Decreasing importance of carbon-climate feedbacks in the Southern Ocean in a warming climate

The Southern Ocean is an important CO₂ sink, mitigating climate change, but its future evolution is uncertain due to the confounding effects of stratospheric ozone recovery and climate change on ocean circulation. Using an Earth System Model, we quantify the relative influence of ozone-depleting substances and greenhouse gas emissions on this sink from 1950 to 2100. Ozone effects dominated changes in ocean circulation during 1950–2000, but not this century, implying that past trends cannot serve as proxies for future changes. Despite substantial future circulation changes induced by climate change, their effect on the CO₂ sink decreases over the 21st century because of compensating factors. Thus, the Southern Ocean is unlikely to be a major future source of amplifying carbon-climate feedbacks this century.