Classification of snow facies on the Greenland ice sheet using passive microwave and SAR imagery

This study uses passive microwave data to monitor climatic trends on the Greenland ice sheet by observing changes in the snow facies or zones. Since the snow facies are a result of climatic differences on the ice sheet, they could be indicators of climate change. Special Sensor Microwave/Imager (SSM/I) data are used to classify the ice sheet into the dry snow, percolation, wet snow and ice zones. Signature pixels representing these zones are selected based on synthetic aperture radar (SAR) imagery. A scatterplot of the cross polarization gradient ratio (XPGR) vs. the polarization ratio (PR) for signature pixels representing the four zones results in separate clusters. The snow facies are delineated using these clusters in a maximum likelihood classification (MLC) scheme. Using these signature statistics, the ice sheet is classified for all years of SSM/I data (1987-1996). The authors observe that the ice sheet shows a slight warming trend from 1987 to 1991, followed by a sudden cooling, which may be attributed to the eruption of Mt. Pinatubo. Since then the decreasing area of the dry snow facies suggests an overall warming trend.