WINTER SEA-ICE MAPPING FROM MULTIPARAMETER SYNTHETIC-APERTURE RADAR DATA

The limitations of current and immediate future single-frequency, sing le-polarization, space-borne SARs for winter sea-ice mapping are quant itatively examined, and improvements are suggested by combining freque ncies and polarizations. Ice-type maps are generated using multi-chann el, air-borne SAR observations of winter sea ice in the Beaufort Sea t o identify six ice conditions: (1) multi-year sea ice; (2) compressed first-year ice; (3) first-year rubble and ridges; (4) first-year rough ice; (5) first-year smooth ice; and (6) first-year thin ice. At a sin gle polarization, C- (lambda = 5.6 cm) and L- (lambda = 24 cm) band fr equencies yield a classification accuracy of 67 and 71%, because C-ban d confuses multi-year ice and compressed, rough, thick first-year ice surrounding multi-year ice floes, and L-band confuses multi-year ice a nd deformed first-year ice. Combining C- and L-band improves classific ation accuracy by 20%. Adding a second polarization at one frequency o nly improves classification accuracy by 10-14% and separates thin ice and calm open water. Under similar winter-ice conditions, ERS-1 (C(VV) ) and Radarsat (C(HH)) would overestimate the multi-year ice fraction by 15% but correctly may the spatial variability of ice thickness; J-E RS-1 (L(HH)) would perform poorly; and J-ERS-1 combined with ERS-1 or Radarsat would yield reliable estimates of the old, thick, first-year and thin-ice fractions, and of the spatial distribution of ridges. Wit h two polarizations, future single-frequency space-borne SARs could im prove our current capability to discriminate thinner ice types.