Mapping the snow line altitude for large glacier samples from multitemporal Landsat imagery

The cryosphere of mountain regions is highly sensitive to climate change. This is particularly evident in region wide retreat of glaciers and reduced snow coverage in mountain areas. Snow cover is an important parameter in the glacier mass but also energy balance as it controls the energy fluxes on the glaciers surface and protects the glacier from melt. Monitoring snow cover and the snow line altitude of a glacier through remote sensing data near the end of the ablation season may be considered roughly representative for the equilibrium line altitude on Alpine glaciers which is a useful indicator of the annual mass balance. The aim of this study is to develop an automated tool to retrieve information related to glacier mass balance based on multitemporal satellite imagery and an already existing glacier inventory. The method is developed in the Ötztal Alps where reliable in-situ data are available for several glaciers for a period longer than 30 years. The results show a clear rise of the snow line altitude, which is in agreement with the equilibrium line altitude observed in the field. Nevertheless, the retrieved snow lines by remote sensing imagery are generally too low (> 200 m difference). Part of this underestimate is likely due to the mapping method or the usage of a present DEM which is not representative for historical snow line altitudes. After a proper validation of the current methodology, it can subsequently transferred to other regions in the world.