Comparison of sea ice signatures in OKEAN and RADARSAT radar images for the northeastern Barents Sea

Sea ice signatures in near-simultaneous OKEAN real aperture radar (RAR) and RADARSAT synthetic aperture radar (ScanSAR) images have been analyzed and compared for the northeastern part of the Barents Sea in April 1998. Signatures of major sea ice types and features in these images have been identified and verified by in situ observations on board the nuclear icebreaker Sovetsky Soyuz. It is shown that both RAR and ScanSAR images can be used for detection of new, young, first year, and multiyear sea ice types, multiyear and fast ice boundaries, flaw polynyas, wide fractures, giant and vast ice floes, and large areas of rough ice. Backscatter signatures of the major sea ice types are analyzed and compared, and the backscatterina differences between the ice types are estimated for both types of data. High-resolution ScanSAR images are found to be particularly suited for discrimination of narrow leads and level areas in compact sea ice. A study of the radar signatures of a flaw polynya to the north of Cape Zhelaniya was conducted using ERS SAR, RADARSAT ScanSAR, and OKEAN RAR over a period of 33 h. The backscatter from the polynya varied significantly between VV and HH polarization and as a consequence of changing physical properties due to freezing during the 33 h period. Access to satellite radar data for use in sea ice research will increase in the near future. Wide-swath SAR data are available from both RADARSAT and ENVISAT from 2003, and a new RAR satellite, SICH-M1, is planned for launch in 2004.