Glacial lake outburst debris flows in the Himalayas in response to climate change

Global warming has led to environmental changes in the alpine Himalayan mountains, with significant glacier retreat, an increase in the area and number of glacial lakes, and an increase in the frequency and scale of glacial lake outburst debris flows, causing significant damage to people and facilities in downstream. In this study, we analyzed the spatial heterogeneity and variations of disaster-forming environments on the north and south areas of the Himalayan, identified the distribution patterns of glacial lake outburst debris flows, and predicted debris flows’ changing trends in the Himalayas. The results demonstrate that the distribution and variations of glaciers and glacial lakes in the Himalayan region have apparent spatial heterogeneity. The Central and South Himalayas are where glaciers and glacial lakes undergo the most dramatic changes. Glacial lakes are widely distributed in the Central Himalayas and southern slopes, with an increase in area and number from 1990-2015. New glacial lakes at higher elevations and alterations in moraine lakes dominate glacial lake variations across the region. Since the 20th century, there have been 249 outbursts of 113 glacial lakes in the Himalayan, Karakorum, and Southeast Tibetan regions, with the majority of outbreaks occurring in the Central and Eastern Himalayas along steep sections of main rivers. In the period 1901-2019, the inflection point for glacial lake outburst hazard is 1966⁺³⁷/_-31 years (median and 95% HDI), and the frequency of glacial lake outbursts proliferates before the inflection point and slowly increases after the break-point; the annual mean temperature changes have opposite trends before and after the inflection point, reflecting the lag effect of glacial lake outbursts on temperature changes. In addition, the measured data were calibrated and down-scaled the future simulated climate prediction data to reveal the spatial and temporal trends of glacial lake outburst debris flow disaster risk under the influence of future climate-causing factors. The annual mean temperature and precipitation in the Himalayas generally exhibited an upward trend in the 21st century, with higher increment speeds of warming and humidification on the northern slopes; Increasing very high and high glacial lake outburst debris flow hazard zones are a consequence of climate change, with a more concentrated distribution in the centre and northwest of the Himalayan Mountains.