Southern Ocean saturated

Science doi: 10.1126/science.1136188 (2007)

Credit: BAS

Around half of all human-produced CO₂ is removed from the atmosphere by the oceans, slowing global warming. Now, a study shows that the Southern Ocean, one of the largest carbon sinks, is absorbing less CO₂ than expected relative to atmospheric levels of the greenhouse gas.

Corinne Le Quéré at the Max Planck Institute of Biochemistry in Martinsried, Germany and co-workers estimated changes in the Southern Ocean's carbon sink from data taken between 1981 and 2004 at 11 stations in the Southern Ocean and 40 stations worldwide. They calculated the CO₂ flux between the ocean and the atmosphere and estimated the Southern Ocean sink to absorb, on average, between 0.1 and 0.6 gigatonnes of carbon per year. Since 1981, however, the rate of CO₂ uptake slowed by almost 0.2 gigatonnes per year relative to the rate expected given atmospheric CO₂ changes over the same period.

The impaired ability of the Southern Ocean to absorb CO₂ is attributed to increased windiness. This could be a result of atmospheric changes induced by global warming or ozone depletion in the upper atmosphere. Strong winds are predicted to increase this century, suggesting that stabilization of atmospheric CO₂ could be more difficult than expected.