to de-powering of the ship during the repairs. The relief crew for TALK consisted of Chris Sabine and Carrie Thomas, who were also responsible for the 14C samples. The Knorr left Halifax bound for Port of Spain, Trinidad, on July 17, 1997, with Dr. Robert Pickart as chief scientist and 31 other scientists. From July 17 until August 10, 1997, except for a couple of dog legs across the shelf regions, the Knorr occupied a series of stations in a straight line from the Newfoundland Shelf to the Suriname Shelf along approximately 52° W (WOCE Section A20). This Section is also a part of the ACCE and one of two North Atlantic WOCE meridional long-lines (the second long-line, A22, was visited during the subsequent cruise). In the early days of the cruise, heavy fog off of the Grand Banks made for slow going. Otherwise, the excellent weather experienced during the cruise allowed for the sampling of 95 hydrographic stations, which was more than planned. After the initial test station in 3000 m at 57° W, the ship steamed to the 1000-m isobath and the work commenced. During A20, the water masses sampled included the slopewaters, the Laborador Current, the Labrador Sea Water, the Deep Western Boundary Current, the Gulf Stream with a warm core ring, the Sargasso Sea, and finally, as the ship turned toward Trinidad, the North Brazil Current system. On the depths less than 1000 m, a 24-position conductivity, temperature, and depth (CTD) sensor was used, while for greater depths, a 36-position CTD was used. Hydographic station intervals ranged from 3 nm on the shelf, to 10-15 nm across the slopes, to 15-25 nm across the Gulf Steam, and 40 nm in the Sargasso Sea. Other physical oceanographic tasks completed included the deployment of 11 floats and drifters and the deployment or recovery of 4 moorings. The TCO2 systems 004 and 006 continued to operate well, but system 030 required the replacement of one pinch valve and a faulty isolation valve on July 19. Thereafter, this instrument functioned satisfactorily. The Knorr arrived in Port of Spain, Trinidad, on August 10, 1997. K. Johnson left New York on August 12 to relieve R. Wilke of the TCO2 measurement group, while K. Erickson and C. Thomas remained on board to continue the TCO2 and TALK measurements for the next section A22. The Knorr departed Port of Spain at 9 A.M. on August 15, and the first station was sampled only 12 hours out of port. Station 1 was a joint station with the R/V Hermano Gines from the EDIMAR Laboratory, Margarita, Venezuela, just outside the sill of the Cariaco Basin. Some joint nutrient samples were taken and analyzed aboard each ship. Then the Knorr began the Caribbean portion of the A22 transect, which ended with Station 23 on 300-m depth south of Puerto Rico on August 20, 1997. The Knorr jogged around the eastern end of the Island, and the transect was resumed north of Puerto Rico along approximately 66° W and continued until Station 77 in 200 m of water on the shelf south of Cape Cod, Massachusetts, on September 2, 1997. Some 77 WOCE hydrostations were occupied during the this leg. In addition, 10 floats and 9 drifters were deployed and one mooring was recovered. All of the carbon parameter instruments, including the underway SOMMA, functioned satisfactorily until the end of the cruise; and fortunately a back-up coulometer was never needed. The R/V Knorr docked in Woods Hole on September 3, where it was met by R. Wilke and E. Lewis from the BNL TCO2 group who helped pack the equipment, and the entire TCO2 measurement group with its equipment departed Woods Hole on the afternoon of September 4, 1997. 3. DESCRIPTION OF MEASUREMENTS AND METHODS 3.1 Hydrographic Measurements During the cruises, the responsibility for the hydrographic data was divided between Scripps Institution of Oceanography (SIO) (section A24) and WHOI (sections AR24, A20, and A22). Hence the hydrography description is given in separate sections for SIO and WHOI operations and methods. 3.1.1 SIO/Ocean Data Facility ODF Methods and Instrumentation (Section A24) The SIO hydrographical procedures are described in detail by Lynne Talley in the chief scientists cruise report for WOCE Section A24, which can be obtained on the WHPO web site at http://whpo.ucsd.edu/data/onetime/atlantic/a24/index.htm. Navigational data wereas logged automatically at 1-minute intervals on a Sun SPARC station. Underway bathymetry was acquired from the ships SeaBeam system at 5-minute intervals. These data were merged with the navigation data to provide a time-series of underway position, course, speed, and bathymetry, which were used for all station positions, depths, and for bathymetry on vertical sections. A thermosalinograph (Falmouth Scientific Instruments) was mounted on the bow approximately 3 m below the surface for underway salinity. The hydrographic casts were made with a 36-position 10-L rosette system belonging to the Ocean Data Facility (ODF) at SIO. This unit consisted of a 36-bottle frame, thirty-one 10-L Niskin bottles, an Neil Brown Instrument System (NBIS) Mark III CTD with dual conductivity and temperature sensors, transmissometer, LADCP, altimeter, and pinger. The rosette system was suspended from a three-conductor 0.322-inch electromechanical cable, and power to the CTD and pylon was provided through the cable from the ship. For the first 10 casts, a General Oceanics 1016 36-place pylon was used; thereafter a Sea Bird Electronics (SBE), 36-place pylon, and SBE 33 deck unit were used. The rosette was deployed from the starboard side hangar, and the port side Markey CTD winch was used throughout section A24. At the beginning of each station, the time, position, and bottom depth were logged,; the sensors were powered; and control was transferred to the CTD acquisition and control system in the ships laboratory and the CTD lowered to within 10 m of the bottom. The CTD provided real-time pressure, depth, temperature, salinity (conductivity), oxygen, and density, and these variables were used to select the sampling depths. At the end of each cast, water samples (full suite) were drawn in the following order: chlorofluorocarbons (CFCs), helium, oxygen, pCO2, TCO2, TALK, tritium, nutrients, and salinity. However, only salinity, oxygen, and nutrients were measured at every station. A log was kept to document the sampling sequence and to note anomalies (e.g., leaks, etc.), and WHP quality flags were assigned to each sample using the analyzed bottle salinities, oxygen, and nutrients. No major problems with the CTD operation were experienced, and the original set of 31 Niskin bottles was used throughout section A24. At the end of the cruise, the CTD and the entire acquisition and control system were packed and shipped back to SIO. The CTD was calibrated for pressure and temperature at the ODF calibration facility (La Jolla, CaliforniaA) in April 1997, prior to WOCE section A24. At sea, bottle salinity and oxygen were used to calibrate the conductivity and oxygen sensors, respectively, and the temperature calibration was checked with an SBE 35 laboratory-grade reference material. Further details concerning the pre- and post-cruise calibration of the CTD sensors can be found in the cruise report available from WHPO. ADCP and LADCP profiles were made throughout the section using the hull-mounted ADCP system permanently installed on the Knorr and the LADCP mounted vertically inside the rosette frame bottle rings. The quality of the shipboard ADCP to depths of 500 m was good throughout the cruise, as were the LADCP station profiles. Bottle salinity samples were collected after three rinses in 200-mL Kimax high alumina borosilicate bottles, sealed, and determined after thermal equilibration, usually within 8 to 12 hours of collection. Salinity was determined at 24°C on two Guildline Autosal Model 8400A salinometers located in a temperature-controlled laboratory (21.4 - 24.6°C). The salinometer was standardized with International Association for the Physical Sciences of the Ocean (IAPSO) standard seawater (SSW) batch P-127, using at least one fresh vial per cast. The accuracy of the determination was 0.002 relative to the SSW batch used. Salinity was then calculated for each sample (UNESCO, 1981) and merged into the data base. Bottle oxygen was determined by filling 125-mL iodine flasks to overflowing (3 x bottle volume) with a draw tube after two bottle rinses. Sample temperature was measured immediately with a thermometer imbedded in the draw tube. The Winkler reagents were added, the flasks stoppered, and shaken upon stoppering and shaken again 20 minutes later to ensure that the dissolved oxygen was completely fixed. Oxygen was determined according to the technique of Carpenter (1965), incorporating the modifications of Culberson et. al (1991) within 4 hours of collection on an SIO-designed automated oxygen titrator using photometric endpoint detection at an ultra-violet wave length of 365 nm. Standards prepared from pre-weighed potassium iodate were run each time the automated titrator was used, and reagent blanks were determined by analyzing distilled water. The final oxygen results have been converted to µmol/kg. Conversion was madedone using the in-situ temperature, not the temperature of the sample from the Niskin bottles, because of due to a software failure. Bottle volumes were precalibrated at SIO. The precision of the analysis calculated from 57 replicate pairs (duplicates drawn from the same Niskin bottle) was ± 0.004 mL/L. Phosphate, nitrate, nitrite, and silicate were determined on virtually every Niskin bottle closed from stations 1 through 153. The samples were collected in 45-mL high-density polypropylene, narrow-mouth, screw-capped centrifuge tubes whichthat were rinsed with HCL and then rinsed three times with sample before filling. The samples were analyzed on an ODF-modified four-channel Technicon AutoAnalyzer II, usually within 1 hour of the cast, in a temperature-controlled laboratory. If the samples were stored for longer than 1 hour prior to analysis, they were stored at 4°C (no more than 4 hours). The Auto Analyzer instrumentation which incorporates the method of Armstrong, Stearns, and Strickland et al. (1967) for silicate, the method of Armstrong et al. (1967) as modified for nitrate and nitrite, and the method of Bernhardt and Wilhelms (1967) for phosphate is described by Gordon and co- workers (Atlas et al., 1971; Hager et al., 1972; Gordon et al., 1992). Standards were analyzed at the beginning and end of each group of sample analyses with a set of secondary intermediate concentrations prepared by diluting pre-weighed primary standards. The primary standard for silicate was Na2SiF6; and for nitrate, nitrite, and phosphate, KNO3, NaNO2, and KH2PO4 were used, respectively. Chemical purities ranged from 99.97% (NaNO3) to 99.999% (KNO3). Deep seawater was also used as a substandard. Some 3439 nutrient samples were analyzed during section A24. 3.1.2 WHOI Methods and Instrumentation (Sections AR24, A20, and A22) Unless otherwise stated, procedures remain as in Section 3.1.1 above. The underway-Doppler speed log did not function during sampling of section A22, and the hull-mounted transducer had to be removed for repair. Otherwise, navigational and meteorological data wereas logged by the shipboard data acquisition system (dubbed Athena) at 1-minute intervals. These data include heading, time and date, geographic positioning system (GPS), wind speed and direction, sea surface temperature and conductivity, and additional meteorological data. A secondary suite of data calculated or derived from these data was also logged at 1-minute intervals. These files were also the source of event-specific data (e.g., station location). Underway salinity was calibrated with bottle salinity. For the WHOI sections, the Knorr was outfitted with equipment belonging to WHOI. For details see the chief scientists report for Sections A20 and A22 on the WHPO web site: http://whpo.ucsd.edu/data/onetime/atlantic/index.htm. The CTD used was a WHOI-modified NBIS Mark-III CTD with oxygen sensor, conductivity cell, LADCP, pressure transducer, temperature sensor, and pinger mounted on a 33-position 10-L Niskin bottle rosette frame. The AR24 section differed from the above A20 and A22 sections and virtually all other CO2 survey work because a 24-bottle rosette was used with 4-L sampling bottles, instead of the usual 10-L Niskin bottles, in order to reduce sampling time at the rosette when in late fall when seas were expected to be rougher. A General Oceanics-1016 pylon was used and was controlled using an SIO- furnished Surface Control Interface, a dedicated PC, and software provided by SIO/ODF. Temperature and pressure calibrations were performed at WHOI before section A20. The CTD was re-calibrated after its return to WHOI in December 1997. For details concerning the pre-cruise, at-sea, and post-cruise CTD calibrations, see the cruise report and Millard and Yang (1993). Oxygen, nutrients, and salts were analyzed from virtually every Niskin bottle closed during the cruise. Bottle salinity samples were collected after two rinses in 8-ounce glass bottles. Then they were thermally equilibrated to 22°C and analyzed on a Guildline Autosal Model 8400B salinometer. The salinometer was standardized once a day using IAPSO SSW Batch P-131 (dated October 10, 1996). The accuracy was ± 0.002. Bottle oxygen was determined by filling 15-mL brown glass tincture bottles. Oxygen was determined using a modified Winkler technique similar to that described by Strickland and Parsons (1972). The titration is automated using a PC controller and a Metrohm Model 665 Dosimat buret. The endpoint is determined amperometrically using a dual -plate platinum electrode, with a resolution of better than 0.001mL. The accuracy of the method is 0.02 mL/L with a standard deviation of replicate samples of ± 0.005. Standardization of the thiosulphate titrant was madedone daily. No problems were noted during the cruises. This technique is described further by Knapp, Stalcup, and Stanleyet al. (1990). The nutrient samples were collected in 30-mL high-density polypropylene bottles whichthat were loaded directly into the autosampler tray. The bottles were soaked in 10% HCl every other day, and rinsed three times with sample before filling. The samples were analyzed on the same SIO/ODF-modified four- channel Technicon AutoAnalyzer II used on A24, except that an Alpkem Model 303 autosampler was substituted for the ODF autosampler. The analytical methods are described in Gordon et al. (1994). 3.2. Total CO2 Measurements As on previous cruises, TCO2 was determined using automated dynamic headspace sample processors (SOMMA) with coulometric detection of the CO2 extracted from acidified samples. A description of the SOMMA-Coulometry System and its calibration can be found in Johnson et al., (1987), Johnson and Wallace, (1992), and Johnson et al., (1993). A schematic diagram of the SOMMA analytical sequence may be found in earlier cruise reports (see Johnson et al. 1995;,1996), and further details concerning the coulometric titration can be found in Huffman (1977) and Johnson, King, and Sieburth (1985). The methods used for discrete TCO2 on WOCE sections have been extensively dealt with in previous reports (Johnson et al., 1998a) and only need onlyto be briefly summarized. The AR24 section required modification of the usual sampling procedures. As noted in Section 3.1.2 above, 4-L sampling bottles were employed on the rosette, which limitinged the amount of sample available for the carbonate system analysts to one 500-mL bottle. Hence, the TCO2 coulometric titration analysis had to be completed before the partially empty 500-mL bottle was passed to the TALK group for the potentiometric alkalinity titration. There was enough sample to complete both measurements, but not enough time or sample for TCO2 replicate analyses from the same 500-mL sample bottle. The 4- L sampling bottles also made it impossible to draw duplicate samples from the same sampling bottle. Without duplicate samples from the hydrographic stations, standard measures of sample precision (DOE, 1994; Johnson, et al., 1998b) could not be completed on the AR24 section. Samples were poisoned with 100 µL of a 50% solution of HgCl2, and analyzed for TCO2 within 24 hours of collection (DOE, 1994). For sections A24, A20, A224, single or duplicate samples were collected in 300-mL biological oxygen demand (BOD) bottles, poisoned with 100 µL of a 50% solution of HgCl2, and analyzed for TCO2 within 24 hours of collection, according to standard operating procedures (DOE, 1994). The samples were stored in a dark refrigerator at 46°C until approximately 12 hours before analysis, when they were removed and placed in a temperature bath at 18-20°C and thermally equilibrated. The SOMMA sample pipette and sample bath were also kept at approximately 20°C. Duplicate samples were usually collected on each cast at the surface and from the bottom waters. For some casts, three sets of duplicates were taken. The duplicates were analyzed within the run of cast samples from which they originated souch that the time elapsed between duplicate analyses was 3-12 hours. As per standard operating procedure (DOE 1994), Certified Reference Material (CRM) was routinely analyzed according to DOE (1994) guidelines. The CRM was supplied by Dr. Andrew Dickson of the SIO, and for the North Atlantic cruises, batches 33, 36, and 37 were used. The certified values for these batches were: TCO2 = 2009.85 µmol/kg @ salinity = 33.781 for batch 33; TCO2 = 2050.21 µmol/kg @ salinity = 35.368 for batch 36; and TCO2 = 2044.15 µmol/kg @ salinity = 34.983 for batch 37. The CRM TCO2 concentration was determined by vacuum-extraction/manometry in the laboratory of C. D. Keeling at SIO. An accurately known volume of seawater was injected from an automated to- deliver (TD) pipette into a stripping chamber. Following acidification, the resultant CO2 from continuous gas extraction was dried, and coulometrically titrated on a model 5011 UIC Ccoulometer with a maximum titration current of 50 mA in the counts mode (the number of pulses or counts generated by the coulometers VFC during the titration was displayed). In the coulometer cell, the acid (hydroxyethylcarbamic acid) formed from the reaction of CO2 and ethanolamine is titrated coulometrically (electrolytic generation of OH-) with photometric endpoint detection. The product of the time and the current passed through the cell during the titration (charge in coulombs) is related by Faradays constant to the number of moles of OH- generated and thus to the moles of CO2 whichthat reacted with ethanolamine to form the acid. The age of each titration cell is logged from its birth (time that electrical current is applied to the cell) until its death (time when the current is turned off). The age is measured in minutes from birth (chronological age) and in mgC titrated since birth (carbon age). Each system was controlled with an IBM -compatible PC equipped with two RS232 serial ports (coulometer and barometer), a 24-line digital input/output card (solid state relays and valves), and an analog -to -digital (A/D) card (temperature, conductivity, and pressure sensors). Real Time Devices (located in State College, PA 16803) manufactured the cards. The SOMMA temperature sensors (model LM34CH, National Semiconductor, Santa Clara, CA) with a voltage output of 10 mV/F were calibrated against thermistors certified to 0.02°F prior to the cruise using a certified mercury thermometer. These sensors monitored the temperature of SOMMA components, including the pipette, gas sample loops, and the coulometer cell. The SOMMA software was written in GWBASIC Version 3.20 (Microsoft Corp., Redmond, WA), and the instruments were driven from an options menu appearing on the PC monitor. With the coulometers operated in the counts mode, conversions and calculations were made using the SOMMA software rather than the programs and the constants hardwired into the coulometer circuitry. The SOMMA-coulometry systems were calibrated with pure CO2 (calibration gas) using hardware consisting of an 8-port gas sampling valve (GSV) with two sample loops of known volume [determined gravimetrically by the method of Wilke, Wallace, and Johnson et al., (1993)] connected to the calibration gas through an isolation valve; with the vent side of the GSV was plumbed to a barometer. When a gas loop was filled with CO2 at known temperature and pressure, the mass (moles) of CO2 contained therein was calculated, and the ratio of the calculated mass to that determined coulometrically iwas the calibration factor (CALFAC); the CALFAC which was used to correct the subsequent sample titrations for small departures from 100% recoveries (DOE, 1994). The standard operating procedure was to make gas calibrations daily for each newly prepared titration cell ([normally, one cell per day and three sequential calibrations per cell at a carbon age of 39 mgC (mean age @ 6 mgC), with the result of the third calibration taken as the CALFAC if it was consistent with the second, (i.e., agreement to ± 0.1% or better)]. Daily gas calibrations were made on both systems throughout the cruises. The "to-deliver" volume (Vcal) of the sample pipettes was determined (calibrated) gravimetrically prior to the cruise to ± 0.02% or better in October of 1996. The calibration was checked periodically during all cruises by collecting aliquots of deionized water dispensed from the pipette into pre-weighed serum bottles. The serum bottles were crimp-sealed and weighed immediately during the on-shore laboratory calibrations, or returned to shore where they were reweighed on a model R300S balance (Sartorius, Gttingen, Germany) balance as soon as possible. The apparent weight (g) of water collected (Wair) was corrected to the mass in vacuum (Mvac) with the to- deliver volume being Mvac divided by the density of the calibration fluid at the calibration temperature. After the AR24 section in 1996, the system pipettes were dismounted and replaced with chemically cleaned pipettes in March, 1997. For the 1997 sections, the calibration volumes (Vcal) at the calibration temperature (tcal) of the sample pipettes were redetermined to ± 0.01% from a set of calibration samples taken on July 3, 1997, on aboard the Knorr at the completion of section A24 and were weighed on September 17. The TCO2 pipette volumes for the four North Atlantic sections are summarized in Table 2. Table 2: The "to-deliver" pipette volume (Vcal) and calibration temperature (tcal) for the discrete SOMMA-Coulometer Systems (S/N 004 and 030) used on WOCE Section AR24 (1996) and Sections A24, A20, and A22 (1997) ______________________________________________________ Section System S/N Vcal (mL) tcal (C) ------------------- ---------- --------- -------- AR24 (1996) 004 21.8927 19.91 A24/A20/A22 (1997) 004 21.2630 19.19 AR24 (1996) 030 21.3733 20.91 A24/A20/A22 (1997) 030 25.8544 19.52 ______________________________________________________ The sample volume (Vt) at the pipette temperature was calculated from the expression: Vt = Vcal [1 + av (t - tcal)] where av is the coefficient of volumetric expansion for pyrex-type glass (1 X 10^-5/°C), and t is the temperature of the pipette at the time of a measurement. The mean pipette temperature on the AR24 section in 1996 was 20.32 ± 0.51°C (n = 948), and on the 1997 North Atlantic Sections it was 19.55 ± 0.52°C (n = 4666). The factory-calibrated coulometers were electronically calibrated independently in the laboratory before the cruise as described in Johnson et al. (1993, 1996) and DOE (1994), and the terms INTec and SLOPEec were obtained and entered into the software for each system. The micromoles of carbon titrated (M), whether extracted from water samples or the gas loops, was: M = [Counts/4824.45-(Blank X Tt )-(INTec X Ti)]/SLOPEec where 4824.45 (counts/µmol) is a scaling factor obtained from the factory calibration; Tt wais the length of the titration in minutes; Blank is the system blank in µmol/min; INTec is the intercept from electronic calibration in µmol/min; Ti is the time in minutes during the titration where current flow was continuous; and SLOPEec is the slope from electronic calibration. Note that the slope obtained from the electronic calibration procedure applied for the entire length of the titration, but the intercept correction applied only for the period of continuous current flow (usually 34 min) because the intercept can only be calculated only from calibrated levels of current flowing continuously. Unfortunately, the coulometer system 030, which was electronically calibrated prior to the AR24 cruise and again in March 1997, had to be replaced at the start of section A24 in May 1997. However, the replacement coulometer (S/N CBE-9010-V) was calibrated at the factory on March 20, 1997. Hence we assumed that the replacement coulometer was properly calibrated, and we entered the default calibration coefficients into the software (SLOPEec = 1.0 and INTec = 0.0). The system 004 was also recalibrated in March 1997 following the AR24 cruise with nearly identical results to those obtained in October 1996, and it was not recalibrated during the 1997 WOCE sections. The electronic calibration coefficients, along with the mean gas calibration factors determined for the North Atlantic section discrete TCO2 coulometers, are given in Table 3. Table 3 illustrates an advantage of the independent laboratory electronic calibration procedure. The mean CALFAC for systems 004 and 030 using the laboratory-determined electronic calibration coefficients was approximately 1.0036 (or 99.64% recovery of the theoretical mass of CO2 calibration gas measured coulometrically) vs 1.0053 (99.47% recovery) for the factory- calibrated coulometer. Hence, a small percentage (0.17%) of the less than 100% recovery for known masses of CO2 coulometrically titrated can be explained by a factory-calibration procedure whichthat is apparently slightly less accurate than the laboratory calibration. This difference has been consistent throughout the CO2 survey. Table 3: The electronic calibration and the mean gas calibration coefficients for the discrete TCO2 systems on WOCE Section AR24 (1996) and Sections A24, A20, and A22 (1997) __________________________________________________________________________ Section System SLOPE INT(ec) CALFAC(n) St. dev. Rel. st. S/N (ec) µmol/min dev. (%) ----------- ------ -------- -------- ------------ -------- -------- AR24 004 0.999372 0.002528 1.003892(9) 0.000650 0.06 A20/A22/A24 004 0.998905 0.001466 1.003361(63) 0.000740 0.07 AR24 030 0.999306 0.003550 1.003780(26) 0.000497 0.05 A20/A22/A24 030* 1.000000 0.000000 1.005344(59) 0.001369 0.13 ------------------------------------------------------------------------ *Factory-calibrated coulometer installed at the beginning of the A24 section in May 1997. __________________________________________________________________________ For water samples, the discrete TCO2 concentration in µmol/kg was calculated from: TCO2 = M X CALFAC X [1/(Vt X P)] X dHg where P is the density of sea water in g/mL at the measurement temperature and sample salinity calculated from the equation of state given by Millero and Poisson (1981), and dHg is the correction for sample dilution with bichloride solution (for the AR24 section in 1996 dHg = 1.0002 and for the 1997 sections dHg = 1.000333). One of the SOMMA-Coulometry Systems (S/N 004) was equipped with a conductance cell (Model SBE-4, Sea-Bird Electronics, Inc., Bellevue, WA) for the determination of salinity measurement as described by Johnson et al. (1993). Whenever possible SOMMA and CTD salinity were compared to identify mistrips or other anomalies, but the bottle salinity (furnished by the chief scientist) was used to calculate TCO2. Quality control-quality assurance (QC-QA) was assessed from the results of the 275 CRM analyses made using systems 004 and 030 during the four North Atlantic sections. These data are summarized in Table 4, and the temporal distribution of the differences is plotted in Fig. 2 for section AR24 (1996) and in Fig. 3 for sections A24, A20, and A24 (1997). Table 4: The mean analytical difference (∆TCO2 = measured - certified) and the standard deviation of the differences between measured and certified TCO2 on WOCE Sections AR24, A24, A20, and A22 _______________________________________________ Section System ∆TCO2 St. dev. n S/N (µmol/kg) (µmol/kg) ---------- ------ --------- --------- --- AR24 004 1.42 2.10 16 AR24 030 1.54 1.88 49 Mean/total 1.51 1.92 65 A24 004 0.04 1.10 49 A20 004 0.23 1.20 42 A22 004 0.06 0.69 17 Mean/total 0.10 1.08 108 A24 030 0.79 1.00 48 A20 030 0.44 1.43 35 A22 030 0.26 1.22 19 Mean/total 0.57 1.21 102 Overall mean/total 0.61 1.47 275 _______________________________________________ The overall accuracy of the CRM analyses was better than 1 µmol/kg on both systems for the four North Atlantic sections, with a combined overall mean difference of + 0.61 µmol/kg (n = 275). However, Table 4 shows that on the AR24 section (1996), the mean difference and the standard deviation of the differences were noticeably larger for both systems compared towith the 1997 sections (A24/A20/A22). This may be due in part to mechanical problems experienced by the AR24 measurement group, operator procedures, and possibly the relatively short time available to service and re-calibrate the systems prior to the AR24 section. The latter was brought about by the fact that the system 004 had been used in the Indian Ocean from 1994-1996, and was only returned to BNL for service, repair, and re-calibration in the fall of 1996. System 030, which was a newly built system returned to the laboratory after a test cruise in the North Atlantic, also was not returned until the summer of 1996. For the 1997 sections, both systems were available in the laboratory for servicing from January through May of 1997. Indeed, the 1997 WOCE sections represented the only opportunity during the CO2 survey for the BNL measurement group to thoroughly service and test the systems, reagents, and analytical gases in the laboratory with real samples and CRM prior to shipment. As a result, the accuracy and precision of the CRM analyses made in 1997 (see Table 4) probably represents the highest quality possible for these systems under field conditions. All CRM analyses made on the discrete systems (004 and 030) during the 1997 sections are reported in Table 4. However, for section AR24, two CRM analyses were classified as outliers and dropped from the data set. These were CRM No. 206 run on system 030 on November 23 (difference = + 10.17 µmol/kg) at a cell carbon age of 39.5 mgC, and CRM No. 600 on system 030 on November 28 (difference = + 7.99 µmol/kg) at a carbon age of 35.7 mgC. One CRM analysis (CRM No. 352) run on system 004 on December 1 is not included in the data set because the titration did not attain an endpoint. The second phase of the QC-QA procedure was an assessment of precision. As described in the text, duplicate samples could not be taken during the AR24 section in 1996. Hence the only estimate of AR24 sample precision was the standard deviation of the differences between the measured and certified TCO2 on both systems (see Table 4). Because differences from both systems have been combined, the CRM measurements are analogous to the sample duplicates analyzed on each system and should reflect both random and systemic error (bias). The decrease in precision for the CRM analyzed on the AR24 section in 1996 (± 1.92 µmol/kg) compared towith the CRM analyzed in 1997 (± 1.20 µmol/kg) was consistent with the problems described for the 1996 leg. The good agreement in TCO2 between systems in 1996 (see Table 4) suggests that the analyzingsis of duplicate seawater samples on each system, as was the casedone in 1997, might have yielded a higher precision than the precision of the CRM differences. Nevertheless, without sample duplicates, the AR24 sample precision must be based on the CRM analyses. Hence the precision of the TCO2 determination for the AR24 section in 1996 was ± 1.92 µmol/kg (n = 65). Because procedures and performance varied from 1996 to 1997, separate estimates of sample precision were required for each year; and the data for 1997 are given in Table 5. By 1997 the deployment of two independent SOMMA systems side-by-side was routine, and the conventions employed for the estimation of precision in the earlier WOCE data reports are retained in Table 5. For sections A24, A20, and A22 in 1997, the single-system precision was determined from samples with duplicates analyzed on the same system (either 004 or 030). The sample precision was calculated using duplicates that were analyzed on both systems (004 and 030). Table 5: Precision of the discrete TCO2 analyses on WOCE Sections A24, A20, and A22 ___________________________________________________________________ Section | Mean absolute difference | Pooled standard deviation |--------------------------|-----------|----------------- | σbs | ± St. | K | Sp^2 | K | n | d.f. | (µmol/kg) | dev. | | (µmol/kg) | | | --------|-------------------------------------------------------- | Single-system precision --------|-------------------------------------------------------- A24 | 1.08 | 1.01 | 175 | 1.04 | 175 | 350 | 175 A20 | 0.95 | 1.14 | 84 | 1.04 | 84 | 168 | 84 A22 | 0.99 | 0.93 | 71 | 0.96 | 71 | 142 | 71 --------|-------------------------------------------------------- | Sample precision --------|-------------------------------------------------------- All | 1.76 | 1.41 | 56 | 1.59 | 61 | 122 | 61 ___________________________________________________________________ Single-system and sample precision have been separately assessed in Table 5 as: • "between-sample" precision (σbs), which is the mean absolute difference between duplicates (n=2) drawn from the same Niskin bottle; and • the pooled standard deviation (Sp^2) calculated according to Youden (1951), where K was the number of samples with duplicates analyzed, n was the total number of replicates analyzed from K samples, and n - K was the degrees of freedom (d.f.). Single-system precision provided a measure of drift in system response during a sequence of sample analyses. This is because the time elapsed between duplicate analyses on the same system using the same coulometer cell was deliberately kept at from 3 to 12 hours on the assumption that drift or change in response would be reflected in the single-system precision by an increase in the imprecision of the duplicate analyses. Sample precision, on the other hand, was measured because TCO2 measurements were made on two separate systems and an estimate of overall sample precision for the section (s), independent of which analytical system was used, was required. Sample precision is the most conservative estimate of precision, incorporating several sources of random or systematic (bias) error. As on other sections in the Atlantic Ocean (e.g., A8 and A10) where SOMMA- Ccoulometer systems have been run in parallel, the sample precision was slightly less precise than the single-system precision. This indicated that changes in system response during the coulometer cell lifetime in 1997 were clearly within the precision of the method (± 1.59 µmol/kg), while the slight but consistent decrease in sample precision compared towith single-system precision was probably due at least in part to a small bias between the 004 and 030 systems. Although the precision was equivalent for both systems, system 030 gave on average slightly higher results than system 004. For example, the mean ∆TCO2 for system 004 CRM was +0.10 µmol/kg, but it was +0.57 µmol/kg for system 030 CRM (see Table 4); while the mean of the seawater samples (n = 56, Table 5) analyzed on 030 was +1.17 µmol/kg higher than the mean for the same samples analyzed on system 004. Hence the uniformly excellent single-system precisions for 1997 can not be used for sample precision, and analyzing duplicate replicates on each system remains the definitive measure of the overall precision of the 1997 data set and the TCO2 calibration procedures. The two discrete systems should give the same result for the same sample, and the extent to which they differ is a measure of the overall precision of the data set obtained with two independent systems. For TCO2 on the 1997 North Atlantic WOCE sections, the precision of the TCO2 determination was ± 1.59 µmol/kg (K= 56). The North Atlantic sample precision for all four sections in 1996 and 1997 (± 1.92 and ± 1.59 µmol/kg, respectively) is in good agreement with the published and unpublished sample precision for other WOCE sections where systems were run in parallel: AE1, 1991 (± 1.65 µmol/kg); P6, 1992 (± 1.65 µmol/kg); A10, 1993 (± 1.92 µmol/kg); A8, 1994 (± 1.17 µmol/kg); Indian Ocean, 1995 (± 1.20 µmol/kg). During the 1997 North Atlantic sections, a limited number of duplicate samples (K = 6) were analyzed from two different Niskin bottles closed at the same depth, and the mean absolute difference and standard deviation was 0.77 ± 0.50 µmol/kg, which was consistent with earlier findings (e.g., Johnson et al., 1998a,; Johnson et al. 2001) that there were likely no significant analytical effects due to gas exchange with the overlying headspace of the Niskin bottles during sampling. Tables 4 and 5 show an internally consistent data set of high quality with excellent accuracy (< or = 2.0 µmol/kg), high single-system precision (< or = ± 1.0 µmol/kg), and a slightly higher imprecision for the sample precisions (± 1.59 - 1.92 µmol/kg). Based on these data, the TCO2 data clearly meet survey criteriaon for accuracy (< or = 4.0 µmol/kg) and precision, and as with previous data submissions, no correction for instrumental bias or CRM analytical differences has been applied to the TCO2 data. 3.3. Total Alkalinity Measurements TALK and pH, were measured using an automated potentiometric titration system developed at the University of Miami (hereafter designated as MATS). The MATS is described by Millero et al. (1993a). It consisted of two parts: a Metrohm model 665 Dosimat titrator and a pH meter (Orion, Model 720A) which are interfaced with a PC. A water-jacketed, fixed -volume (~200 mL), closed Plexiglass sample cell, of greater volume than but otherwise similar to those used by Bradshaw and Brewer (1988), was used to increase the precision of the measurements. The cell, titrant burette, and sample cell were theromstatted at 25 ± 0.05°C using a constant temperature bath (Neslab, Model RTE 221). A Lab Windows/CVI program was used to run the titrators, record the volume of titrant added, and to record the measured electromagnetic frequency (emf) of the electrodes through RS232 serial interfaces. The electrodes for measuring the emf during the titration consisted of a ROSS glass pH electrode (Orion, Model 810100) and a double-junction Ag/AgCl reference electrode (Orion, Model 900200). Seawater samples were titrated by adding enough HCl to exceed the carbonic acid end point of the titration. During a typical titration, the electro- magnetic frequency (emf) readings were recorded until stable (± 0.05 mV). Normally, at this point, a fixed volume of acid would be added,; however, the MATS were designed to add enough acid to increase the voltage by a pre- assigned increment (13 mV). This was done to give an even distribution of data points over the course of a full titration, which consists of 25 data points and takes about 20 minutes. With two systems, approximately 7 hours was required to run a 31-bottle station cast. As noted in Sections 3.1 and 3.2 above, a 4-L Niskin sampling bottles were employed on the rosette, which limited the amount of sample available for the carbonate system analysts to one 500-mL bottle. Hence there was not enough sample to complete duplicate alkalinity analyses from the same bottle or to draw duplicate samples from the same sampling bottle. The titrant (acid) used throughout the cruises was prepared, standardized, and stored in 500-mL borosilicate glass bottles for use in the field. A single 55- gallon batch of 0.25-m HCl acid was prepared by dilution of concentrated HCl (AR Select Mallinckrodt). The acid was prepared in 0.45 m NaCl to yield a total ionic strength similar to that of seawater salinity 35.0 (I = ~ 0.7 M). The acid was standardized by coulometry (Taylor and Smith, 1959; Marinenko and Taylor, 1968). The acid molality was also checked by titration on seawaters with known alkalinities, and sub samples were sent to the laboratory of A. Dickson at SIO for an independent laboratory determination of the molality. The calibrated molality of the acid used for the North Atlantic WOCE Sections was 0.24892 ± 0.00003 m HCl. The consistency of the method was checked for each cast using low -nutrient surface seawater, and the accuracy of the method was checked by analyzing CRM Batches 33 (1996), 36, and 37 (1997) and comparing the analyzed values with the certified TALK in the same manoner as for TCO2 (see also Section 3.2 for batch data). The mean differences between at-sea measurements and the certified TALK values are given in Table 6. The TALK of each batch was also determined in the laboratory by weight titrations, which were found to agree with the certified values to ± 2 µmol/kg. In addition, the pH of the CRM batches was also determined in the laboratory spectrophotometrically according to the methods of Clayton and Byrne (1993) prior to the cruise. The at-sea titration pH measurements were also compared towith the pre-cruise spectrophotometric values, and and the reader is referred to Millero et al. (1999) for further details. Table 6: The mean analytical difference between analyzed and certified TALK for the MATS on WOCE Section AR24 (1996), and Sections A24, A20, and A22 (1997) __________________________________________________________ CRM TALK Measured TALK ∆TALK Section Cells n µmol/kg µmol/kg µmol/kg ------ --------- --- -------- ------------- ------- AR24 2, 19, 17 59 2234.9 2233.3 -1.6 A24 2, 18, 12 148 2283.9 2283.3 -0.6 A20 2, 18, 12 96 2314.1 2217.1 3.0 A22 2, 12 65 2314.1 2215.4 1.3 __________________________________________________________ The mean differences between the at -sea measurements and the certified TALK were within 3.0µmol/kg (Table 6). Hence the measured and certified TALK were in good agreement. For pH and TCO2, the corresponding results were 0.021 and 9 µmol/kg, respectively, with the larger deviation in pH attributable to the non-Nernstian behavior of the electrodes near a pH of 8 (Millero et al., 1993b). The at -sea sample alkalinity titrations were corrected using the results for the CRM. For TALK, the CALFAC used to correct the at sea measurements was: CALFAC = CRM (certified value)/(at- sea value), and for pH the CALFAC was: pH = pH (CRM)/pH (at-sea). Duplicate samples were usually taken for each station in the same manner as for TCO2 (surface and deep) and analyzed to determine and monitor the precision of the MATS. The average difference between replicates was ± 1.0, ±1.1, and ± 1.1 µmol/kg for sections A24, A20, and A22, respectively, which demonstrated the high precision of the MATS throughout the study. A preliminary description of the major trends in the data and the behavior of alkalinity over time in the North Atlantic is given by Millero et al. (1999). 3.4. Discrete pCO2 Measurements The discrete measurements of pCO2 were performed by the LDEO group on three of four sections of the North Atlantic survey. During the WOCE sections A24, A20, and A22, a total of 2,465 samples were analyzed onboard the R/V Knorr (1,103, 595, and 767 samples respectively). On the earlier WOCE section AR24, discrete pCO2 was not measured. An automated equilibrator-infrared (IR) gas analyzer system was used during the expedition for the determination of partial pressure of CO2 in the seawater samples. Its design is similar to that described by Chipman et al., Marra, and Takahashi (1993) with the exception that the gas chromatograph was replaced with an infraredIR gas analyzer. The equilibrator-IR system is shown schematically in Fig. 4. The system consists of a circulation pump plumbed to re-circulate air in a closed system through porous plastic gas dispersers immersed in a 250 -mL seawater sample. The seawater sample is contained in a 250-mL Pyrex reagent bottle with a standard taper-ground glass stopper whichthat serves as an equilibration vessel. A Pyrex extension tube (~ 20 mL), thatwhich has a standard taper-ground glass male-joint to form an air-tight seal with the reagent bottle, is connected to the mouth of the reagent bottle to provide an extra headspace forto preventing seawater from entering the gas circulation line. Four sets of flasks and circulation pumps are used so that four water samples can be processed concurrently. Because the partial pressure of CO2 is sensitive to temperature, the equilibration flasks are kept immersed in a water bath maintained at 20°C. The temperature at which the water sample is equilibrated with circulating gas is measured with a precision of ± 0.01°C and is recorded. An electrically driven Valco 10-port valve (the equilibrator selection valve in Fig. 4) is used to isolate each of the equilibrators during the initial equilibration. Manually operated 2-way and 3-way Whitey valves allow the headspace in each equilibrator to be filled with a calibration gas of known CO2 concentration, creating a known initial condition for the headspace (about 40 mL) before equilibration. The equilibrator is open to the laboratory air through isolation coils attached to the low-pressure side of the equilibrator, keeping the total pressure of equilibration the same as the ambient atmospheric pressure. The atmospheric pressure is measured with a high- precision electronic barometer with an accuracy of better than 0.05%, and is recorded. It takes about 20 minutes for each water sample to be thermally equilibrated with the constant-temperature water bath, and the headspace gas is re-circulated through the water sample throughout the period to iensure CO2 equilibration. An electrically driven Valco 6-port valve (the sample selection valve in Fig. 4) is connected to the equilibrator election valve and to the calibration gas selection valve. This allows toselection of the gas sample to be analyzed for CO2: the equilibrated sample gas or one of the four calibration gases. A 2-way normally-closed Skinner solenoid valve on the output of the calibration gas selection valve controls the flow of the calibration gases to the sample selection valve. It also providesd a necessary second means of stopping the flow of the calibration gases to prevent their accidental loss in case of a control malfunction. The concentration of CO2 in the gas equilibrated with the seawater sample is determined using IR gas analyzer (LICOR Model 6125) in a flow-through mode. A 0.5-mL aliquot of equilibrated headspace gas, representing less than 1% of the circulating gas, is isolated using a gas pipette (attached to the sampling valve in Fig. 4), and swept with CO2-free air (or pure nitrogen gas) flowing at a constant rate of about 50 mL/min. For low-pCO2 samples, a 1-mL gas pipette (attached to the sampling valve) is used. The sample gas is passed through a permeation drying tube for the removal of water vapor, and injected into the infraredIR gas analyzer cell (about 7 mL in volume) filled previously with CO2-free air. The displaced CO2-free air is discharged out of the cell into the laboratory. The small volume of the gas sample iensures that all of the CO2 from the gas pipette areis found in the analyzer cell at the same time, so that the peak height is proportional to the amount of CO2 present in the gas pipette. Drying of the sample gas avoids the effects of pressure-broadening of the CO2 absorption spectra and of dilution caused by water vapor. The amount of CO2 in the sampling pipette is a function of the loop volume, temperature, and pressure. The temperature is held constant and measured, and the pressure of the sample gas is same as the barometric pressure, which is measured with an accuracy of better than 0.05%. The peak height, which represents the number of moles of CO2 in the sample gas, is calibrated every 1.5 hours using a quadratic equation fitted to three calibration gas mixtures (366.52, 788.8 and 1211.4 ppm mole fraction in dry air). The analytical procedure begins with water samples being drawn from the 10-L Niskin bottles off a rosette directly into 250-mL Pyrex reagent bottles. These served as both sample containers and equilibration vessels. The samples were immediately inoculated with 100 µL of 50% saturated mercuric chloride solution, sealed airtight with ground glass stoppers to prevent biological modification of the pCO2, and stored in the dark until analysis. Measurements were normally performed within 24 hours of sampling. A headspace of 3 to 5 mL was left above the water to allow for thermal expansion during storage. Prior to analysis, the sample flasks were brought to the water bath temperature of 20°C in the constant -temperature bath. The equilibrator headspace, including the extension tube and the gas circulation tubings, wasere filled with a calibration gas of known CO2 concentration. The gas in the equilibrators, and in the tubing that connects them to the gas pipette loop, was re circulated continuously for about 20 minutes through a gas disperser immersed in the water. This provided a large surface area for gas exchange between the sample water and circulating gas, and equilibrium for CO2 was attained in 15 minutes. The temperature of the bath water was assumed to be that forf the sample water, and was measured at the time of equilibration with a precision of ±0.01°C using a thermometer calibrated against a NIST-certified thermometer. This temperature is reported in the data tables as TEMP_PCO2 and showed no variation at a limit of ±0.01°C. The equilibrated air samples awere saturated with water vapor at the temperature of equilibration and had the same pCO2 as the water. By injecting the air aliquot into the infraredIR analyzer after the water vapor iswas removed, the concentration of CO2 was measured. Therefore, the effect of water vapor must be taken into consideration for computing pCO2 as follows: pCO2 (µatm) = [Cmeas (ppm)] X [total press. of equilibration (atm) - water vapor press. (atm)] where Cmeas is the mole fraction concentration of CO2 in dried equilibrated air. The total pressure of equilibrated air is measured by having the headspace in the equilibrator flask always at atmospheric pressure. The latter was measured with an electronic barometer at the time each equilibrated air sample iwas injected into the IR analyzer for CO2 determination. The water vapor pressure was computed at the equilibration temperature, and salinity of the seawater. Cmeas was determined by using a quadratic equation fit to three of the calibration gas mixtures. The concentrations for standard gases used are traceable to the WMO reference scale through analysis in the laboratories of C. D. Keeling of SIO (La Jolla, California) and of Pieter P. Tans of NOAA/CMDL (Boulder, Colorado). The values of the standard gas mixtures used during this cruise were: 366.52 ppm CO2, 788.0 ppm CO2, and 1211.4 ppm CO2. Corrections were made to account for the change in pCO2 of the sample water due to the transfer of CO2 between the water and circulating air during equilibration. We know the pCO2 in equilibrated, perturbed water and the TCO2 by coulometry before the equilibration. We can also calculate the change in TCO2 in the water based on the change in pCO2 between the post-equilibrium value and the known concentration in the pre-equilibrium condition. With the pre-equilibrium TCO2 plus the perturbation in TCO2 during equilibration, the post-equilibrium TCO2 value was obtained. Using the post-equilibrium TCO2 and measured pCO2 values, TALK at the end of the equilibration was calculated, knowingbased ousing the temperature, salinity, phosphate, and silicate data. Since the perturbation does NOT change the TALK, the pre-equilibrium pCO2 from the pre-equilibrium TCO2 was calculated, the calculated TALK, and the temperature, salinity, etc., were calculated. This is the value that was reported as pCO2, the pre-equilibrium calculated value. The magnitude of this correction is generally less than 2 µatm. Details of the computational scheme are presented in a DOE technical report by Takahashi, et al. (1998). The pCO2 values reported in this data set are expressed as micro-atmospheres at the temperature of equilibration. The precision of the pCO2 measurement for a single hydrographic station was estimated to be about ±0.15% based on the reproducibility of replicate equilibrations. The station-to-station reproducibility was estimated to be about ±0.5%. 4. DATA CHECKS AND PROCESSING PERFORMED BY CDIAC An important part of the numeric data packaging process at the Carbon Dioxide Information Analysis Center (CDIAC) involves the quality assurance (QA) of data before distribution. Data received at CDIAC are rarely in a condition that would permit immediate distribution, regardless of the source. To guarantee data of the highest possible quality, CDIAC conducts extensive QA reviews that involve examining the data for completeness, reasonableness, and accuracy. The QA process is a critical component in the value-added concept of supplying accurate, usable data for researchers. The following information summarizes the data processing and QA checks performed by CDIAC on the data obtained during the R/V Knorr cruise along WOCE Sections AR24, A24, A20, and A22 in the North Atlantic Ocean. • The final carbon-related data were provided to CDIAC by the ocean carbon measurement PIprincipal investigators listed in Section 2. The final hydrographic and chemical measurements and the station information files were provided by the WOCE Hydrographic Program Office (WHPO) after quality evaluation. A FORTRAN 90 retrieval code was written and used to merge and reformat all data files. • Every measured parameter for each station was plotted vs depth (pressure) to identify questionable data points using the Ocean Data View (ODV) software (Schlitzer 2001) Station Mode (Fig. 5). • Section plots for every parameter were generated using ODVs Section Mode in order to map a general distribution of each property along all North Atlantic Ocean sections (Fig. 6). • To identify noisy data and possible systematic, methodological errors, property-property plots were generated (Fig. 7) for all parameters, carefully examined, and compared with plots from previous expeditions in the North Atlantic. • All variables were checked for values exceeding physical limits, such as sampling depth values that are greater than the given bottom depths. • Dates, times, and coordinates were checked for bogus values (e.g., values of MONTH < 1 or > 12; DAY < 1 or > 31; YEAR < 1996 or > 1997; TIME < 0000 or > 2400; LATITUDE < 7.000 or > 67.000; LONGITUDE < -68.000 or > -8.000. • Station locations (latitudes and longitudes) and sampling times were examined for consistency with map and cruise information supplied by PIprincipal investigators. • The designation for missing values, given as -9.0 in the original files, was changed to -999.9 for the consistency with other oceanographic data sets. 5. HOW TO OBTAIN THE DATA AND DOCUMENTATION (frrom CDIAC) This data base (NDP-082) is available free of charge from CDIAC. The complete documentation and data can be obtained from the CDIAC oceanographic Web site (http://cdiac.ornl.gov/oceans/doc.html), through CDIAC's online ordering system (http://cdiac.ornl.gov/pns/how_order.html), or by contacting CDIAC (see below). The data are also available from CDIACs anonymous file transfer protocol (FTP) area via the Internet. Please note that, to access these files, your computer needs tomust have FTP software loaded on it (this is built in to most newer operating systems). Use the following commands to obtain the data base. ftp cdiac.ornl.gov or >ftp 160.91.18.18 Login: anonymous or ftp Password: your e-mail address ftp> cd pub/ndp082/ ftp> dir ftp> mget (files) ftp> quit Contact information: Carbon Dioxide Information Analysis Center Oak Ridge National Laboratory P.O. Box 2008 Oak Ridge, Tennessee 37831-6335 U.S.A. Telephone: (865) 574-3645 Telefax: (865) 574-2232 E-mail: cdiac@ornl.gov Internet: http://cdiac.ornl.gov/ 6. REFERENCES Armstrong, F. A. J., C. R. Stearns, and J. D. H. Strickland. 1967. The measurement of upwelling and subsequent biological processes by means of the Technicon AutoAnalyzer and associated equipment. Deep-Sea Research 14:381-9. Atlas, E. L., S. W. Hager, L. I. Gordon, and P. K. Park. 1971. A Practical Manual for Use of the Technicon AutoAnalyzer in Seawater Nutrient Analyses (revised). Technical Report 215, Reference 71-22, Oregon State University, Department of Oceanography, Oregon. Bernhardt, H. and A. Wilhelms. 1967. The continuous determination of low- level iron, soluble phosphate and total phosphate with the AutoAnalyzer. Technicon Symposia 1:385-9. Bradshaw, A. L. and P. G. Brewer. 1988. High-precision measurements of alkalinity and total carbon dioxide in seawater by potentiometric titration: 1. Presence of unknown protolyte (s). Marine Chemistry 28:69-86. Brewer, P. G., C. Goyet, and D. Dyrssen. 1989. Carbon dioxide transport by ocean currents at 25° N latitude in the Atlantic Ocean. Science 246:477-79. Bryden, H. L., and M. M. Hall. 1980. Heat transport by ocean currents across 25° N latitude in the North Atlantic Ocean. Science 207:884. Carpenter, J. H. 1965. The Chesapeake Bay Institute technique for the Winkler dissolved oxygen method. Limnology and Oceanography 10:141-3. Chipman, D. W., J. Marra, and T. Takahashi. 1993. Primary production at 47° N and 20° W in the North Atlantic Ocean: A comparison between the 14C incubation method and the mixed layer carbon budget. Deep-Sea Research 40:151-69. Clayton, T. and R. H. Byrne. 1993. Calibration of m-cresol purple on the total hydrogen ion concentration scale and its application to CO2-system characteristics in seawater. Deep-Sea Research 40:2115-29. Culberson, C. H., G. Knapp, M. Stalcup, R. T. Williams, and F. Zemlyak. 1991. A Comparison of Methods for the Determination of Dissolved Oxygen in Seawater. WHP Office Report, WHPO 91-2. WOCE Hydrographic Program Office, Woods Hole, Mass. U.S.A. DOE (U.S. Department of Energy). 1994. Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in Seawater. Version 2.0. ORNL/CDIAC-74. A.G.Dickson and C. Goyet (eds.). Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Gordon, L. I., J. C. Jennings, Jr., A. A. Ross, and J. M. Krest. 1992. A Suggested Protocol for Continuous Flow Automated Analysis of Seawater Nutrients (Phosphate, Nitrate, Nitrite and Silicic Acid) in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study. Grp. Tech. Rpt. 92-1. Chemical Oceanography Group, Oregon State University, College of Oceanography, Oregon, U.S.A. Gordon, L. I., J. C. Jennings, Jr., A. A. Ross, and J. M. Krest. 1994. A Suggested Protocol for Continuous Flow Automated Analysis of Seawater Nutrients (Phosphate, Nitrate, Nitrite Aand Silicic Acid) in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study. In WOCE Operations Manual. WHP Office Report WHPO 91-1. WOCE Report No. 68/91. Revision 1. Woods Hole, Mass., U.S.A. Hager, S. W., E. L. Atlas, L. I. Gordon, A. W. Mantyla, and P. K. Park. 1972. A comparison at sea of manual and autoanalyzer analyses of phosphate, nitrate, and silicate. Limnology and Oceanography 17:931-7. Holfort, J., K. M. Johnson, B. Schneider, G. Siedler, and D. W. R. Wallace. 1998. Meridional transport of dissolved inorganic carbon in the South Atlantic Ocean. Global Biogeochemical Cycles 12:479-499. Huffman, E. W. D., Jr. 1977. Performance of a new automatic carbon dioxide coulometer. Microchemical Journal 22:567-73. Johnson, K. M., A. E. King, and J. McN. Sieburth. 1985. Coulometric TCO2 analyses for marine studies: An introduction. Marine Chemistry 16:61-82. Johnson, K. M., P. J. Williams, and L. Brandstroem, and J. McN. Sieburth. 1987. Coulometric TCO2 analysis for marine studies: Automation and calibration. Marine Chemistry 21:117-33. Johnson, K. M., and D. W. R. Wallace. 1992. The Single-operator Multiparameter Metabolic Analyzer for Total Carbon Dioxide with Coulometric Detection. DOE Research Summary No. 19. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A. Johnson, K. M., K. D. Wills, D. B. Butler, W. K. Johnson, and C. S. Wong. 1993. Coulometric total carbon dioxide analysis for marine studies: Maximizing the performance of an automated gas extraction system and coulometric detector. Marine Chemistry 44:167-87. Johnson, K. M., D. W. R. Wallace, R. J. Wilke, and C. Goyet. 1995. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Meteor Cruise 15/3 in the South Atlantic Ocean (WOCE Section A9, February-March 1991). ORNL/CDIAC-82, NDP-051. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn. Johnson, K. M., B. Schneider, L. Mintrop, and D. W. R. Wallace. 1996. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Meteor Cruise 18/1 in the North Atlantic Ocean (WOCE Section A1E, September 1991). NDP-056. Carbon Dioxide Information Analysis Center (CDIAC), Oak Ridge National Laboratory, Oak Ridge, Tenn. Johnson, K. M., B. Schneider, L. Mintrop, and D. W. R. Wallace. 1998a. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Meteor Cruise 22/5 in the South Atlantic Ocean (WOCE Section A10, December 1992- January 1993). ORNL/CDIAC-113, NDP-066. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn. 49 pp. Johnson, K. M., A. G. Dickson, G. Eischeid, C. Goyet, P. R. Guenther, R. M. Key, F. J. Millero, D. Purkerson, C. L. Sabine, R. G. Schotle, D. W. R. Wallace, R. J. Wilke, and C. D. Winn. 1998b. Coulometric total carbon dioxide analysis for marine studies: Assessment of the quality of total inorganic carbon measurements made during the U.S. Indian Ocean CO2 Survey 1994-1996. Marine Chemistry 63:21-37. Johnson, K. M., M. Haines, R. M. Key, C. Neill, B. Tilbrook, R. Wilke, and D.W.R. Wallace. 2001. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Knorr Cruises 138-3, -4, and -5 in the South Pacific Ocean (WOCE Sections P6E, P6C, and P6W, May 2 - July 30, 1992). ORNL/CDIAC-132, NDP-077. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn. 53 pp. Knapp, G. P., M. C. Stalcup, and R. J. Stanley. 1990. Automated Oxygen and Salinity Determination. Woods Hole Oceanographic Institution Technical Report No. WHOI-90-35. Woods Hole Oceanographic Institution, Woods Hole, Mass., U.S.A. Marinenko, G. and J. K. Taylor. 1968. Electrochemical equivalents of benzoic and oxalic acid. Analytical Chemistry 40:1645-51. Millard, R. C. and K. Yang. 1993. CTD Calibration and Processing Methods Used at Woods Hole Oceanographic Institution. Woods Hole Oceanographic Institution Technical Report. WHOI 93-44. Woods Hole Oceanographic Institution, Woods Hole, Mass., U.S.A. Millero, F. J., and A. Poisson. 1981. International one-atmosphere equation of state for seawater. Deep-Sea Research 28:625-29. Millero, F. J., J. Z. Zhang, S. Fiol, S. Sotolongo, R. Roy, K. Lee, and S. Mane. 1993a. The use of buffers to measure the pH of seawater. Marine Chemistry 44:143-152. Millero, F. J., J. Z. Zhang, K. Lee, and D. M. Campbell. 1993b. Titration alkalinity of seawater. Marine Chemistry 44:153-156. Millero, F. J., F. Huang, M. Galanter, J. Goen, C. Sabine, C. Thomas, and R. Rotter. 1999. The Total Alkalinity of North Atlantic Waters. University of Miami Technical Report, No. RSMAS-99-002. University of Miami, Miami, Florida. Roemmich, D., and C. Wunsch. 1985. Two transatlantic sections: Meridional circulation and heat flux in the subtropical North Atlantic Ocean. Deep- Sea Research 32:619-64. Schlitzer, R. 2001. Ocean Data View. http://www.awi-bremerhaven.de/GEO/ODV. Online publication. Alfred-Wegener-Institute for Polar and Marine Research. Bremerhaven, Germany. Strickland, J. D. H. and T. R. Parsons. 1972. The Practical Handbook of Seawater Analysis. Bulletin 167, Fisheries Research Board of Canada, 310 pp. Takahashi, T., D. W. Chipman, S. Rubin, J. Goddard, and S. C. Sutherland. 1998. Measurements of the Total CO2 Concentration and Partial Pressure of CO2 in Seawater during WOCE Expeditions P-16, P-17 and P-19 in the South Pacific Ocean, October, 1992 - April, 1993. Final Technical Report of Grant No. DE-FGO2-93ER61539 to U. S. Department of Energy, Lamont-Doherty Earth Observatory, Palisades, N.Y. 10964, pp. 124. Taylor, J. K. and S. W. Smith. 1959. Precise coulometric titration of acids and bases. Journal of Research of the National Bureau of Standards 63A:153-9. UNESCO (United Nations Educational, Scientific, and Cultural Organization). 1981. Background papers and supporting data on the practical salinity scale, 1978. UNESCO Technical Papers in Marine Science 37:144. Wallace, D. W. R. 2002. Storage and transport of excess CO2 in the oceans: The JGOFS/WOCE Gglobal CO2 survey. In J. Church, G. Siedler, and J. Gould (eds.). Ocean Circulation and Climate, Academic Press, 489-521. Wilke, R. J., D. W. R. Wallace, and K. M. Johnson. 1993. A water-based, gravimetric method for the determination of gas sample loop volume. Analiytical Chemistry 65:2403-2406 Youden, W. J. 1951. Statistical Methods for Chemists. Wiley, New York. 7. DATA PACKAGE DESCRIPTIONS 7.1 File Content and Format Descriptions This section describes the content and format of each of the data files that constitute NDP-082 (see Table 7). Table 7. Content, size, and format of data files _____________________________________________________________________ File number, name, and description File size in bytes ---------------------------------- -------------------------- 1-2. ndp082.txt 106,779 ndp082.pdf 5,101,440 A detailed description of the cruise network, and oceanographic data files in simple text and PDF formats 3-6. a20sta.dat 7,838 a22sta.dat 6,926 a24sta.dat 12,702 ar24sta.dat 15,438 A listing of the station locations, sampling dates, and sounding bottom depths for each station of WOCE Sections A20, A22, A24, and AR24 in the original WOCE format 7-10. a20.dat 476,060 a22.dat 403,860 a24.dat 657,510 ar24.dat 598,397 Hydrographic, carbon dioxide, and chemical data from all stations occupied on WOCE Sections A20, A22, A24, and AR24. The files are reported in the original WOCE format 11-14. a20_hy1.csv 857,377 a22_hy1.csv 701,706 a24_hy1.csv 1,050,215 ar24_hy1.csv 932,634 Hydrographic, carbon dioxide, and chemical data from all stations occupied on WOCE Sections A20, A22, A24, and AR24. The files are provided as WOCE exchange format files [comma-separated value (CSV) files]. 15. NA_ODV_data.txt 2,410,877 The Ocean Data View Sspread Ssheet data file. The file consists of data from all four sections of the North Atlantic survey Total size 13,339,759 _____________________________________________________________________ 7.2 Descriptions of Variables The station inventory file (*sta.dat) variables are defined as follows: EXPOCODE Character (A10) expedition code of the cruise SECT Character (A4) WOCE section number STNBR Numeric (I3) station number CAST Numerixc (I1) cast number DATE Character (A10) sampling date (month/day/year) TIME Character (A4) sampling time [Greenwich mean time (GMT)] LATITUDE Numeric (F7.3) latitude of the station (in decimal degrees; negative values indicate the Southern Hemisphere) LONGITUDE Numeric (F8.3) longitude of the station (in decimal degrees; negative values indicate the Western Hemisphere) DEPTH Numeric (I4) sounding depth of the station (in meters) The data file (*.dat) variables are defined as follows: STNBR Numeric (I3) station number CASTNO Numeric (I1) cast number SAMPNO Numeric (I2) sample number BTLNBR* Numeric (I2) bottle number CTDPRS Numeric (F7.1) CTD pressure (dbar) CTDTMP Numeric (F7.4) CTD temperature (°C) CTDSAL* Numeric (F7.4) CTD salinity CTDOXY* Numeric (F7.1) CTD oxygen (µmol/kg) THETA Numeric (F7.4) potential temperature (°C) SALNTY* Numeric (F9.4) bottle salinity OXYGEN* Numeric (F7.1) oxygen concentration (µmol/kg) SILCAT* Numeric (F7.2) silicate concentration (µmol/kg) NITRAT* Numeric (F7.2) nitrate concentration (µmol/kg) NITRIT* Numeric (F7.2) nitrite concentration (µmol/kg) PHSPHT* Numeric (F7.2) phosphate concentration (µmol/kg) CFC11* Numeric (F8.3) chlorofluorocarbon 11 (picamole/kg) CFC12* Numeric (F8.3) chlorofluorocarbon 12 (picamole/kg) TCARBN* Numeric (F7.1) total carbon dioxide concentration (µmol/kg) ALKALI* Numeric (F7.1) total alkalinity (µmol/kg) PCO2* Numeric (F7.1) partial pressure of CO2 (?atm) PH* Numeric (F8.3) pH QUALT1 Character (A15) 15-digit character variable that contains data-quality flag codes for parameters underlined with asterisks (*******) in the file header ___________________________________ *Variables that are underlined with asterisks in the data files header indicate they have a data-quality flag. Data-quality flags are defined as follows: 1 = sample for this measurement was drawn from water bottle but analysis was not received 2 = acceptable measurement 3 = questionable measurement 4 = bad measurement 5 = not reported 6 = mean of replicate measurements 9 = sample not drawn for this measurement from this bottle CCHDO DATA PROCESSING NOTES Date Contact Data Type Event Summary ---------- ---------- -------------- --------------- ---------------------- 1999-09-29 Anderson SUM Update Needed being reformatted I have added Mike McCartney's Knorr cruise to the AR24's. Expocode is 316N147_2. Dates are (from the sum file) Nov 2 - Dec 3, 1996. Chi Sci was Mike McCartney of WHOI. Currently we just have a sumfile that is being passed off to Sarilee for reformatting. I have requested the bottle and ctd data from Ruth Curry as per Lynne's request. 2000-03-15 McCartney CTD/BTL/SUM Submitted Data available online. Take the data from the subpolar ACCE site. 2000-03-16 Curry CTD/BTL/SUM Data are Public Data are public Yes. We consider these to be in the public domain now. 2000-03-21 Chapman Tracer Not Measured See note: I asked Mke Mccartney what, if any data were taken on AR24 other than CTDO data. He said that no tracer data were collected on either of these repeat cruises, and that nutrients were collected only on the first of them. 2001-08-21 Uribe SUM Website Updated SUM file reformatted Sumfile was missing WOCE SECT names. It was filled in with AR24. Extra space in header was removed. Sumfile now passes whpo format checks. 2002-01-17 Uribe CTD Website Updated Exchange file online CTD has been converted to exchange using the new code and put online. 2002-05-01 Bartolacci CTD/BTL/SUM Update Needed Need WOCE fmttng. BOT in multple files. CTD exchg made. Still no DOC from Curry. WOCE frmt all files. Create BOT exchg. Write Curry for DOC. 2002-05-23 Bartolacci CTD/SUM Website Updated Exchng files corrected As per email from Raymond Pollard an error in the summary file longitude for the BE code of station 141 has been corrected. Minutes were changed from 19 to 15. This error was also corrected in CTD exchange file for station 141. The NetCDF file for the CTD has not been remade at this time. Current online index.htm page has also been updated to reflect recent changes in all files. 2003-06-18 Bartolacci BTL Data Reformatted/OnLine It was brought to our attention that the bottle file for this cruise was never completely reformatted. This was because we never heard from McCartney the Chief Scientist. However we did recieve directions on reformatting from Ruth Curry for this bottle file. McCartney was supposed to follow up. This has not happened and neither Curry nor McCartney have sent a doc file as of this date. I have reformatted the bottle file according to Curry's instructions. **NOTE** All values for oxygen are in ML/L and all values for nutrients are in UMOL/L at this time. No conversions have been performed during reformatting. • Concatenated all 3 .sea files together. (s1t60.sea, s61t131.sea, s131t190.sea) new file called ar24_allstns.sea which was copied to ar24_ahy.txt. • Added WHF to bottle file numbers for stations 1-60 to match all other stations' bottle file numbers. • Realigned the SILCAT data column. • Changed all parameter units to uppercase. • Changed expocode from 31KN47 to 316N147_2 to match sumfile. • Added name/date stamp. • Ran wocecvt with no errors. • Created exchange and netCDF files and checked files in JOA. No apparent errors were produced. • Created bottle file inventory file with no apparent errors. • placed all new files on line and regenerated web pages. 2003-06-20 Sanborn Cruise Report Submitted Preliminary This is an internal report and should not be published. 2003-06-23 Bartolacci BTL Website Updated files online I have concatenated and formatted the bottle file for this cruise. File was format checked, units for oxygen and nutrients were converted and exchange, inventory and netcdf files were created. Files were checked with JOA and placed online. Web page files were updated. Notes on formatting were sent to Jerry Kappa. NOTE no documentation file has yet been received for this cruise. Date Contact Data Type Event Summary ---------- ---------- -------------- --------------- ---------------------- 2003-06-24 Bartolacci NUTs Update Needed Questions about converting nutrients Bottle file contains all nutrients in UMOL/L and O2 in ML/L. We've never heard from Mike McCartney on any questions regarding the files and Ruth Curry was the one who offered help on reformatting although it wasn't her cruise. I recall just using a piece of code from Sarilee for converting CTD oxygens, but is there something for converting bottle oxygens too? and what should I do about the nutrient units? It converted to exchange with the current precision and units, should I put up what we have right now? 2003-07-01 Bartolacci CTDSAL/OXY Website Updated Q1 flags removed As per Alex Kozyr and Jim Swift, I have removed the Q1 flags associated with CTD salinity and oxygen. Previously, these bytes were set to 1& with no DQE information available or pending. Asterisks were also removed from the appropriate headers. All files were regenerated, format tested and placed online. As per Alex Kozyr's inquiry regarding the the Q1 flags for CTD salinity and oxygen (they were both set to 1 in the bottle file), I have reformatted the bottle file at Jim Swift's request. • Removed the Q1 bytes for CTD salinity and oxygen. Removed the asterisks under the headers corresponding to these values. • Reran wocecvt with no errors • Added name/date stamp. • Regenerated exchange, netCDF and inventory files with no errors produced. • loaded files into JOA with no errors. • replaced all current files, moved old files to original directory. 2003-07-11 Bartolacci CTDOXY/ALK/CO2 Website Updated ALK & CO2 flags corrected After recommendation from A. Kozyr to edit specific flags for alkalinity and carbon parameters, a new file was sent by Kozyr containing these corrected flags. This new bottle file was checked then used to generate new exchange and netcdf files. New files were tested with JOA and placed online. Old files were renamed and moved to the original directory. 2003-07-11 Kozyr CTDOXY/ALK/CO2 Update Needed Correct ALK & CO2 flags The CTD oxygen of station No.1 should be changed all to -9.00, as we do not have flags for it anymore, otherwise they would make no sense. Could you change all ALKALI and TCARBN flags were no data was measured from 1 to 9. In the following instances the flag 4 should be changed to 5: sta-cast-sample 11-1-18 ALKALI 16-1-23 TCARBN 16-1-4 TCARBN 16-1-3 TCARBN 28-1-3 TCARBN 30-1-1 TCARBN 47-1-18 ALKALI 47-1-12 ALKALI 49-1-16 TCARBN 51-1-8 ALKALI 51-1-1 TCARBN 71-1-7 TCARBN 74-1-6 TCARBN 97-1-21 ALKALI - also look at the nutrients values, they all should be -9.00 97-1-20 ALKALI 107-1-4 TCARBN 118-1-18 TCARBN 118-1-3 ALKALI 120-1-24 TCARBN 120-1-21 ALKALI 123-1-7 ALKALI Date Contact Data Type Event Summary ---------- ---------- -------------- --------------- ---------------------- 2008-08-25 Berys sum Data Update Fixed lat/lon errors In regards to a couple of errors in station locations in the sum file for AR24, expocode 316N147_2, Matthew and I made the following changes on Friday, 8/22/08. Station: 66 Cast: 1 Time: 09:32 Error: Longitude read: 63 33.92 W Change: The "63" was changed to "36" Station: 139 Cast: 1 Time: 20:44 Error: Lattitude read: 55 21.33 N Change: The "55" was changed to "53" 2008-09-09 Kappa Cruise Report Website Updated CDIAC Data report (NDP 082)