Assessment of recent glacier changes and its controlling factors from 1976 to 2011 in Baspa basin, western Himalaya

Abstract

Himalayan glaciers are normally difficult to monitor through field observations because of highly rugged and extremely inaccessible mountainous terrain. Thus, using Landsat data (MSS, ETM+ and TM), changes in glacier area, length, and debris cover have been delineated in the Baspa basin, which is a highly glacierized sub-basin of the Satluj River in the western Himalaya. Out of the total 109 glaciers inventoried through Landsat TM imagery (2011), 36 glaciers were found to be heavily debris covered (32.5 ± 2.0%). A shrinkage in glacier area of 41.2 ± 10.5 km2 (i.e., 18.1 ± 4.1%) at a rate of 1.18 ± 0.3 km2 a–1 from 1976 (227.4 ± 9.4 km2) to 2011 (186.2 ± 3.7 km2) has been recorded. The overall glacier retreat studied for 33 glaciers varied from 3.3 ± 0.03%, that is, 0.87 ± 0.06 km at a rate of 17.2 ± 1 m a–1 to 30 ± 6.6%, that is, 0.60 ± 0.04 km at a rate of 24.8 ± 0.2 m a–1. Consequently, the debris cover has increased by 23.5 ± 1.4 km2 (16.3 ± 3.8%) from 1976 to 2011. Overall, the clean, small sized, low-altitude glaciers with south to southwest aspect and relatively steep slope have lost maximum area, which indicated a major control of these factors on the glacier changes. Simultaneously, a trend estimation of observed climatic data (1976/1985–2008) of three meteorological stations (Sangla, Rakcham, and Chitkul) using Mann Kendall test, Sen’s Slope estimator and linear regression test revealed an increase in temperature and rainfall while a decline in snowfall. Importantly, the Tmin has increased significantly at 95% confidence level during all the studied periods. The mean annual Tmin and Tmax indicated a rising trend at a rate of 0.076 and 0.071 °C a–1. Thus, the changes in temperature and precipitation may be the major causes of accelerating the glacier ablation. The higher area changes (53.0 ± 0.4%), of small glaciers <0.5 km2 mark their sensitivity to climatic changes especially rising temperature. Under the warming climate, formation and progressive expansion of glacial lakes is expected because of the glacier recession in the basin. For instance, the Baspa Bamak Proglacial Lake at the snout of Baspa Bamak glacier has expanded continuously from 2000 onward.