Ice drift in the Weddell Sea in 1990–1991 as tracked by a satellite buoy

Abstract

Ice drift in the Weddell Sea has been studied by using a satellite buoy deployed on an ice floe. The buoy survived for a 20‐month period, indicating a drift trajectory of 10,000 km and yielding 13 months of marine meteorological data. The drift of the ice floe was studied with respect to the winds measured by the buoy. In the central Weddell Sea, the mean drift speed of the ice floe was 0.15 m/s, which was about 3% of the wind speed. More specifically, the drift ratio was 3.4% in the marginal ice zone and 2.4% in the inner pack ice field. On average, the drift was directed 36° left of the wind direction, but the turning angle was larger during the austral summer and smaller during the winter. On time scales of days the drift was primarily wind‐dependent, except for cases during winter periods of high ice concentration and internal ice resistance. For time scales of several months, purely wind‐based simulations of the drift resulted in a discrepancy between the observed and simulated trajectories, but the inclusion of a slow (0.02 m/s) residual current made the simulations significantly better. The geostrophic wind based on European Centre for Medium‐Range Weather Forecasts pressure analyses was estimated for a 1‐month period, and the ice floe was found to drift almost parallel to the geostrophic wind with a speed of 2% of the geostrophic wind speed. Inertial‐type motion superimposed on the wind‐induced drift was found to be a characteristic feature in the marginal ice zone during the austral summer, but it could not be found from the drift in winter when kinetic energy was transferred to larger scales of motion and dissipated into the ice field.