Compatibility of sea ice edges detected in ERS-SAR images and SSM/I data

The determination of an ice covered ocean surface from ERS-SAR images is not directly possible if the values of the normalized radar cross section are similar for open water and sea ice. SAR imagery of ocean surface waves can be used to detect the ice coverage in such cases. Sea ice changes directly the wave dynamics and has an impact on the nonlinear imaging of ocean waves by SAR. The energy distribution of the SAR image spectrum of a wave system propagating in sea ice deviates characteristically from the energy distribution of the same wave system propagating in open water. In this study parameters have been derived from the second moments of SAR image spectra, which are suitable to describe this effect quantitatively. These parameters are used to define an ice edge. Results of this analysis are compared with ice concentration isolines derived from SSM/I data using the NASA Team algorithm, and with a high resolving ice edge detection algorithm based on the 85 GHz channels of the SSM/I. Ice edges detected in ERS-SAR images agree well with the 30% ice concentration isolines of the NASA Team algorithm. The ice edge detection algorithm for the SSM/I data is in good agreement with the SAR ice edge.