RADAR BACKSCATTER SIGNATURES OF THIN SEA-ICE IN THE CENTRAL ARCTIC

Monitoring the early stages of sea ice growth is vital because the cha nging sea ice cover controls the heat exchange between the ocean and a ir. New ice growth is also responsible for adding brine into the upper portion of the water column. Thin sea ice also significantly affects the albedo of the surface as it changes from a sea surface to an ice s urface. To investigate the ability of radars to map thin ice we perfor med radar backscatter measurements early in the fall freeze-up as part of the International Arctic Ocean Expedition '91 (IAOE'91). We collec ted data over the thin ice types of light nilas, dark nilas, and panca ke/slush ice using a ship-based, C-band FM radar with all four linear polarizations. Our results indicate that radars must be able to measur e sigma0 as low as - 30 dB for W polarization and - 34 dB for HH polar ization. The noise-equivalent sigma0 for the ERS-1 Synthetic-Aperture Radar is - 24 dB and for RADARSAT is - 23 dB. This implies that these sensors are not capable of monitoring thin sea ice types such as dark nilas and grease ice but may be able to detect slightly thicker ice, s uch as light nilas and pancake ice, due to their higher backscatter.