Fast-ice distribution in East Antarctica during 1997 and 1999 determined using RADARSAT data

We present the first detailed maps of fast ice around East Antarctica (75 degrees E-170 degrees E), using an image correlation technique applied to RADARSAT ScanSAR images from November in 1997 and 1999. This method is based upon searching for, and distinguishing, correlated regions of the ice-covered ocean which remain stationary, in contrast to adjacent moving pack ice. Within the overlapping longitudinal range of similar to 86 degrees E-150.6 degrees E, the total fast-ice area is 141,450 km(2) in 1997 and 152,216 km(2) in 1999. Calibrated radar backscatter data are also used to determine the distribution of two fast-ice classes based on their surface roughness characteristics. These are "smooth" fast ice (-25.4 dB to-13.5 dB) and "rough" fast ice (-13.5 dB to-2.5 dB). The former comprises similar to 67% of the total area, with rough fast ice making up the remaining similar to 33%. An estimate is made of fast-ice volume, on the basis of fast-ice type as a proxy measure of ice thickness and area. Results suggest that although fast ice forms 2-16% of the total November sea ice area for this sector of East Antarctica in 1997 and 1999 (average 8.3% across maps), it may comprise 6-57% of the total ice volume (average similar to 28% across maps). Grounded icebergs play a key role in fast-ice distribution in all regions apart from 150 degrees E-170 degrees E. These are "snapshot" estimates only, and more work is required to determine longer-term spatiotemporal variability.