Use of ocean wave imaging to detect the marginal ice zone in ERS-SAR images

The discrimination between open water and sea ice in the marginal ice zone (MIZ) imaged by ERS-SAR is often not unique, especially if it is carried out by using only the normalized radar cross section (NRCS). SAR imaging of ocean surface waves traveling into the MIZ offers the possibility to detect the transition from open water to sea ice. Sea ice changes the dynamics of an ocean wave system and the azimuthal low pass filtering of the non-linear imaging by SAR. Both effects are clearly visible in SAR image spectra from which three parameters have been derived describing quantitatively the distribution of spectral energy in wavenumber space. A change of the parameters reveals the presence of an ice cover on the ocean surface. These parameters serve for the definition of an ice edge within the MIZ in the sense of an outer border of the influence of sea ice on ocean wave imaging by SAR.