A. CRUISE NARRATIVE: ISS02, IR01W, IR03N (WESTERN ARABIAN SEA) A.1. HIGHLIGHTS WHP CRUISE SUMMARY INFORMATION WOCE section designation ISS02, IR01W, IR03N Expedition designation (EXPOCODE) 06MT32_1 Chief Scientist/affiliation FRIEDRICH SCHOTT/IfM Kiel* Dates 1995 MAR 23 - 1995 APR 26 Ship RV METEOR Ports of call Djibouti to Muscat, Oman Number of stations CTD: 91 XBT: 45 25°N Geographic boundaries 42°E 62°E 2°S Floats and drifters deployed 0 Moorings deployed or recovered ? Contributing Authors Prof. Friedrich Schott Monika Rhein Olaf Plähn ___________________________________________________________________________ *Prof. Friedrich Schott Institut fuer Meereskunde Duesternbrooker Weg 20 24105 Kiel Germany Tel. +49-431-600-4100 Fax. +49-431-600-4102 e-mail: fschott@ifm.uni-kiel.de A.2. SCIENTIFIC PROGRAM The cruise was designated to derive hydrographic data in the Arabian Sea as part of the WOCE-program and to deploy several moorings in the western Arabian Sea. A.3. PARTICIPANTS Prof. Friedrich Schott Chief scientist IfM Kiel fschott@ifm.uni-kiel.de --------------------------------------------------------------- Monika Rhein Chlorofluorocarbons IfM Kiel monika.rhein@io-warnemuende.de --------------------------------------------------------------- Olaf Plähn Chlorofluorocarbons IfM Kiel oplaehn@ifm.uni-kiel.de --------------------------------------------------------------- Martina Elbrächter CFC-Lab IfM Kiel melbraechter@ifm.uni-kiel.de IfM Kiel: Institut für Meereskunde, 24105 Kiel, Germany B. CHLOROFLUOROCARBONS (Monika Rhein and Olaf Plähn) Region: Arabian Sea, Gulf of Aden, Gulf of Oman, SAMPLE COLLECTION AND TECHNIQUE All samples were collected from 10 L Niskin bottles. The bottles had been cleaned prior to the cruise using isopropanol. All 'O' rings, valves, and taps were removed, washed in isopropanol and baked in a vacuum oven for 24 hours. The rubber bands on all bottles were replaced by stainless steel springs. The personnel for all water sampling and handling procedures at the bottles wore one-way gloves to protect the valves from grease. About 100 mL of water were taken from the water bottles with gastight glass syringes (Becton and Dickinson). Then 15-25 mL of the samples were transfered to a purge and trap unit and analyzed on board following the procedures described in Bullister and Weiss [1988]. The CFCs were separated on a packed stainless steel column filled with Porasil C and detected with an Electron Capture Detector (ECD). The carrier gas was ECD pure Nitrogen, which was additionally cleaned by molsieves (13X mesh 80/100). The calibration was done using a standard gas with near air concentrations to convert the ECD signal in concentrations. The CFC values are reported in pmol kg-1 on the SIO93 scale (R. Weiss, SIO). FIGURE 1: Accuracy of the CFC-12 component; replicate samples plotted vs profile number. PERFORMANCE During the cruise M32/1 the Kiel CFC system worked continuously. Both CFC components CFC-11 and CFC-12 had been sampled on 75 CTD stations and 880 water were analyzed. The accuracy was checked by measuring about 220 water samples twice or more. It was found to be for CFC-12 1.3% or 0.005 pmol kg-1 (Figure 1). The CFC-11 component could not be analyzed successfully (see para 'Contamination'). The mean blank of the sample transfer and the measurement procedure was determined by degasing 1-2 mL of CFC free deep water. During the cruise it was in the order of 0.005 pmol kg-1 for CFC-12. Furthermore, CFC free water was created by degasing 5 L of seawater with ECD-pure nitrogen gas, to determine blanks of the measurement system and the syringes. Analysis of 25 mL of blankwater resulted in concentrations below 0.007 pmol kg-1 for both components. The efficiency of the ECD was stable for the CFC-12 component. During the cruise the efficiency decreased only 20% (Figure 2). To correct the temporal drift of the ECD, a calibration curve with seven different gas volumes was taken before and after each station. The temporal change between two calibration curves was assumed to be linear in time. CFC concentrations were calculated by using the two neighboured points, supposing that the calibration curve is linear between these points. FIGURE 2: The temporal evolution of the ECD-efficiency during the cruise for the 0.5 mL volume (small) and the 2 mL volume (large). CONTAMINATION During the whole cruise, the CFC-11 measurements were deteriorated by contami- nation of the water bottles. Neither the numerous cleaning procedures of the water bottles/rosette nor the replacement ofwater bottles did remove the exceptionally high and variable contamination for CFC-11. For instance, the CFC-11 saturation in surface water was between 135-180%. The CFC-12 concentrations presumably remained unaffected, with surface saturations between 95 and 110%. On some stations, the CFC-12 peaks were disturbed by the high N2O levels, these data were removed. COMMENTS The CFC concentrations decrease exponentially from the surface to about 1000 m depth. At greater depths, CFC concentrations were below detection limit (Figure 3). In the western Gulf of Oman (stations 210-224) the CFC-12 concentrations in the density range of the PGW (Persian Gulf Water, 26.3