Changes in Imja Lake and Karda Lake in the Everest Region of Himalaya

Abstract

The Himalaya is a region sensitive to climate change. Changes in the glacial regime are one indicator of global climate changes. There are several studies focusing on analysis of temporal changes of these glacial lakes in the Himalaya re gion. However, the researches on addressing these trends in relation with surrounding topographical conditions are quite limited. In this study, we analyzed spatio-temporal changes in Imja Lake, located on the southern slope, and Karda Lake, located on the northern slope of the Mt. Everest region, in 1976, 1992, 2000, and 2008. Moreover, we examined whe ther the topographic conditions differ between the two slopes. Landsat and ASTER GDEM (advanced space borne ther mal emission and reflection radiometer, global digital elevation model) data were used to identify boundaries of target glacial lakes and to calculate three indices of growth rate compared to year of 1976 (%, GR a ), growth rate compared to preceding year (%, GR b ), and growth speed (m 2 /year, GS ) of the two lakes. The topographic conditions in circular buffer zones from the centroid of the two lakes were analyzed. Although the area of two lakes demonstrated linear in crease from 1976 to 2008, growth rate compared to year of 1976 ( GR a ) differed significantly (Kruskal-Wallis test, p < 0.05). The area of Imja Lake enlarged significantly faster than the one of Karda Lake (Kruskal-Wallis test and Chi squared test for independence on m × n contingency table between 1976, 1992, 2000, and 2008 on g rowth speed ( GS )). The two slopes differed in terms of three topographical variables: altitude, aspect, and angle of inclination (Kruskal- Wallis test, p < 0.05). The differences between the growth trends of the two lakes can be explained by differences in the topographic conditions on their respective slopes. However, differences in temporal changes should be explained by other temporal factors, e.g. climatic variables.