Gangotri holds ground after decades of retreat

The recession was maximum between 1968 and 1980: Studies

After more than four decades, the Gangotri glacier has arrested its decline. It is not retreating as fast as it did since 1968, scientists have found.

Between 2001 and 2006, the mighty glacier retreated by about seven meters every year. However, the retreat was more than 21 meters every year between 1968 and 2001.

With a length of about 30 kms, Gangotri is the largest glacier in the Garhwal Himalayas. The Bhagirathi river originates from its snout – known as Gaumukh-at an elevation of 3,950 meters above the sea level.

Analysing declassified high-resolution images from two US spy satellites, Corona and Hexagon, together with images from India's Cartosat-1, researchers from the Wadia Institute of Himalayan Geology in Dehradun and University of Zurich precisely measured the rate of recession for Gangotri.

The recession was maximum between 1968 and 1980 when the gigantic river of ice was truncated by about 26.9 meters every year. Though the retreat slowed down a bit in the next 20 years (between 1980 and 2001), it was still very high as the glacier was withdrawing at a rate of 21 meters every year.

Since 2001, the retreat halted substantially. The reasons, however, are unclear.
The annual withdrawal between 2001 and 2006 matches well with that between 1965 and 1968 when Gangotri receded by 5.9 meters every year, scientists said, adding that previous studies had overestimated Gangotri recession.

“Our results suggest that in recent times (2001-2006) Gangotri glacier has lost fewer area. The recession declined compared to previous observations but it does not imply that recession has ceased,” the researchers reported in the latest issue of the journal ‘Current Science.’

Published field surveys by the Geological Society of India closely match the findings of satellite-image based research giving the scientists confidence on the accuracy of their data on the slowing down of Gangotri.

For instance satellite tells that Gangotri receded by about 764 meters between 1968 and 2001 whereas field survey showed that it lost about 720 meters of length from 1971 to 1996.

“The findings could be of help in understanding more precisely the short term intervals of glacier advance and retreat vis-a-vis climatic fluctuation in a region and may not necessarily be related to the so called global warming phenomena,” geologist Rajeev Upadhyay from Kumaun University in Nainital told Deccan Herald.