Measurements of CFCs and CO2 during the French Confluence Expedition in the Western South Atlantic Ocean

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9302150 TAKAHASHI CFCs (CFC-11., -12 and -113) and CO2 (total CO2 concentration and pCO2) will be measured in seawater during the French CONFLUENCE program in the western South Atlantic Ocean between 35.0S and 43.5S in collaboration with Dr. Veronique Garcon of Observatoir Midi- Purenees, CNRS, Toulouse, and Dr. Christine Provost of Universite P.-et-M. Curie, Paris. The French Research Vessel Le Suroit has been scheduled for the expedition, December 1993, through January 1994, and the ship's time and hydrographic program have been funded by CNRS. The Scientific objectives of the proposed study are as follows: 1) Investigate ventilation of the South Atlantic subtropical gyre thermocline waters by the mode waters using CFCs and minimum potential vorticity as tracers. Since near surface waters in the confluence zone are highly undersaturated with respect to atmospheric CO2, the CO2 uptake and transport by the mode waters can be estimated using these chemical and physical tracers. 2) In intermediate depths, a CFC maximum is associated with the salinity minimum of AAIW. The circulations pathway and time of formation of AAIW will be investigated using CFCs. 3) The data obtained during the 1988-89 SAVE program show that the western boundary undercurrent which flows poleward along the Argentine continental slopes at a depth of about 2000 meters exhibits a local minimum in CO2 and CFC. These signals have been traced from 10S to about 35S. Temporal and spatial changes in the CFC and CO2 signals will help to understand the spreading processes of NADW in the South Atlantic. 4) High CFC values have been detected in bottom waters entering into the Argentine Basin from the South Georgia Basin. These CFCs will be measured in the bottom water in order to learn its spreading pathway in the Argentine Basin.