GANGTOK, November 10: While challenging the internationally accepted view that Himalayan glaciers are receding due to global warming, a discussion paper by Union Ministry of Environment and Forests (MoEF) has explicitly stated that one cannot correlate the impact of global warming on the glaciers on the basis of these small time variations in Sikkim with glacier mass degeneration lowest in Sikkim among all the Himalayan States.
Brought out by V.K. Raina, former Deputy Director-General, Geological Survey of India, for the Ministry of Environment and Forests, the discussion paper ‘A State-of-Art Review of Glacial Studies, Glacial Retreat and Climate Change’ on the Himalayan glaciers points out that it was premature to make a statement that the glaciers were retreating abnormally because of global warming.
The glaciers, although shrinking in volume and constantly showing a retreating front, have not in any way exhibited any abnormal annual retreat of the order that some glaciers in Alaska and Greenland have reported, the report states which was released by Environment Minister Jai Ramesh yesterday in Delhi.
Releasing the documents, Ramesh said that while most Himalayan glaciers were retreating, some were advancing as well. This included the Siachen glacier.
According to the report, all glaciers under observation in the Himalayan region during the past three decades have shown cumulative negative mass balance (determined by annual snow precipitation). Degradation of the glacier mass has been the highest in Jammu and Kashmir, relatively lower in Himachal Pradesh, even less in Uttarakhand, and the lowest in Sikkim - showing a declining trend from the north-west to the north-east.
The report has given a special chapter on Sikkim where it points out that the studies carried in Sikkim in the past 3 decades have revealed that individually, glaciers behave in a different manner to factors beyond the climate such as morphology of valley, shape and size, aspect and slope and other factors.
“However, there are a large number of glaciers which retreated fast, yet there are other glaciers which advanced during the same period of analysis”. The average rise of ELA in Sikkim stands at 47m and there are 10 glaciers which show large rise in ELAs, the report states. There are also 8 glaciers which had little rise in the ELA, the report said adding that there are other glaciers which show depression in ELAs during these 30 years.
Meanwhile, the total ice reserve in Sikkim has reduced to 25.7029 m3 in 2005 from 26.2986 m3 in 1976.
Sikkim has around 84 glaciers covering a total of 691.5 square kms with a snowfield area of 251.22 square kms, official data chronicled through Remote Sensing system last year revealed.
Out these 84 glaciers, Zemu glacier the source of River Teesta is the largest and is located at North Sikkim and its size is around 90.94 sq kms.
The report reveals that the average rate of retreat of glaciers in Sikkim has been calculated to be about 13.02 m per year from 1976 to 2005. Out of 26 glaciers analyzed, 12 glaciers had retreated at a faster rate than average (13.02 m per year), Zemu (14.10 m per year), Tista (14.83 m per year), Jongsang (38.2 m per year), S Lhonak (33.10 m per year), Changsang (22.37 m per year), Lhonak (27.10 m per year), E. Langpo (23.97 m per year), Rathong (18.20 m per year), S. Simpu (17.27 m per year), Umaram (14.03 m per year), N. Lhonak (13.27 m per year) and Tonsang (14.00 m per year). Rest of the glaciers, have shown a below average retreat rate.
The report states that from Zemu glacier has retreated approximately 863 m. However, the retreat was punctuated between 1988 and 2000 with an advanced of 92 m. (7.67 m per year). The areal coverage of glacier increased during this period, it is informed. In a nutshell, Zemu glacier retreated between 1976, advanced for 12 years and again retreated thereafter.
“One can not correlate the impact of global warming on the glaciers on the basis of these small term variations in Sikkim”, the report states. It further stated that these variations at short time scale may be helpful to see the ‘weather change’ but not the ‘climate change’.
A key finding by the study group of all glaciers in the Himalayas from mid 1970s till date which could prove vital for the commission constituted by Sikkim on glaciers was all the glaciers under observation, during the last three decades of 20th century have shown cumulative negative mass balance.
“Degeneration of the glacier mass has been the highest in Jammu & Kashmir (single glacier, 10 years record), relatively lower in Himachal Pradesh ( 3 glaciers, 10 years record), even lower in Uttarakhand (one glacier, 10 years record) and the lowest in Sikkim (one glacier,10 years record)”.
Another key finding that glaciers like Gangotri, Bhagirathkharak and Zemu which had hitherto been showing a rather rapid retreat, along its glacier front, at an average of around 20m per year till up to 2000 AD, has since slowed down considerably, and between September 2007 and June 2009 is practically at a standstill. It is premature to make a statement that glaciers in the Himalayas are retreating abnormally because of the global warming, the report states.
It was in 1965 that a slight deviation - very little – but significant, in the form of assessment of glacier ice thickness by geophysical methods- Seismic and Resistivity was initiated at the Zemu glacier (Sikkim). For the first time it was scientifically established that a glacier of the size of Zemu had ice thickness of above 200m, about a kilometre up stream of the snout, it is informed.