Hypsometric analysis of major glaciers of Shigar river basin in the Karakoram mountain range

Abstract

Unique environment and multifaceted mountain geo-dynamics of Karakoram disguise the variations present in the hypsometries (frequency distribution of altitudes). We report hypsometry of mountain glaciers of Shigar river basin (with a 7046 km² land-covered area) in the Karakoram, to understand area-elevation relations of glacier environments and effects of magnitude of glaciated-area and location of Equilibrium Line Altitude (ELA). We apply a method based on histogram analysis of glacier hypsometry and a pixel-based regression tool on an updated version of glacier outlines. A big portion of the largest glaciated area (20.63%) of Shiger river basin lies between mixed (high velocity), net accumulation (low velocity) regime of horizontal zone and clean-dusty regime of vertical zone. The smallest glaciated area is found in the extreme ends of the high (in the net avalanche accumulation and low velocity zone and temperature below -18° C) and low (the mostly debris and clean dust-covered ice, net ablation and medium velocity area) altitudes. There are major differences in the hypsometry of the smallest and largest glaciers like except Panmah glacier, large portions of largest glaciers (e.g. Baltoro, Biafo and Chogo Lungma) lies at ELA. Smallest glaciated area lies in low altitudes may contribute melt-water significantly to Indus river rise due to their shorter response times as compared to larger glaciers. The high elevation precipitation may sustain the glaciers of this basin whose melt-waters, especially those from largest glaciers, in turn feed the Shigar river. This dependence of the river on glacial and ice melt is manifested in the huge seasonal variation in its flow.