Eddy/tidal mixing and transport at the Antarctic margins

Ocean processes occurring along the Antarctic continental slope admit shoreward transport of heat toward the continent's marine-terminating glaciers and export newly-formed dense waters from the continental shelf. Recent modeling studies indicate that both eddies and tides may modulate these processes in all sectors of the Antarctic margins. However, due the computational cost of resolving the small (~20km) scales of Antarctic shelf/slope eddies, previous analyses have been limited to regional models and idealized process studies. In this study we investigate eddy/tidal transport and dynamics around the entire Antarctic shelf break using output from recent global ECCO2 simulations run at 1/24th and 1/48th degree horizontal resolutions. We use energy and vorticity budgets to characterize the eddy/tidal-mean flow interaction in the Antarctic Slope Current (ASC). We show that tidal forcing produces a distinct dynamical regime arises in which the core of the ASC flows at almost exactly the same speed as the overlying sea ice, resulting vanishing surface momentum and energy forcing that is accommodated by lateral momentum and energy fluxes. Eddies generated by baroclinic instabilities in this steep slope front effect shoreward heat transport across the continental slope, particularly where the continental shelf break is interrupted by troughs in the ocean bed. We also discuss how this dynamical regime varies between different sectors of Antarctica.