Etcheto, J., J. Boutin, Y. Rangama and L. Merlivat

Laboratoire d'Océanographie Dynamique et de Climatologie, Paris, France, Tel: 33 1 44 27 70 71, Fax: 33 1 44 27 38 05 and E-mail: je@lodyc.jussieu.fr

Recent results from CARIOCA drifters in the Southern Ocean

The oceanic CO₂ partial pressure (pCO₂) in the Southern Ocean is studied using CARIOCA autonomous drifters measuring pCO₂, Sea Surface Temperature (SST), Sea Surface Salinity (SSS, for three of them), wind speed, atmospheric pressure and fluorescence. Five of them were deployed in the Southern Ocean: three in the central Indian Ocean (45°S 73°E) in November 2001 and January 2002, two south of Tasmania (49°S 140°E) foreseen in February 2003. They drifted eastward for several months (1, 3 and 6 months for the first three) exploring large sectors of the Southern Ocean (from 73°E to 143°E in 6 month). The measured pCO₂ is nearly always below equilibrium and varies in a restricted range (usually between 340 and 370 µatm, average value close to 350 µatm) in the subantarctic zone (SAZ) indicating that thermodynamical effect is nearly compensated by mixing. The resulting average air-sea flux is around 3.8 mmol m^-2 day^-1. The pCO₂ variations, mostly observed close to subtropical front, are interpreted using the SST and SSS measured by the buoys as well as satellite SST and chlorophyll observations to image the region. We explain the observations in terms of warming and water masses mixing depending on the zone explored. The pCO₂ measured in the SAZ between 105°E and 145°E exhibit a SST dependence close to the one observed further east by the AESOP and Astrolabe campaigns.