Calibrated Ers-1 Sar Signatures and Video Underlights Over Artic Ice

Radar backscatter signatures of Arctit ice during advanced melt and freeze-up conditions are presented. The backscatter coefficients were determined from ERS-1 SAR images, and the different ice types were classified based on helicopter video and field observations. During advanced melt only two main classes were observed: old ice and open water leads. The contrast between the two classes is dependent on the wind speed and direction, but in the studied case open water appeared brighter than the ice. The open water signature differed from empirical ocean backscatter models suggesting that the wave spectrum is different in wind-roughened leads as compared with the open ocean. During freeze up, new ice, nilas and young ice were also encountered. These ice types showed a less stable backscatter signature, probably due to the variable characteristics of frost flowers, saline snow, frazil ice, and deformation features which were observed. The old and young ice showed little contrast or even ambiguous backscattering coefficients, implying that texture, context and temporal changes will be important for a correct classification.