The Southern Ocean, one of the planet's biggest carbon sinks, is almost totally saturated, according to research published in the journal Science.

Scientists at the University of East Anglia (UEA) joined forces with the British Antarctic Survey (BAS) and the Max Planck institute for a four year study of the ocean around the southern continent. They found that increased winds over the Southern Ocean has triggered a release of stored CO 2 .

The researchers say the increase in wind in the region has been triggered by ozone depletion and greenhouse gas emission.

"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," said lead author Dr Corinne Le Quéré of UEA and BAS.

"The Earth's carbon sinks – of which the Southern Ocean accounts for 15 per cent – absorb about half of all human carbon emissions. With the Southern Ocean reaching its saturation point more CO 2 will stay in our atmosphere," Le Quéré explained.

A carbon sink - be it a forest, ocean, methane crystals trapped in ice sheets, or a peat bog in Siberia - locks carbon out of the atmosphere so that it doesn't contribute to the greenhouse effect.

Since the industrial revolution, the Earth's oceans have absorbed as much as 500 gigatons of the carbon generated by human activity. Professor Chris Rapley, director of British Antarctic Survey described the possibility that the strongest of these oceanic sinks is weakening as "a cause for concern".

Most climate models predict that this kind of negative feedback will intensify this century, Le Quéré says.

As well as having implications for how easy it will be to stabilise the amount of carbon in the atmosphere, the research also suggests the Southern Ocean will reach dangerous levels of acidity sooner than expected: bad news for local marine life. ®