SOME IMPLICATIONS OF EKMAN LAYER DYNAMICS FOR CROSS SHELF EXCHANGE IN THE AMUNDSEN SEA

Abstract

Exchange of seawater across the continental shelves off West Antarctica strongly influences the available oceanic heat that leads to subsurface glacial melting at the interface between the ocean and the continental West Antarctic Ice Sheet. One mechanism that contributes to the cross-shelf transport is Ekman transport induced by along-slope currents over the slope and shelf break. Previous studies show that Ekman layers in a stratified environment tend to become arrested. When the Ekman transport moves relatively dense water up the slope a pressure gradient is created acting to move the dense water back down. This (baroclinic) pressure gradient is oppositely directed to the (barotropic) pressure gradient that drives the primary along-slope current, and when they become equal in magnitude they cancel out and the Ekman layers are said to be arrested. An investigation of this process is applied to the Amundsen Sea shelf break region, using recently acquired and historical field data to guide the analyses. During a winter 2008-09 cruise, along-slope currents were observed at transects across the eastern and western reaches of the Amundsen slope. Currents in the east, near 110°W, flowed eastward and appeared to be associated with the Antarctic Circumpolar Current (ACC).eet. One mechanism that contributes to the cross-shelf transport is Ekman transport induced by along-slope currents over the slope and shelf break. Previous studies show that Ekman layers in a stratified environment tend to become arrested. When the Ekman transport moves relatively dense water up the slope a pressure gradient is reated acting to move the dense water back down. This (baroclinic) pressure gradient is oppositely directed to the (barotropic) pressure gradient that drives the primary along-slope current, and when they become equal in magnitude they cancel out and the Ekman layers are said to be arrested. An investigation of this process is applied to th