A window for carbon uptake in the southern subtropical Indian Ocean

Atmospheric CO 2 sinks in the southern Indian Ocean was examined for their seasonal, interannual and interdecadal variability. Two distinct zones of CO 2 uptake are identified; located in the 15°S–35°S band is the northern box where CO 2 uptake is dominated by the solubility pump, and in the latitudinal range of 35°S–50°S is the southern box where both the solubility and biological pump are equal players. The anthropogenic CO 2 inventories appear to be a result of deepening subduction of CO 2 and subsequent invasion into the northern domain. The seasonal and interannual variability of CO 2 sinks to the north are rather surface trapped, while the deep CO 2 variability is found to be coherent with the atmospheric forcing, consistent with decadal wind stress curl anomalies. This is a step towards separating the secular trends of deep ocean CO 2 from its natural variability in the analysis region.