Summary
The 500 km wide swath of the right-looking ERS Wind scatterometer and the orbital geometry allows measurement of the microwave backscatter of all the Antarctic region between latitudes 55°S and 80°S each three days. The values of the backscatter coefficient depend on the incidence angle and look direction of the antenna beams. By removing the contributions to the backscatter of these two effects we derive normalised values of the backscatter coefficient, and from these sythesize a sequence of composite radar images of the surface. The almost continuous operation of the AMI in wind-mode provides a regular series of images commencing in August 1991. Similar propcessing of data from the NSCAT instrument on ADEOS provides a time series of images of that region with a shorter repetition interval. The different wavelength (ku-band) and antenna pattern compared to the ERS C-band scatterometer produces a higher resolution image but this time series is only available for the 9-months from October 1996 to June 1997. The sequences of images clearly show the drift of very large icebergs about Antarctica. The icebergs are identified by the contrast of their brighter backscatter against the relatively darker background of sea ice or open water and the continuity of the feature through a series of images. The largest iceberg observed (B10) has an area of about 8000 sq km which is much larger than the footprint of the scatterometer beams. The smallest iceberg detected has an area estimated at less than 500 sq km, a fraction of the beam footprint area. A combination of various drift tracks shows the continuity of the westward continental-slope current, also known as the Antarctic East Wind Drift, moving anti-clockwise around the continent near to the coast. In several discrete bands of longitude a retroflection can be observed in the current which gives a northwards connection to the southern part of the clockwise Antarctic Circumpolar Current [ACC]. A major