The annual coastal erosion rates of Arctic coasts are among the highest in the world, and the rates are increasing because of climate change. Monitoring of these mass movements with optical images is challenging due to frequent cloud cover of the Arctic. Synthetic Aperture Radars (SAR) are barely affected by the atmosphere, but the commonly used interferometry methods are not effective for the rapidly changing Arctic coastline. Therefore researchers introduced a backscatter-threshold based

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... d with high-resolution TerraSAR-X images. The aim of this study was to advance SAR data analysis for coastal erosion measurements. Therefore, this study applies threshold classification to a variety of Arctic SAR images. TerraSAR-X X-band, PALSAR and PALSAR-2 L-band, and Sentinel-1 C-band ellipsoid corrected images were analyzed. The images had spatial resolutions of 0.62 to 20 m and various polarizations. The thresholds were tested with and without filtering in study areas along the Yukon Coast, the Bykovsky Peninsula, and the Barents Sea Coast. The analysis showed only weak effects of the incidence angle on the backscatter. All sample distributions were modeled well with linear threshold functions. During the error assessment all steep coast test samples were classified correctly by the threshold functions (100% producer's accuracy). Misclassification of land and water occurred for all threshold functions. Overall, the threshold functions for filtered, co-polarized images had a slightly higher classification accuracy, with Kappa Coefficients between 83.52% and 99.84%. Misclassifications were mainly caused by wet snow, wide sand beaches, and infrastructure. The classification results were further used to calculate seasonal, annual, and multi-year coastline change rates. The coastline was identified based on steep cliff classifications or the border between water and land classifications. For regions near Kay Point on the Yukon Coast, the near-zero calculated seasonal and annual shoreline change rates matched optical indic [...]