Glaciers are the main sources for rivers originating in the Himalayas. They are also the main sources of water for the millions who live in the Gangetic Plains. Hence, they need to be monitored regularly. But studies on Himalayan glaciers mostly concentrate on two-dimensional changes: glacier length and area. Moreover, they focus only on a limited number of glaciers. Some of which seem to retreat while some others are advancing. Recent reports suggest the need to study more parameters to determine how these glaciers respond to climate change in a more holistic manner.
So Aparna Shukla and Purushottam Kumar Garg from the Ministry of Earth Sciences, New Delhi and the Wadia Institute of Himalayan Geology, Dehradun undertook such a multidimensional study. They focussed on the Panchi Nala glacier in the Bhaga River basin of the Lahaul-Spiti District, Himachal Pradesh. The region experiences the monsoon in summer and the westerlies in winter. Thus, the glacier is suitable for studying the effects of annual meteorological phenomena. Data from a meteorological station near the snout, maintained by the Snow and Avalanche Study Establishment, Government of India, helped interpret satellite images, even those of inaccessible regions of the glacier.
The team used multi-temporal and multi-spectral remote-sensing satellite data from available sources and estimated the outlines of the glacier, of glacial lakes and of debris-covered areas. From images at different wavelength bands, taken during 1971-2016, the researchers extracted changes in glacier length, area, debris cover, snowline altitude, surface ice velocity, and surface elevation in the Panchi Nala glacier. They also measured glacier debris thickness at the location using a handheld Global Positioning System during the first week of October 2016 to verify data from the satellites.
There was a twenty-three per cent increase in debris cover during the entire period, they report.
“The snowline drifted up by two hundred and eighty metres during these forty-six years,” says Aparna Shukla, Ministry of Earth Sciences.
In lower regions, the team noted the development of many lakes on top of the glaciers. Between 1992 and 2016, the average surface ice velocity of the glacier reduced by thirty-four percent.
“All this collectively suggests severe glacier degeneration,” says Purushottam Kumar Garg. “Considering a warming trend and monotonic decrease in snowfall in the region, glaciers are likely to exhibit accelerated wastage”.
The study highlights the need for raising public awareness and initiating an urgent action plan to mitigate the adverse effects of glacial retreat.
Geomorph., 341: 1-14 (2019);
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