Monitoring of seasonal glacier mass balance over the European Alps using low-resolution optical satellite images

We explore a new method to retrieve seasonal glacier mass balances (MBs) from lowresolution optical remote sensing. We derive annual winter and summer snow maps of the Alps during 1998–2014 using SPOT/VEGETATION 1 km resolution imagery. We combine these seasonal snow maps with a DEM to calculate a ‘mean regional’ altitude of snow (Z) in a region surrounding a glacier. Then, we compare the interannual variation of Z with the observed winter/summer glacier MB for 55 Alpine glaciers over 1998–2008, our calibration period. We find strong linear relationships in winter (mean R= 0.84) and small errors for the reconstructed winter MB (mean RMSE= 158 mm (w.e.) a). This is lower than errors generally assumed for the glaciological MB measurements (200–400 mm w.e. a). Results for summer MB are also satisfying (mean R and RMSE, respectively, 0.74 and 314 mm w. e. a). Comparison with observed seasonal MB available over 2009–2014 (our evaluation period) for 19 glaciers in winter and 13 in summer shows good agreement in winter (RMSE= 405 mm w.e. a) and slightly larger errors in summer (RMSE= 561 mm w.e. a). These results indicate that our approach might be valuable for remotely determining the seasonal MB of glaciers over large regions.