Climate Change Impact on Glaciers in the Langtang and Imja Sub-basins of Nepal from Late 70s to 2010

Abstract:

Increase in glacier number and decrease in glacier area are perceived significantly in recent decades in Nepal. The observed glacier changes are one of the key indicators of climate change. In order to understand the impact of climate change on glaciers a repeat decadal glacier inventory since 1980s based on landsat images were carried out in the Langtang and Imja valleys. The recent glacier outlines were delineated semi-automatically from the images using object based image classification (obic) in Definien Developer. The glacier outlines of other decades were obtained by manual editing on the glacier polygons of semi-automatically derived glaciers polygons by overlaying separately on the images of respective years. The result shows that the glacier area has been decreased by 26% in Langtang valley in the period 1976-2009 and 28% in Imja valley in the period 1979-2010. The lowest elevation of glaciers has been shifted upward by 50m and 115m in Imja and Langtang valley respectively. The annual mean temperature from 1988 to 2008 were found to be 4.2^oC and 0.3^oC in Langtang valley and Imja valley respectively. The rate of temperature rise in this period was 0.116^oC yr^-1 and 0.09 ^oC yr^-1 in Langtang valley and Imja valley respectively. The rise of mean decadal and annual mean temperature in Langtang and Imja valleys are one of the key factors of shrinking and retreating of glaciers.