COMPARISON OF RADAR BACKSCATTER FROM ANTARCTIC AND ARCTIC SEA-ICE

We made backscatter measurements at C band (5.3 GHz) over sea ice in t he Weddell Sea. These measurements were performed from the German rese arch vessel F.S. Polarstem during September and October, 1989. We acqu ired data on First-Year (FY) and Second-Year (FY) snow-covered sea ice at stations where the ship stopped and detailed snow and ice characte rizations were performed. Data were collected at incidence angles from 30 degrees to 75 degrees with all four linear polarizations. The resu lts showed that the presence of slush at the snow-ice interface effect ively masked the distinction between FY and SY ice in the Weddell Sea. Perhaps more importantly, we found that it is possible to distinguish slush-covered and slush-free FY ice flees, depending on incidence ang le. We found that scattering from roughened, slush-free ice was strong er than slush-covered ice at large incidence angles. Essentially the p resence of slush at the snow-ice interface created a new dielectric in terface that was smoother than the original rougher ice surface below. At small incidence angles, quasi-specular reflection from slush-cover ed ice dominated the radar signal. The results further indicated that the volume scattering from the snow and from the ice was small up to 5 0 degrees angle of incidence. We compared the results with data collec ted over sea ice from the Arctic. Backscatter for FY ice in the Arctic and the Weddell Sea were similar in magnitude. Returns from the Arcti c SY ice were about 3-7 dB higher than those from the Weddell Sea SY i ce. We believe that this difference is due to the presence of a slush layer over the SY ice surface studied in the Weddell Sea. The wet slus h layer reduced the penetration depth into the ice, significantly redu cing the volume scatter contribution from the ice.