Wave spectra of SAR imagery of the Odden ice tongue

SAR imagery from the ERS-1 satellite provides an excellent tool for continuous observation of sea-ice in polar regions. On the basis of a theoretical model, wave spectra derived from SAR images can be used to detect ice thickness in the Marginal Ice Zone if the ice is composed of frazil or pancake. A field experiment involving several scientific institutions was performed in the Odden ice tongue in the Greenland Sea during April 1993. A set of 24 high-resolution SAR images for the same period and covering the same area was acquired and processed. The image analysis consisted of the following steps: (1) geo-location and geo-reference of each image onto a UTM map projection; (2) mosaicking, after compression, of all images onto a general map of the Odden; (3) extraction of full resolution windows, 512/spl times/512 pixel size, outside (open sea) and inside the ice cover in the image; (4) wave spectra computation by means of the Optical Fourier Transform; (5) contour plot and peak detection of wave spectra. The analysis gives the change of wavelength and angle of refraction of the dominant wave entering the ice field. Ice thickness values derived from the theory were larger than those measured during the field experiment. This finding suggests a need to refine the dispersion relation in the theoretical model.