Abstract
Abstract. This study investigates spatial patterns in glacier characteristics and area changes at decadal scales in the eastern Himalaya – Nepal (Arun and Tamor basins), India (Teesta basin in Sikkim) and parts of China and Bhutan – based on various satellite imagery: Corona KH4 imagery, Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Advanced Spaceborne Thermal Emission Radiometer (ASTER), QuickBird (QB) and WorldView-2 (WV2). We compare and contrast glacier surface area changes over the period of 1962–2000/2006 and their dependency on glacier topography (elevation, slope, aspect, percent debris cover) and climate (solar radiation, precipitation) on the eastern side of the topographic barrier (Sikkim) versus the western side (Nepal). Glacier mapping from 2000 Landsat ASTER yielded 1463 ± 88 km2 total glacierized area, of which 569 ± 34 km2 was located in Sikkim and 488 ± 29 km2 in eastern Nepal. Supraglacial debris covered 11% of the total glacierized area, and supraglacial lakes covered about 5.8% of the debris-covered glacier area alone. Glacier area loss (1962 to 2000) was 0.50 ± 0.2% yr−1, with little difference between Nepal (0.53 ± 0.2% yr−1) and Sikkim (0.44 ± 0.2% yr−1. Glacier area change was controlled mostly by glacier area, elevation, altitudinal range and, to a smaller extent, slope and aspect. In the Kanchenjunga–Sikkim area, we estimated a glacier area loss of 0.23 ± 0.08% yr−1 from 1962 to 2006 based on high-resolution imagery. On a glacier-by-glacier basis, clean glaciers exhibit more area loss on average from 1962 to 2006 (34%) compared to debris-covered glaciers (22%). Glaciers in this region of the Himalaya are shrinking at similar rates to those reported for the last decades in other parts of the Himalaya, but individual glacier rates of change vary across the study area with respect to local topography, percent debris cover or glacier elevations.
Highlights
Himalayan glaciers have generated a lot of concern in the last few years, with respect to potential consequences of glacier changes on the regional water cycle (Kaser et al, 2010; Immerzeel et al, 2010, 2012; Racoviteanu et al, 2013a)
In Sikkim, supraglacial debris covered an area of 78 ± 5 km2 in 2000 (14 % of the glacierized area)
Based on 1962 Corona and 2006 QuickBird imagery, we found an overall negative glacier surface area loss of 0.5 ± 0.2 % yr−1 since 1962, in agreement with those noted in other studies in the Himalaya
Summary
Himalayan glaciers have generated a lot of concern in the last few years, with respect to potential consequences of glacier changes on the regional water cycle (Kaser et al, 2010; Immerzeel et al, 2010, 2012; Racoviteanu et al, 2013a). The use of remote sensing for glacier mapping in this area is limited by frequent cloud cover and sensor saturation due to unsuitable gain settings and the persistence of seasonal snow, which hampers quality satellite image acquisition This area has very limited reliable baseline topographic data needed for glacier change detection, as discussed in detail in Bhambri and Bolch (2009). For eastern Nepal, 1970s topographic maps from Survey of India on a 1 : 63 000 scale are available, but their accuracy is not known with certainty Given these limitations, declassified Corona imagery from the 1960s and 1970s has increasingly been used to develop baseline glacier data sets, for example in the Tien Shan (Narama et al, 2010), Nepal Himalaya (Bolch et al, 2008a) and parts of Sikkim Himalaya (Raj et al, 2013)
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