Melting into thin air

The 25-km long Gangotri glacier, fountainhead of the Ganga, is receding at an average 18 metres annually

 
Last Updated: Sunday 28 June 2015

Melting into thin air

B etween 40 and 50 million years ago, the Indian subcontinent collided with the rest of the Asian landmass. This collision caused the Earth's crust to buckle and rise forming the Himalaya. The uplift of the Himalaya was a gradual process over a long period. As the elevation of the mountains rose above the permanent snowline, it was transformed into "the abode of eternal snow and ice" forming the glaciers. For over two million years, these glaciers have sculpted the Himalayan landscape and influenced the course of human history.

"Himalayan glacial snowfields store about 12,000 cubic kilometres of freshwater and have a significant cooling affect in the entire region," says Bahadur. "The moisture-laden environment acts as a coolant for the region, thus creating an area of mega-biodiversity in flora and fauna."

"These glaciers are, in turn, affected by various factors such as changes in the energy output from the Sun and anthropogenic (or human-induced) changes," says Bahadur. But the receding and thinning of glaciers can be blamed primarily on the increase in emission of greenhouse gases.

Scientists had expected the five-kilometre-long Dokriani Bamak glacier in Himachal Pradesh to grow after a severe winter in 1997. Instead, it retreated by 20 m in 1998, compared to an annual average of 16.5m over the past five years. "This is a phenomenal melt rate," says Joseph Gergan, a geologist at the government-run Wadia Institute of Himalayan Geology ( wihg ) at Dehradun.

But Dokriani Bamak is just one of several glaciers that feed the Ganga. The Gangotri glacier, too, has been receding alarmingly in recent years, says Bahadur. "From observations dating back to 1842, the rate of recession of the snout -- the point at which the glacier ice ends -- has been found to have increased more than two-and-a-half fold per year," he says. Between 1842 and 1935, the glacier was receding at an average of 7.3m every year, whereas between 1935 and 1990, the rate of recession had gone up to 18 m a year. "The increase can be ascribed in part to the phenomenon of global warming and also to the environmental impact of increasing human activities in the Himalaya," he says. All these affect precipitation which is the source of nourishment for the glaciers, says Hasnain.

The glaciers in the Western Himalaya are fed by winter and summer precipitation. But those in the eastern and central Himalaya get their nourishment only from summer precipitation. "With only the summer precipitation to depend on, the glaciers in the eastern and central Himalaya have the dual problem of receding snowline and decreased precipitation due to global warming," says Hasnain. "Besides, accumulation and melting of snow takes place at the same time in these glaciers."

Hasnain has another dimension to add, "The recession is also the highest in the central and eastern Himalayan glaciers because, compared to the rest of the world, the population density near these glaciers is very high." Most of the people living in this area are economically backward and the consequent deforestation has adversely affected the glaciers, adds Bahadur.

It is important to understand that, in summer, there is a higher probability of precipitation resulting in rain than in winter, explains Hasnain. In cases where temperatures are higher than normal years, there are three negative effects on glaciers: increased proportion of rain in the precipitation which reduces accumulation by snowfall; higher temperatures increase melting; and decreased albedo due to decrease of snowfall.

The wghg , of which Hasnain is chairperson will submit its final report to icsi in July 1999. "Ironically, we have very little information on India because, apart from the possible causes of recession, we do not have many weather monitoring stations near glaciers to collect information and create a database," says Hasnain. "The glaciers in Nepal are better monitored. Our government is totally blind to the urgency of the problem. Just one glacier monitoring station has been set up and that stopped functioning within two months," he says.

Hasnain is also a member of the Flow Regime from International Experimental and Network Data ( friend ), an organisation recently launched by Nepal, Bhutan, Pakistan, China and Bangladesh to study the glaciers. "Strangely, India is not participating in this very important regional activity supported by unesco ," says Hasnain. "It is beyond my comprehension why the government is ignoring these initiatives, though the Himalayan waters are the lifeblood of millions of Indians."

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.