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.
