SAR glacier facies classification and firn line as a climate change indicator on Svartisen glacier, Northern Norway

摘要

The position of the firn line of Svartisen has been determined using ERS-2 SAR data from 1995 till 2003. The firn line is detected by first correcting the image backscatter intensity for topographic and geometric contributions using the Muhlemann backscat-tering model. We have also developed a method for monitoring changes in glacier facies. We discriminate between firn and ice facies based on the backscatter intensity since frozen firn has a much higher backscatter than ice. Transects across different areas of the glacier were chosen based on requirements of smoothness of topography, existence of precipitation zones, as well as the availability of field data for validation and comparison Following the stable conditions of the nineteen nineties we have observed a substantial retreat of the firn line over the last few years, The equilibrium line derived from field measurements shows a similar trend as the firn line changes, but it has larger year-to-year variability. This indicates that the firn line altitude changes due to the smaller variance may be a better indicator of climate change than the equilibrium line.