WEDDELL SEA-ICE DRIFT - KINEMATICS AND WIND FORCING

Ice drift in the Weddell Sea was studied on the basis of positional an d meteorological data from Argos buoys drifting in 1990-1992 and surfa ce pressure analyses from the European Centre for Medium Range Weather Forecasts (ECMWF). The drift kinematics showed differences between th e eastern and western parts of the Weddell Sea. Close to the Antarctic Peninsula, the ice drifted as an almost nonrotating uniform field at a low speed, having reduced small-scale motions with little meandering , compared to regions further to the east. Inertial motion was detecte d from the ice drift in areas east of 35 degrees W and in the region o f the Antarctic Circumpolar Current. On timescales of days, wind was t he primary forcing factor for the drift. A linear model between the wi nd and ice drift explained 40-80% of the drift velocity variance. The degree of explanation was higher in the central Weddell Sea (around 40 degrees W) and lower closer to the Antarctic Peninsula. The geostroph ic wind was found to provide almost as good a basis for the general dr ift estimation as the surface wind observed by the buoys, although str ong cyclones were not well detected by the ECMWF analyses. The data su ggest a dependency upon atmospheric stability such that stable stratif ication reduces the wind forcing on the drift. For 60-80% of the time the direction of the drift deviated less than 45 degrees from the geos trophic wind and for 45-70% of the time less than 45 degrees from the ocean current. Ice transport through a transect crossing the Weddell S ea from the Antarctic Peninsula tip to Kapp Norwegia was estimated on the basis of the geostrophic winds, the drift's observed response to t he wind, and literature-based information on ice concentration and thi ckness. The estimated annual mean net export in 1992-1994 varied from 8000 to 22,000 m(3)/s. Most of the net export took place in winter and spring, export prevailing west of 35 degrees W and import east of it.