Caldeira Lab Research:Ocean acidification and ocean carbon cycle

The role of the Southern Ocean in uptake and storage of anthropogenic carbon dioxide

Ken Caldeira & Phillip B. Duffy

In the past, the role of the Southern Ocean in the uptake of emitted carbon dioxide has been the subject of much debate. Through both models and observation, it is shown here that the Southern Ocean in fact stores very little anthropogenic carbon dioxide. However, the carbon flux into it is quite high, indicating a high level of uptake despite the low level of storage.

Caldeira, K., and P.B. Duffy, The role of the Southern Ocean in uptake and storage of anthropogenic carbon dioxide, Science 287, 620–622, 2000.

Carbon dioxide storage in the Southern ocean: observed (left) and modeled (right) concentrations of CO2 in the Indian Ocean (A & D), 92°E in 1995 (B & E) and the western Atlantic in 1995.  Both the observed and modeled estimates show fairly little CO2 storage.

Carbon flux in the global ocean: the amount of CO2 flux from the atmosphere to the ocean shown for various oceanic locations. Despite its low storage levels, CO2 flux is highest in the Southern Ocean.


An ocean-climate model that shows high fluxes of anthropogenic carbon dioxide into the Southern Ocean, but very low storage of anthropogenic carbon there, agrees with observation-based estimates of ocean storage of anthropogenic carbon dioxide. This low simulated storage indicates a subordinate role for deep convection in the present-day Southern Ocean. The primary mechanism transporting anthropogenic carbon out of the Southern Ocean is isopycnal transport. These results imply that if global climate change reduces the density of surface waters in the Southern Ocean, isopycnal surfaces that now outcrop may become isolated from the atmosphere, tending to diminish Southern Ocean carbon uptake.