Study of temporal changes in snout position and wet snow line for Gangotri glacier using remote sensing, ground observations and meteorological data

The temporal changes (1891-2010) in snout position of Gangotri glacier were monitored using Landsat images, ground observations and SoI (Survey of India) toposheets. Temporal changes (2001-09) in wet snow line (wsl) altitude were also observed using LISS-III images and high resolution (6 m pixel size) DEM generated using Cartosat stereopair. These observations were correlated and justified with available snow meteorological data. OCGM (Oerlemans Coarse Grained Model) was run in parallel using meteorological inputs to support the obtained glacier retreat using Landsat data during 2001-10. The retreats observed were 73 m and 54 m respectively using Landsat data and OCGM. The difference was less than 20 m (less than a pixel of Landsat image) thus supporting the usefulness of remote sensing observations for monitoring of rough and hard to access terrain. The wsl altitude showed an overall ascending trend during melting season (May to September). Some atypical fluctuations in this trend were observed for different years which could be explained using available meteorological records.