Gangotri glacier ‘defies’ global warming

LUCKNOW: Amid the raging debate on how far the Paris COP21 deal on climate would limit the impact of global warming, here is a heartening news from a Lucknow University professor: the rate of retreat of Gangotri glacier, the source of sacred river Ganga, has come down to 10 metre in 2015 from 22 metres in 2001.
Dhruv Sen Singh, an expert on glaciers, who was part of the first and second Indian expeditions to the Arctic in 2007-08, has found this during his recent visit to Gangotri.The glacier, said Singh, is no doubt retreating but the average rate of recession has come down. “Even if the present rate of retreat continues, it would take about 2,500 years for its complete disappearance of 30-km long glacier,’’ said Singh.
Global warming is said to be responsible for melting of glaciers across globe. However, Prof Singh feels that the decreasing rate of retreat of Gangotri glacier indicates that global warming is not the only reason for melting of glaciers and that the fears of global warming appear to be exaggerated.
Prof Singh's findings support those of Geological Survey of India which recorded that the Gangotri glacier retreated at the rate of 22 metre per year between 1985-2001 and 35 metres per year between 1956-77.
Significantly, the IPCC 2007 report on glaciers world over had predicted that Gangotri glacier would disappear by 2035 due to global warming. However, in 2010, the IPCC retracted its statement on Gangotri glacier.
Singh, who visited Gangotri glacier in 2001 and the same spot in this year, said “I realised that the rate of retreat is normal because the melting of glacier is a normal physical process if the temperature is above zero degree Celsius.” Both his visits were from August to October, the period which is considered as summer season for glaciers.
For measuring the retreat, Singh used `lateral moraines' as a base point. He measured the distance between the snout (end point of glacier) and the base point through laser range finder. “The base point was the same both in 2001 and 2015. However, this time, I found that the glacier existed beyond the base point leading to a conclusion that the rate of retreat has reduced,” explained Singh.
The findings were similar to the report Prof Singh published in 2001 along with Prof Ajai Mishra of his department in LU. They had concluded in 2001 that the global warming is not the only factor responsible for rapid rate of retreat of Gangotri glacier for which it has attracted international attention.
“We found that there are other local factors responsible for melting and retreating of the Gangotri,” said Prof Singh.
First, he said, at Gaumukh, the end point of Gangotri, there is no fresh snow but covered with debris known as supra-glacier moraine. The albedo (ratio of incoming and outgoing solar radiation) is 70-80% for fresh snow and only 30-40% for the debris, a reason why the glacier melts at a rapid rate.
Second, Singh added, in his recent (2015) visit he found that snout of the glacier is cracking and falling because of a geographical structure called lineament.
Third there are number of supra glacial lakes (lakes above glaciers) which leads to high melting.
Fourth, some of its tributaries had become inactive and were contributing water instead of ice, leading to fluctuations in rate of retreat of high mountain glacier.
Singh argued that if global warming is the only reason, all the glaciers should retreat at the same rate. However, all Himalayan glaciers are retreating at different rates and some are advancing too, said Singh. He further said that if glaciers are melting at a faster rate due to global warming, the discharge of the river should increase, leading to a wide valley. “Due to global warming, the temperature will increase which will increase the rate of evaporation, and so the cloud formation resulting in precipitation. The increased precipitation in high latitude would have glaciers expand and advance rather than retreat and shrink,’’ he claimed.
Union environment minister Prakash Javadekar on Monday said as many as 248 of 2,018 (12.3%) Himalayan glaciers observed for a study are “retreating’’ (melting away) while 18 are advancing (growing). The minister also revealed that a majority - about 87% - of the glaciers observed had remained stable. These results came up during a study conducted on a part of the glaciated region of the Himalayas between 2004 and 2011 by Indian Space Research Organisation (ISRO) in collaboration with the ministry of environment and forests (MoEF).
Scientific data indicates that glaciers during Pre-Cambrian (540 million years ago), Gondwana (250 million years ago), and Pleistocene Period (1 million years ago) retreated and melted much before the existence of man on the planet. “The Cretaceous period 65 million years ago was the hottest in the history of the earth. Man was not around at the time,’’ Singh said.