Topography, jets, and eddy mixing in the Southern Ocean

The relation between topography, and the 3D structure of patchy eddy-induced mixing in the Southern Ocean is analyzed descriptively by applying diagnostic methods to output from the Southern Ocean State Estimate. A localized cumulative probability density function method is developed to verify the use of Nakamura's (2001) mixing efficiency in the ocean. Both methods reveal enhanced eddy mixing at mid-depths. The spatial pattern of the mid-depth enhancement of eddy mixing is primarily linked to the merging of multiple jets embedded in the Antarctic Circumpolar Current over topography. We suggest that enhanced eddy mixing over topography is due to locally enhanced baroclinicity and instability within the wake itself, partly due to the convergence of eddies in merging branches of the ACC. Interaction of barotropic and baroclinic eddies may be important to setting the strength and vertical structure of eddy mixing associated with topography.