Work Package 5: Southern Ocean observations and processes

Leader: Jaqueline Boutin

Objectives
- To assess air-sea CO2 flux and its space and time variability in specific sink regions of the
Atlantic and Indian sectors of the Southern Ocean. We will concentrate on the sub-Antarctic
zone, the region of main formation of intermediate water and expected to be a major sink region
for atmospheric CO2.
- To provide regional air-sea fluxes at monthly time scales to constrain atmospheric inverse
modelling.

Description of work
- Measure pCO2 and key related variables (sea surface temperature, sea surface salinity, wind
speed, fluorescence, atmospheric pressure) during 3 years using 8 CARIOCA2 drifters (1-year
lifetime, autonomous instruments), launched from the Atlantic sector of the Southern Ocean and
drifting eastwards into the Indian Ocean sector. These measurements will be completed by regular
observations of surface properties acquired during regular cruises of Antarctic supply vessels
and research ship Hesperides, , Polarstern and Marion Dufresne in these sectors. (partners 3, 5,
7)
- Mechanistic understanding of the relevant processes controlling observed pCO2 variability will
be performed using remote sensing measurements of SST and ocean colour. The region will be
divided in biogeochemical provinces characterized by varying dominant factors controlling
pCO2. Thence empirical relationships between pCO2, SST and ocean colour established in each
province will be used to map oceanic pCO2 at regional scale. Air-sea flux will be derived using
CO2 exchange coefficient derived from satellite wind speed. (partner 7)
- Seasonal to interannual variability of air-sea CO2 fluxes will be studied in relation with depth
profiles of carbon parameters measured during historical and present OISO cruises in the Indian
Ocean (partner 7)