The strength of Southern Ocean overturning circulation ? a process that draws surface waters down to the ocean’s abyss and deep waters up to the surface near Antarctica ? has not been significantly affected by intensifying wind strength over recent decades, a study online in Nature Geoscience reports. A possible future intensification of the wind-driven circulation had been suggested as a mechanism that could inhibit the removal of carbon dioxide from the atmosphere into the deep ocean.

Claus B?ning and colleagues analysed data from the Argo network of floating measurement instruments along with historical oceanographic data from the Southern Ocean. They found that the water in the Antarctic Circumpolar Current has become warmer and less salty over recent decades. From the resulting spatial distribution of water density, they conclude that neither the strength of the Antarctic Circumpolar Current nor of the overturning circulation were affected significantly by the recent strengthening of the westerly winds between 30 and 60? S.

The researchers conclude that the action of small-scale eddies, which are not resolved in most of the earlier ocean models, counteract any wind changes and stabilise the ocean circulation.