Scientists put great hopes on the Ocean to ease the effects of dumping too much global warming producing carbon dioxide (CO2), by absorbing and storing it at great depths. These carbon sinks are crucial coping with the excess of CO2 from the atmosphere, as they slow down the greenhouse effect.
This effect had been predicted by climate scientists and is taken into account - to some extent - by climate models. But new observations show a decline of Antarctica's Southern Ocean carbon "sink", pointing to a higher atmospheric CO2 level 40 years before calculated.
Half of the CO2 expelled into the atmosphere is absorbed by the oceans and the plants through photosynthesis, each process sharing about 25 %, but the Southern Ocean is believed to make 15 % of all carbon absorptions.
Scientists believed that the ocean could cope with an increase of released CO2 amounts, sinking more of it as its concentration grows. Still, the ocean was expected to be overcome by these, but after 2050.
But a team of the British Antarctic Survey (BAS) led by Corinne Le Quere proved the precocity of this by collecting atmospheric CO2 data from 11 stations in the Southern Ocean and other 40 worldwide.
"Ever since observations started in 1981, we see that the sinks have not increased [in their absorption of CO2]," LeQuere told the BBC's Science in Action programme.
"They have remained the same as they were 24 years ago even though the emissions have risen by 40%."
This decline in the Southern Ocean absorption could be blamed on increased windiness since 1958, due to two factors: regional temperature changes due to the ozone decrease in the upper atmosphere and the recent climate change, rising more the temperature in the tropics more than the Southern Ocean.
"As the winds increase, the water in the ocean mixes more. The CO2 that would normally be in the deep ocean and would just stay there instead gets brought up to the surface and outgasses to the atmosphere." explained Le Quere.
Increased CO2 is also acidifying the surface waters of oceans, harming many sensitive species like coral.
"The problem is that the extra CO2 from human emissions stays in the surface ocean and does not get removed to deep waters. So the problem gets worse, because the biological organisms affected by ocean acidification live, of course, at the surface where there is sunlight." said Dr Le Quere.