Rapid Glacier Loss A Body Blow To Life In Nepal; Ag Output Falling Along With Water Supplies
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The glaciers around Kyanjin are melting fast. The Himalayan region could lose up to two-thirds of its glaciers by 2100. Image by Jonas Gratzer for Mongabay.
As Nepal’s glaciers melt, what’s left of the ice is often dusted with a layer of soot from distant polluting cities , mostly in India. Air pollution from India’s densely populated Indo-Gangetic Plains, one of the most polluted regions in the world, is speeding up the melting: the deposits of black carbon and dust trap solar radiation that would otherwise be reflected out by the white ice. Tracking the changes in mountain glaciers is among the best ways to keep tabs on climate change. Under the scenario of a 4°C temperature rise by 2100, two-thirds of the Himalaya’s glaciers will be washed down the Indus, Ganges, Brahmaputra and other great rivers fed by the ice pack.
Initially, the summer flow of these rivers will rise until 2050, according to estimates, but will drop off eventually as the amount of ice diminishes. The extent of that loss is already apparent — and severe. Between 1980 and 2010, Nepal lost a quarter of its glacier area, according to an ICIMOD study using satellite data. Every year, 8 billion tons of ice melt, without being replaced by new snow. Scientists have tracked changes in 650 Himalayan glaciers and identified a clear pattern: from 1975 to 2000, the glaciers’ surface shrank by nearly 23 centimeters (9 inches) a year, a number that steadily rose between 2000 and 2016, when the glaciers experienced an annual loss of about 43 cm (17 in).
Langtang National Park is a true gem for tourists, but even tourism may soon be risky business in Nepal. Image by Jonas Gratzer for Mongabay
Over the millions of years that glaciers form, they’re in a constant state of flux. They expand, cleave through rocks, and carve valleys through the mountains. And all the while, along their edges, they build up walls of rock debris known as moraine. When the glaciers melt and form lakes, these moraine dams are all that hold the water back.
Most glacial lakes in the Himalayas today formed during the latter half of the 20th century, and satellite data show their numbers are rapidly growing. For the communities that live near them, this translates into an increased risk of glacial lake outburst flood (GLOF), which occurs when large volumes of meltwater cause the lakes to burst their moraine banks. A GLOF event in Kedarnath, India, in 2013, fueled by a torrential downpour rather than meltwater, killed thousands of people and affected more than 100,000 others. In Nepal, 21 glacial lakes are considered at high risk of a GLOF event. Records show that such events in the Himalayas occur every three to 10 years. In a warming climate, their frequency is expected to rise.
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https://news.mongabay.com/2021/12/as-its-glaciers-melt-nepal-is-forced-into-an-adaptation-not-of-its-choosing/
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