2019 Study by American Researcher Warned Himalayan Glaciers Melting

NEW DELHI: On Sunday, February 7, a part of the Nanda Devi glacier broke off in Uttarakhand's Chamoli district, causing massive floods. The glacier burst at Joshimath led to a massive flood in the Alaknanda river system and caused large-scale devastation.

This devastation recalled a 2019 study that warned about the dangers of climate change and said Himalayan glaciers have been melting twice as fast since the start of this century.

A study published two years earlier in June 2019 in the journal Science Advances, indicated that glaciers have been losing the equivalent of more than a vertical foot and half of ice each year since 2000, which is double the amount of glacial mass loss that took place from 1975 to 2000.

The study is based on 40 years of satellite observations across India, China, Nepal and Bhutan, showed that climate change is melting the Himalayas' glaciers.

"This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why," said Joshua Maurer, a PhD candidate at Columbia University in the US.

While the amount of mass lost from the glaciers was not specifically calculated in the study, the glaciers may have lost as much as a quarter of their enormous mass over the last four decades, according to Maurer, the lead author of the study. The study amalgamated data from across the region, stretching from early satellite observations to the present. The data shows that the rate of melting is consistent, and that rising temperatures are to blame, the researchers said.

Temperatures vary from place to place, but from 2000 to 2016 they have averaged one degree Celsius higher than those from 1975 to 2000, they said. Researchers studied repeat satellite images of some 650 glaciers spanning 2,000 kilometres from west to east.

Many of the 20th-century observations came from declassified photographic images taken by the US spy satellites. The researchers created a computerized system to turn these images into three dimensional (3D) models that could show the changing altitudes of glaciers over time.

The researchers then compared these images with images taken after the year 2000 by more sophisticated satellites, which more directly show the changes in altitude. They found that from 1975 to 2000, glaciers across the region lost an average of about 0.25 metres of ice each year in the event of slight warming. Following a more distinct warming trend starting in the 1990s, starting in 2000 the loss hastened to about half a metre annually.

Researchers noted that Asian countries are burning greater amounts of fossil fuels and biomass, sending soot into the sky, adding much of it eventually lands on snowy glacier surfaces, where it absorbs solar energy and hastens melting.

They collected temperature data during the study period from ground stations and then calculated the amount of melting that observed temperature increases would be expected to produce. Those figures were then compared to the data of what actually happened.

The researchers said that while the Himalayas are generally not melting as fast as the Alps in Europe, but the general direction of the situation is similar.

The researchers took note that some 800 million people depend in part on seasonal runoff from Himalayan glaciers for irrigation, hydropower and drinking water.

The accelerated melting appears so far to be increasing runoff during warm seasons, but scientists think that this will decrease within decades as the glaciers lose mass. According to the researchers, this will eventually lead to water shortages.

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