Abstract
The continuous melting of valley glaciers can impact the water levels of glacial lakes and create glacial lake outburst floods (GLOFs). The Xixabangma massif is one of the most populated areas in the Himalayas and has suffered from multiple GLOFs. To estimate the glacier melting rate in the past four decades and analyze the outburst risk of glacial lakes in the Xixabangma massif, we determined changes in glacier mass balance, glacier area and glacial lake area based on KH-9 images, TanDEM-X images, Landsat images, SRTM DEM and ICESat-2 elevations. Our results show that, from 1974 to 2018, the total glacier area shrank from 954.01 km2 to 752.46 km2, whereas the total glacial lake area grew from 20.90 km2 to 38.71 km2. From 1974 to 2000, 2000 to 2013 and 2013 to 2018, the region-wide glacier mass balance values were −0.16 m w.e./a, −0.31 m w.e./a and −0.29 m w.e./a, respectively. Three glacial lakes, named Gangxico, Galongco and Jialongco, respectively, expanded by 127.14%, 373.45% and 436.36% from 1974 to 2018, and the mass loss rates of their parent glaciers from 2000 to 2013 increased by 81.72%, 122.22% and 160.00% relative to those during 1974 to 2000. The dams of these three lakes are unstable, and their drainage valleys directly connect to a major town and its infrastructure. Due to current high-water levels, possible external events such as ice collapse, landslide, heavy rainfall and earthquakes can easily trigger GLOFs. Hence, we deemed that the Gangxico, Galongco and Jialongco glacial lakes are dangerous and require special attention.
Highlights
Glacier mass loss can directly affect the stability of a glacial lake, so the quantitative estimation of glacier mass balance can help to assess the hazard of glacial lake outbursts [5]
1974 to 2018, the glacier area shrank by 201.55 km2 (−0.48%/a), whereas the glacial lake area expanded by 17.81 km2 (1.94%/a)
Raina et al [47] (p. 43) reported a mass balance of −0.16 m w.e./a from 1979 to 1982 for the Changme Khangpu glacier in the Everest region, as derived by in situ glaciological measurements; Bolch et al [24] derived a mass balance of −0.18 m w.e./a from 1970 to 2007 for the Lhotse Nup glacier in the Everest region based on KH-4B and Cartosat-1 stereo images; Maurer et al [23] derived a mass balance of −0.17 m w.e./a from 1974 to 2006 for glaciers in the Bhutan–China border based on KH-9 and ASTER stereo images
Summary
The Himalayas host more than 12,000 glaciers that cover an area of approximately. Since the 1950s, climate warming has aggravated glacier ablation in the Himalayas [4], and many proglacial and supraglacial lakes, which are located in the upstream parts of valleys, have emerged after glaciers have experienced constant backwasting and retreating. As temperature maintains its high level, glacier mass loss will continue and more meltwater will gather in glacial lakes. Some glaciers connected to proglacial lakes will experience an accelerated retreat, leaving more space for glacial lake expansion. Glacier mass loss can directly affect the stability of a glacial lake, so the quantitative estimation of glacier mass balance can help to assess the hazard of glacial lake outbursts [5]. Glacier mass balance can be measured in several ways, including in situ measurements
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