Abstract
The Sikkim Himalayan glaciers and glacial lakes are affected by climate change like other parts of the Himalayas. As a result of this climate variability in the Sikkim Himalaya, a detailed study of the Gurudongmar lake complex (GLC) evolution and outburst susceptibility assessment is required. Glacial lake volume estimation and lake outburst susceptibility assessment were carried out to reveal different characteristics for all four lakes (GL-1, GL-2, GL-3, and GL-4) from the lake complex. Each of these lakes has a moderate to very high potential to outburst. As the dam of GL-1 provides no retention capacity, there is a very high potential of a combined effect with the sudden failure of the moraine-dams of GL-2 or GL-3 located upstream. Temporal analysis of GLC using optical remote sensing data and in-field investigations revealed a rapidly increasing total lake area by ~74 ± 3%, with an expansion rate of +0.03 ± 0.002 km2 a−1 between 1962 and 2018 due to climate change and ongoing glacier retreat. The overall lake area expansion rates are dependent on climate-driven factors, and constantly increasing average air temperature is responsible for the enlargement of the lake areas. Simultaneously, changes in GLC expansion velocity are driven by changes in the total amount of precipitation. The deficit in precipitation probably triggered the initial higher rate from 1962 to 1988 during the winter and spring seasons. The post-1990s positive anomaly in precipitation might have reduced the rate of the glacial lake area expansion considerably.
Highlights
Glaciers’ response to climate change has been clearly observed throughout the world [1]
Sometimes failures occur due to undercutting slopes by glacio-fluvial erosion and monsoon-induced heavy rainfall leading to saturation and erosion of frontal moraine slopes or loose rock structures hanging over the lakes, together leading to cataclysmic Glacial lake outburst floods (GLOFs) events [12,13]
All the satellite images and SRTM DEM have been obtained from the United States Geological Survey (USGS) portal
Summary
Glaciers’ response to climate change has been clearly observed throughout the world [1]. Glacial lake outburst floods (GLOFs) are common in all areas where glacier retreat is reported. A rapid outburst of glacial lakes can cause a catastrophic flood in the downstream region with great erosive power and debris transport capacity in a short period of time [5,6,7,8,9]. This is caused by dam breaching or overtopping with a large variety of different triggers, according to local lake position, surrounding landscape, and other natural conditions. Sometimes failures occur due to undercutting slopes by glacio-fluvial erosion and monsoon-induced heavy rainfall leading to saturation and erosion of frontal moraine slopes or loose rock structures hanging over the lakes, together leading to cataclysmic GLOF events [12,13]
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