Satellite tracking of icebergs in the Weddell Sea

Small to medium sized icebergs (200 m to 10 km across) in two areas of the Weddell Sea were tracked using satellite-borne Synthetic Aperture Radar (SAR) from 22 January-21 February 1994 and 29 January-25 February 1992 respectively. The westward mass flux of icebergs in the Antarctic Coastal Current was estimated at the eastern entrance to the Weddell Sea as being 50-70 Gta(-1). A large contrast was found between observations over the narrow shelf here and the off-shelf area. The latter region had very much reduced iceberg density, and the bergs moved with slower and less coherent velocities compared with the fast, but narrow (10-20 km wide) flow in the Coastal Current. This region is a promising site for the monitoring of decadal trends in iceberg fluxes. The second study area in the south-western Weddell Sea showed iceberg motion consistent with non-Contemporaneous observations of tagged icebergs, with steady flow parallel to the shelf-ice edge, at significantly lower densities and speeds than in the Coastal Current but almost double that observed off-shelf in the eastern Weddell Sea. We also suggest that shipboard observations of icebergs need careful analysis to avoid their over-estimating true iceberg concentrations by a substantial amount.