Resolving Biases in DEM Differencing for Estimation of Change in Elevation of Glacier Surfaces Using Cartosat-I Stereo Data

Abstract

Understanding the impact of climatic variations on Himalayan-Karakoram glaciers has now become a necessity for planning water resources of Indus-Ganga–Brahmaputra basins. One of the most important parameters to assess this is the mass balance of glaciers. Besides ground-based studies of mass balance, differencing of Digital Elevation Models (DEMs) is now commonly employed for estimating the long-term changes for this purpose. Before applying this approach, it is necessary to evaluate the accuracy of elevation changes of glacier surfaces with respect to terrain parameters and the DEMs used. This study demonstrates the factors governing DEM differencing using an example of four glaciers of Zanskar region by comparing DEMs extracted from Cartosat-1 stereo data of ablation season of the years 2005 and 2015. A strong relation has been observed between slope of the terrain and elevation changes between the two DEMs on non-glaciated stable terrain (R2 = 0.8144). The regression equation thus developed has been used to correct elevation changes on glacier surface. Lowering of ablation zone of the four sample glaciers over a period of ten years has been of the order of 3.92, 11.17, 4.99 and 4.39 m. The results obtained by using Cartosat-I DEMs have also been validated using ASTER DEMs of similar time interval.