The shrine of Amarnath in Jammu and Kashmir hit the headlines for a strange reason this summer. The shiva ling, a naturally-formed ice stalagmite in the Amarnath cave, melted. Public attention was suddenly called to global warming. Himalayan glaciers cover an area of about 23,000 sq km in India -- one of the largest concentrations of freshwater stored in glaciers outside the poles. Glacial melt makes about 30-50 per cent of the water in major northern rivers. Glaciers grew during the last glacial period known as Little Ice Age -- a cool period from 1550 to 1850. Since then, glaciers have retreated worldwide. Only, the rate of retreat has increased sharply in recent years.
The total surface area of glaciers worldwide has decreased 50 per cent since the end of the 19th century. The retreat has been stark in the Himalaya.The first warning came in 1999 from the Working Group on Himalayan Glaciology at the International Commission for Snow and Ice (icsi). It said Himalayan glaciers are receding faster than in any other part of the world and, and that they were likely to disappear by 2035.
The next major warning came in 2004 from the Sagarmatha project of the uk's Department for International Development (dfid). It gave a decade-by-decade analysis for Indian rivers over the next 100 years. A model developed under the project showed increasing river discharge at the source and flooding in the adjacent areas. It also stated that glaciers feeding the Ganga, Yamuna, Indus and the Brahmaputra rivers may be wiped out in 40 years. "In today's times, the rivers have shown 3-4 per cent surplus due to the 10 per cent increase in the melting of the glaciers of the western Himalaya, and the 30 per cent increase in the eastern Himalayan glaciers. In about 40 years, most of these glaciers will be wiped out and then we will have severe water problems," says Syed Iqbal Hasnain, vice-chancellor of Calicut University, who had led the study.
Indian scientists are divided over global warming's effect on glaciers. "Although these glaciers are the most sensitive parameters of temperature change, both positive and negative, I do not consider that global warming is a reason for this retreat. I believe that it is a simple cyclic episode," says Milap Chand Sharma, associate professor at the School of Social Sciences, Jawaharlal Nehru University (jnu), New Delhi. The data shows that the average melting under natural cyclic period is too insignificant post-1970; only about 10 metres a year.
wwf-Nepal has estimated that between 1971 and 1996, the Gangotri glacier retreated about 850 metres, that is, about 34 metres per year. According to the Geological Survey of India (gsi), Lucknow, the glacier retreated by two km in the two centuries prior to 1971, at an average of 10 metres per year. But the retreat was 870 metres between 1971 and 2001, with an annual average of of a shopping 30 metres (see table Breaking the ice ).
Himalayan glaciers are sensitive indices of climate change due to their peculiar vulnerability snow accumulation and melting on these depends on monsoonal precipitation as well as summer temperatures; winter precipitation has little impact. "As atmospheric temperature increases, more of the precipitation on glaciers will be in the form of rain and less of snow," says Hasnain.This would mean faster melting as the glacial ice would be more exposed in the absence of snow.
"gsi's studies in the 1970s established a direct relation between snowfall and glacier health. But since then, we have little data on snowfall and temperature in the Himalaya," says V K Raina, chair of the expert committee on Himlayan glaciology at dst. "Whatever little data is available shows a constant decrease in the annual snow precipitation in the Himalaya since 2000, with the year 2002 being an exception," says Raina. But occasional higher snow precipitation would hardly reverse the glacial retreat or make up for the lost ice, he adds.
Even the ipcc finds that atmospheric temperature has a greater impact on glacial retreat as compared to snowfall. Typically, for glaciers that are halfway between the equator and the poles (called mid-latitude glaciers), a 30 per cent decrease in cloud cover or a 25 per cent decrease in precipitation has an effect eqaul to that of a temperature increase of 1c. Moreover, even if snow precipitation is higher, a 1c rise in temperature would lead to 50 per cent increase in snow melting. Researchers at jnu analysed air temperatures across the Himalayas at an altitude of 4,000 metre above sea level. They observed an increase in average air temperature both in summer and winter months. They also noted a decline of 14 per cent in the average monthly snow cover in the western Himalaya; in the eastern Himalaya, the decline was 26 per cent.
The position of the snout, the lowest projection of the glacial ice, is an established indicator of its retreat. A study by jnu researchers on the Chhota Shigri glacier in Himachal Pradesh showed that temperature increase had resulted in its shrinkage by about 12 per cent in the past 14 years. An estimate by Sarfaraz Ahmad of Aligarh Muslim University revealed that the snout had retreated at the rate of 27 metre per year between between 1989 and 2000. Likewise, the Dokrani glacier -- one of the valley type glaciers of Gangotri group of glaciers in the Garhwal Himalaya -- receded by 550 metres, with an average rate of 16.6 metres per year between 1962 and 1995.
A team led by Anil Kulkarni of the Space Application Centre, Ahmedabad, recently investigated 466 glaciers in the Chenab, Parbati and Baspa basins. It noted an overall reduction in glacier area of 21 per cent--from 2,077 sq km to 1,628 sq km from 1962 to 2001. Said to be India's biggest ever programme to map and monitor Himalayan glaciers, it found greater fragmentation of glaciers, reflected in their increased numbers.
"Fragmented glaciers are more prone to melting as more surface area is exposed to heat," says Kulkarni. Since glacier response time is directly proportional to its depth, it could vary between 4 to 60 years, depending upon glacial size. This could be fundamental reason for large retreat of small glaciers. They conclude by saying that a combination of glacial fragmentation, higher retreat of small glaciers and climate change are influencing the sustainability of Himalayan glaciers.