Plants, soil and the sea trap about half of the CO2 released by human activities. The waters around Antarctica are the largest oceanic sink, accounting for about 15% of CO2 absorbed.
But it seems rising temperatures and ozone layer depletion may be strengthening winds in the region, bringing more carbon-rich water to the surface.
"This is the first time that we’ve been able to say that climate change itself is responsible for the saturation of the Southern Ocean sink," says Corinne Le Quéré, a climatologist at the University of East Anglia and British Antarctic Survey. "This is serious. All climate models predict that this kind of ‘feedback’ will continue and intensify during this century."
Rising CO2 levels were expected to prompt greater uptake, but weather station measurements analysed by Dr Le Quéré and her team show absorption has fallen slightly since 1981.