Robin D. Muench
Earth & Space Research, Seattle, Washington.

Laurie Padman
Earth & Space Research, Seattle, Washington.

Susan L. Howard
Earth & Space Research, Seattle, Washington.

E. Fahrbach
Alfred-Wegener Institute, Columbusstrasse, B-2850 Bremerhaven, Germany


Vertical profiles of ocean temperature, salinity, dissolved oxygen concentration and currents were obtained during austral winter 1997 from a region extending from the northeastern Antarctic Peninsula to the South Orkney Plateau in the Weddell Sea. From these data we identify the spatial variation of shear-driven turbulent mixing and estimate the mean diapycnal diffusivity (K_v) in the main pycnocline. We conclude that the mean upper ocean heat flux in the northwestern Weddell Sea is in the range 2-10 W m^-2. The dominant source of oceanic kinetic energy in the region is the ocean tide: tidal current speeds at the shelf break can approach 50 cm s^-1 compared with mean flows of ~5 cm s^-1. We show that the conversion rate of barotropic to baroclinic tidal energy along the South Scotia Ridge, as a pathway for energy flux to the turbulent microscale, is consistent with the data-based estimates of K_v. Baroclinic tides from the ridge irradiate the northern Weddell Sea and may explain observed significant velocity shears in the central Powell Basin, hundreds of kilometers from significant topographic features.