Dissipation of geostrophic eddy energy in the Southern Ocean

Abstract: 

Mesoscale eddies are the most energetic motions in the ocean, but the fate of their energy in the ocean remains poorly understood. Eddy generation in the Southern Ocean tends to be enhanced near prominent topographic features, creating localised hot spots of eddy stirring and turbulent mixing. In this study, realistic internal wave-permitting simulations of one of the hot spots, the Macquarie Ridge region of the Southern Ocean, are used to investigate the energy dissipation of the Antarctic Circumpolar Current fronts and eddies. The simulations are initialised and forced at open boundaries by the outputs from the Southern Ocean State Estimation (SOSE) and carried out for several years for a range of resolutions from the eddy-resolving, about 10 km, down to the submeso-scale resolving and internal wave-permitting, ~1.6km, horizontal resolution. The total mechanical energy budget, including inflow and outflow of kinetic energy across the boundaries, surface wind power input and energy dissipation by bottom drag and interior viscous friction, is diagnosed and closed within 5-10%. The distribution of the viscous energy dissipation throughout the ocean and the relative contribution of the surface and deep ocean processes to the energy dissipation is quantified and discussed.