Summary
Information of sea-ice drift is crucial to understand the East Antarctic climate system, and knowledge of sea-ice dynamics is needed to fully explore the effects of cryospheric changes on the ecosystems within the Antarctic pack-ice zone. Satellite-derived sea-ice data cover the Southern Ocean. They largely reveal broad-scale features in the ice drift and resolve ice motion at multi-daily time intervals. Buoy-derived ice velocities, on the other hand, provide information for limited regions only. However, they contain meso-scale (order of tens of kilometres) and fine-scale as well as high-frequency ice motion. There have been intermittent deployments of drifting buoys off East Antarctica since the mid 1980s, mainly as part of the AAD's research programme. Buoy deployments took place either as part of a coordinated sea-ice experiment, or on opportunistic basis, generally late in the shipping season. Due to the divergent nature of the Antarctic ice pack, buoy survival is often limited to one year or less. Hence buoy-derived data are available only for limited locations and times. Our findings of the East Antarctic sea-ice drift show that the mean ice drift is in response to the major atmospheric circulation systems and, in large, well correlated with topographically forced ocean currents. On the shorter time scales sea-ice dynamics is driven by atmospheric variability as well as by the inertial response and ocean tides. Comparison studies found that satellite-derived ice velocities are about 40% less than those derived from in-situ data. Increased northward sea-ice transport appears to be associated with high atmospheric cyclone intensity during autumn and winter, especially within the Western Pacific sector. Interannual variability in ice drift causes changes in the maximum annual ice extent and affects the seasonal distribution of ice concentration within the pack. This variability gives rise to changes in the sea-ice deformation, and hence in the dynamic contribution to sea-ice thickening, as well as in changed conditions for the resident ecosystems. In addition to a summary of our findings, an outlook on current and proposed initiatives of in-situ sampling of ice motion and related parameters will be presented.