Estimation of accumulation area ratio of a glacier from multitemporal satellite images using spectral unmixing

The snowline altitude (SLA) and the accumulation area ratio (AAR) of the Morteratsch glacier, Switzerland are derived using Landsat images over a period of 20 year. To draw the SLA, multitemporal Landsat images are first calibrated to surface reflectance using 6S [1]. A linear spectral unmixing algorithm is applied with accumulation and ablation end-members. Transects best representing the morphology of the glacier are drawn and the SLA is defined using the shifts between the end-member profiles of snow and ice. The results of two mass balance characteristics, SLA and AAR, show that the Morteratsch glacier has changed substantially during the period between 1985 and 2005. The average SLA of the glacier has risen by 131 m and the AAR decreased from 66.2 % to 52.5 % during this period. Comparatively, the eastern part of the Morteratsch glacier has a smaller increase (94 m) in the altitude of the snowline, as compared to that of the western part (183 m).