Turbulent Mixing in the Depths of the Southern Ocean is Impacted by the Surface

The Southern Ocean can impact both global ocean circulation and the world's climate. Now, scientists have learned a bit more about these waters and have found that turbulent mixing in the deep varies with the strength of surface eddies--the ocean equivalent of storms in the atmosphere.

The Southern Ocean plays an important role when it comes to the global overturning cycle. This cycle is a system of surface and deep ocean currents that link all oceans. Because these currents transport warm and cold water, they play a huge role when it comes to the Earth's climate; they influence which land masses are exposed to cold or warm temperatures. Because the Southern Ocean around Antarctica is the only location where the ocean can circulate freely all the way around the globe without continental barriers, it's a huge part of the ocean cycle.

The ocean itself isn't just one mass. Instead, it's made up of layers-rather like a cake. These layers consist of different "flavors" that depend on temperature and salinity. Water moves easily along horizontal, also known as isopycnal, layers, but mixes very slowly across the layers, known as diapycnal mixing. This mixing combination, both diapycnal and isopycnal, drives the upwelling of deep waters to the surface.

In order to learn a bit more about this mixing, the researchers took measurements of small-scale temperature and velocity fluctuations in the Southern Ocean. In the end, they found that turbulence in deep water significantly correlated with surface eddy activity. These surface eddies, in turn, are probably caused by westerly winds over the Southern Ocean.

"These findings will help us to understand the processes that drive the ocean circulation and mixing so that we can better predict how our Earth system will respond to the increased levels of carbon dioxide that we have released into the atmosphere," said Katy Sheen, one of the researchers, in a news release.

The findings are published in the journal Nature Geoscience.