Himalayan Glaciers Melting: Lakes Appear at Higher Altitudes

Supraglacial lakes are increasingly forming on the ice surfaces of Himalayan glaciers, a trend highlighted by a recent three-decade study of 16 glaciers. Over this period, all examined glaciers showed an increase in these meltwater accumulations in their uppermost zones, a shift from previous observations. The study published in Springer's Journal of Earth System Science details how meltwater now gathers in surface depressions, even on ice previously less prone to lake formation.

Gangotri glacier in Uttarakhand exemplifies this change, with its total supraglacial lakes growing from 80 in 1992 to 129 by 2022. More strikingly, lakes in its highest relief zone increased from four to 15, tripling in combined area. Similar trends were observed on Bhutan's Chomolhari glacier, where seven new lakes appeared in its upper zone by 2022.

Researchers linked the upslope expansion of debris cover across these glaciers to stronger warming and reduced snowfall, particularly in the Central and Eastern Himalaya. This debris cover facilitates lake formation by creating differential melting. The merging of adjacent lakes, especially in lower zones, raises concerns about potential Glacial Lake Outburst Floods (GLOFs).

Regional variations exist, with some glaciers in the Karakoram, like Panmah, showing declines in lake numbers and area. However, the overall trend across the Himalaya indicates increasing lake formation. Supraglacial lake analysis is crucial for predicting future glacier behaviour and understanding water resource contributions in a changing climate.