Observations of Dissipation and Mixing over the Amundsen Sea Continental Shelf

Over one hundred thirty profiles of velocity and temperature microstructure collected in the Amundsen Sea in February-March 2014 are analysed to estimate energy dissipation and mixing rates over the continental slope and shelf. Generally low levels of dissipation, of 10^-10 to 10^-9 W/kg, are observed below the surface layer, including around the boundary between Circumpolar Deep Water (CDW) and the overlying colder Winter Water (WW); however, temperature diffusivities show a slight elevation near this level over the outer and middle shelf. Occurrences of elevated mid-column and near-bottom dissipation are described and their relationship to bottom topography and finestructure observed by coincident conductivity-temperature-depth (CTD) and lowered acoustic Doppler current profiler (LADCP) casts is investigated. The implications for oceanic heat delivery to the Amundsen Sea ice shelves are discussed.