SAR measurements of directional wave spectra in viscous sea ice

A procedure aimed at the estimation of the directional wave spectrum propagating in grease ice composed of frazil and pancakes from SAR images is discussed. The procedure assumes the wave field is coming from the ice-free region and can track its spectral changes while it propagates inside the ice field. According to the assumption of continuum medium, physical ice properties can then be retrieved using a recently developed wave propagation model in sea ice. The model represents both the ice layer and the water beneath it as a system of viscous fluids. As a result, the wave dispersion and the energy attenuation rate are related to sea ice concentration and thickness. An ERS-2 SAR scene gathered in the Odden ice tongue developed in the Greenland Sea during 1997 is considered as case study. The scene includes open sea and ice covered waters where a wave field is traveling from the open sea region. The resulting wave field in sea ice is tracked, thus allowing the estimation of the wave changes as a function of the ice parameters. Results are finally compared with external ice measurements.