Antarctic sea-ice velocity as derived from SSM/I imagery

Sea-ice velocities derived from remotely sensed microwave imagery of the Special Sensor Microwave/Imager (SSM/I) have been analyzed for changes over time in Antarctic sea-ice velocity, for the period 1988–2004. Year-to-year variability in mean Antarctic annual SSM/I-derived ice speed is small (17 year standard deviation (SD) 1⁄4 0.008m s), with greater interannual variability in the zonal (eastward positive) velocity components (17 year SD 1⁄4 0.016m s). Seasonally, minimum ice speed is encountered during summer, when nearly all Antarctic sea ice is within the marginal ice zone. Ice motion peaks during winter and spring, due to high velocities encountered in the outer pack of the seasonal sea-ice zone. The correlation (R 1⁄4 0.47) between winter Southern Annular Mode (SAM) and mean winter ice speed highlights the importance of atmospheric forcing on sea-ice dynamics. The spatial pattern of the correlation of the standardized SAM index with the June–November ice speed exhibits a wave-3 pattern, which matches the sea-level pressure distribution. Sea-ice speed in the upstream regions of quasi-stationary centres of low sea-level pressure is likely to increase (decrease) during high (low) SAMyears, and the opposite for sea-ice speed in the downstream regions of the centres.