Changes in the strength of the winds that circle Antarctica lead to changes in the depth of the mixed surface layer of the Southern Ocean, concludes a study online this week in Nature Geoscience.
The mixed surface ocean is a crucial link between the atmosphere and the deeper layers of the ocean, and its depth can affect air-sea exchange, carbon and heat storage in the ocean, as well as biological productivity.
Jean-Baptiste Sallee and colleagues analysed temperature and salinity measurements to show that an intensification in the wind system that circles around the South Pole leads to deeper mixed layers in the eastern Indian and central Pacific oceans. By contrast, in the western parts of these ocean basins, the surface mixed layer becomes shallower. The researchers suggest that this asymmetry can be explained by small deviations from the circular wind patterns, and their effect on the heat flux between ocean and atmosphere.
In an accompanying News & Views, Sarah Gille says "Sallee and colleagues provide important ground truth for assessing the sensitivity of the depth of the Southern Ocean's mixed layer to climate change."