Passive microwave signatures of autumnal sea ice types from ship-based observation

Surface-scale passive microwave signatures of newly formed sea ice were collected using ship-based radiometers in the Southern Beaufort Sea and Amundsen Gulf between mid October and mid November 2003. Sea ice in the region was highly spatially and temporally variable. Over a heterogeneous area of open water and thin ice, polarization ratios showed multimodal frequency distributions and the differences between surface and satellite radiometric data were large. However, differences were small over a homogeneous area of snow-covered first-year ice during late fall and the corresponding histograms showed unimodal distributions. Our results suggest that sub- pixel heterogeneity is a critical factor in characterizing the mixture rules used in passive microwave sea ice algorithms.