Mechanisms of eddy dissipation in the Southern Ocean
Mesoscale eddies are known to play an essential role in the dynamics of the Southern Ocean and modulate its response to changing forcing. However, relatively little is known about the processes that dissipate eddy energy. Results from an analysis of in-situ observations in the Drake Passage are presented that relate to two potentially important mechanisms of eddy dissipation. 1) Autonomous profiling floats passing over the Shackleton Fracture Zone detected a large lee wave event, which is characterised in terms of energy fluxes and turbulent dissipation. 2) The interaction of eddies and internal waves away from boundaries is analysed using data from a mooring array, and quantified as an energy flux from eddies to waves. These observations provide the first unambiguous evidence of a lee wave event in the Southern Ocean. Furthermore, they suggest that the magnitude of dissipation caused by eddy – wave interactions is similar to that of other possible mechanisms such as lee wave generation and bottom boundary layer drag.