Temporal and Spatial Changes of Glacial Lakes in the Central Himalayas and Their Response to Climate Change Based on Multi-Source Remote Sensing Data

Global warming has accelerated glacier retreat and glacial lake expansion in the central Himalayas, and the increase in glacial lake temperatures has affected underwater melting and avalanches of glaciers at the terminal edges of lakes. This has increased the risk of new types of hazards, such as glacier avalanches, ice-marginal slope instability, and glacial lake outburst floods (GLOFs), seriously threatening the lives and properties of downstream populations. Timely and accurate monitoring of the spatial distribution of glacial lakes and their dynamic changes in the central Himalayas are of great significance to understand regional climate change and prevent and mitigate disasters in the cryosphere. Therefore, we proposed a dynamic threshold method (Otsu) to automatically and accurately extract glacial lake boundaries in the central Himalayas, based on the enhanced normalized difference water index (ENDWI) calculated from multi-source remote sensing data (Sentinel-2 multi-spectral instrument (MSI)and Landsat series data) acquired from the Google Earth Engine (GEE) platform. Subsequently, we systematically analysed the spatial and temporal characteristics of glacial lakes and their response to climate change, and further explored the correlation between glacial lake expansion and the occurrence of GLOFs. Our results show that: 1) as of 2022, a total of 2562 glacial lakes have been identified in the Central Himalayas, with a total area of 257.48[[EQUATION]]10.46 km2 and total volume of 60.69[[EQUATION]]6.07 km3. Most of the glacial lakes in the Central Himalayas are located in the China-Nepal border area, and the glacial lakes are concentrically distributed in the elevation range of 3600-5900 m. 2) From 1990 to 2022, glacial lake expansion in the Central Himalayas was dominated by small glacial lakes, resulting in 847 new glacial lakes, and their total area and total volume increased by 88.61[[EQUATION]]4.64 km2 and 24.72[[EQUATION]]2.59 km3, respectively. Among them, four typical glacial lakes rapidly expanded along the direction of the glacier terminus as the mother glacier retreated. 3) Global warming and increased glacier melt water were the main drivers of glacial lake expansion; the frequency of GLOFs has shown a significant increasing trend since 1950, and ice avalanches were the main trigger for glacial lake outbursts. The glacial lakes in the region will continue to expand in the future, and the risk of GLOFs will increase; thus, research on the monitoring and risk assessment of glacial lakes in the central Himalayas should be strengthened. The results of our study can provide an important reference value for the protection of regional ecological security and sustainable development of water resources; they can also provide scientific support for the prevention and mitigation of regional natural disasters.