FUSION OF SATELLITE ACTIVE AND PASSIVE MICROWAVE DATA FOR SEA-ICE TYPE CONCENTRATION ESTIMATES

Young first-year sea ice is nearly as important as open water in modul ating heat flux between the ocean and atmosphere in the Arctic, Just a fter the onset of freeze-up, first-year ice is in the early stages of growth and will consist of young first-year and thin ice. The distribu tion of sea ice in this thickness range impacts heat transfer in the A rctic. Therefore, improving the estimates of ice concentrations in thi s thickness range is significant, NASA Team Algorithm (NTA) for passiv e microwave data inaccurately classifies sea ice during the melt and f reeze-up seasons because it misclassifies multiyear ice as first-year ice. We developed a hybrid fusion technique for incorporating multiyea r ice information derived from synthetic aperture radar (SAR) images i nto a passive microwave algorithm to improve ice type concentration es timates, First, we classified SAW images using a dynamic thresholding technique and estimated the multiyear ice concentration. Then we used the SAR-derived multiyear ice concentration to constrain the NTA and o btained an improved first-year ice concentration estimate, We computed multiyear and first-year Ice concentration estimates over a region in the eastern-central Arctic in which field observations of ice and in situ radar backscatter measurements were performed. with the NTA alone , the first-year ice concentration in our study area varied between 0. 11 and 0.40, while the multiyear Ice concentration varied from 0.63 to 0.39, with the hybrid fusion technique, the first-year Ice concentrat ion varied between 0.08 and 0.23 and the multiyear ice concentration w as between 0.62 and 0.66. The fused estimates of first-year and multiy ear ice concentration appear to be more accurate than NTA, based on ic e observations that were logged aboard the U.S. Coast Guard icebreaker Polar Star in the study area during 1991.