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Debris cover is not protecting Himalayan glaciers
The glacier melt areas in the Himalayas are experiencing a significant loss of ice due to global warming, despite the presence of a blanketing layer of debris over half of the area, a new study found. The study , conducted by the Pune-based Indian Institute of Science Education and Research (IISER), focused on the observed rate of ice loss between the melt areas covered under debris and those without, and explained why the areas covered by thick layers of rock and debris are experiencing an equally significant loss of ice as their counterparts.
Such areas comprise 50% of the glacier melt areas in the mountain range, and will continue to lose more ice compared to the debrisfree areas in the long run, the IISER study warned.
According to lead researcher Argha Banerjee, assi stant professor (earth and climate science) at IISER, the typical high and steep valley walls surrounding Himalayan glaciers supply a lot of rock debris, leading to a layer of debris on the lower melt-zone that acts as an insulating blanket, reducing ice melt.
Banerjee told TOI that shrinking glaciers in the Himalayas have a profoundly negative effect on water security, including water needs for agriculture and hydropower generation, for people living in the Indus basin and in the upper reaches of the Ganga-Brahmaputra basin.
Glacial meltwater supply, Banerjee said, acts to sof ten the impact of drought in these areas.
“Glacier shrinkage exposes mountain people to increased risk from hazards like glacial lake outburst floods,“ he said.
The IISER study was recently published in the international journal, `The Cryosphere'.
Melting of glaciers
Himalayan glaciers shrank 16% in 50 yrs: Isro
Bangalore: Himalayan glaciers retreated by 16% in the last nearly five decades due to climate change, investigations by India’s scientists in selected basins in four states has revealed. The retreat of Himalayan glaciers and loss in a real extent were monitored in selected basins in J&K, Himachal Pradesh, Uttaranchal and Sikkim, under a programme on space-based global climate change observation by Indian Space Research Organisation (Isro).
“Investigations on glacial retreat were estimated for 1,317 glaciers in 10 sub-basins from 1962. This has shown an overall reduction in glacial area from 5,866 sqkm to 4,921 sqkm since 1962, showing an overall de-glaciation of 16%”, says the latest annual report of Isro. Snow cover monitoring of all basin has been completed, it said.
Atlases for three years are ready and one for the fourth year is being prepared. Modeling response of Himalayan cryosphere to climate change has been initiated, Isro added. Meanwhile, a study on the impact of temperature and carbon dioxide (CO ² ) rise on the productivity of the four major cereal food crops — wheat, rice, maize and pearl millet — revealed that yield of all of them showed reduction with increasing temperature.
Assessment after taking field data showed that wheat was the most sensitive crop and maize the least sensitive to temperature rise among the four, Isro pointed out. Another study for climate change impact on hydrology was carried out using “Curve Number” approach to study the change in run off pattern in India at basin level. “Analysis shows there will be significant increase of run off in the month of June in most of the major river basins”, the 2009-10 report of the Isro said. Isro has also observed a strong correlation between agriculture vegetation (mainly rice areas) and methane concentration.
Rate of retreat of Gangotri slows: 1974-2008-2016
The rate of retreat of Gangotri glacier has slowed down to 11 metres since 2008 from the maximum of 35 metres recorded in 1974, according to experts at the Almora-based GB Pant National Institute of Himalayan Environment and Sustainable Development (GBPNIHESD) who conducted a study of the glacier located in Uttarkashi from 2008 till 2016. While this is good news, scientists said that the worrying part is that the base of the 30-km long glacier is thinning and has become more fragile.
Kireet Kumar, scientist at GBPNIHESD, who was involved in the study , told TOI, “We are not much concerned about the receding of the glacier since it is not so drastic. Our concern is more about the mass loss. Due to thin ning of its shape, Gangotri glacier has become vulnerable to fragmentation which would ultimately lead to breakage and loss of water.“
Melting twice as fast since 2000
Ice Loss Indicates Devastating Future For Region And Hundreds Of Millions Who Depend On It For Water
Climate change is “eating” the glaciers of the Himalayas, posing a grave threat to hundreds of millions of people who live downstream, a study based on 40 years of satellite data has shown.
The study, published in ‘Science Advances’, found the glaciers have lost a foot and a half of ice every year since 2000, melting at a far faster pace than in the previous 25-year period. In recent years, the glaciers have lost about eight billion tonnes of water a year. The study’s authors described it as equivalent to the amount of water held by 3.2 million Olympic-size swimming pools.
The study adds to a growing and grim body of work that points to the dangers of global warming for the Himalayas, which are considered the water towers of Asia and an insurance policy against drought.
In February, a report warned that the Himalayas could lose up to a third of their ice by the end of the century, even if the world fulfills its goal of keeping global average temperatures from rising only 1.50 above preindustrial levels.
That goal, which scientists have identified as vital to avert catastrophic heat waves and other extreme weather events, is nowhere close to being met. Average global temperatures have risen by one degree already in the last 150 years. Greenhouse gas emissions continue to climb. And scientists estimate that we are on track to raise the average global temperature between 30 to 50 Celsius by the end of this century.
Another study, published in May, found that Himalayan glaciers are melting faster in summer than they are being replenished by snow in winter. In the warm seasons, meltwater from the mountains feeds rivers that provide drinking water and irrigation for crops.
In the Himalayas, the loss of glaciers poses two profound risks. In the short term, melting glaciers leave behind rock debris that creates dams, and if these debris dams burst, the resulting floods could destroy villages. In the long term, the loss of glacier ice means the loss of Asia’s future bank of water — a safeguard against periods of extreme heat and drought. Receding glaciers can also threaten the ecosystems they support, which can in turn affect communities in the region.
The latest study, led by researchers at Columbia University, relied on the analysis of satellite images of 650 glaciers across 2,000km of the Himalayas, including recently declassified US spy satellite data. The researchers turned the images into 3D models that showed changes in the area and the volume of the glaciers.
They found that from 1975 to 2000, glaciers lost 10 inches of ice each year. Starting in 2000, the rate of loss doubled, to about 20 inches each year. The study also concluded that while soot from fossil fuel burning is likely to have contributed to the ice melt, the bigger factor was rising temperatures. While temperatures varied across the vast mountain range, on average, they rose faster between 2000 and 2016 compared with earlier years. NYT NEWS SERVICE
6 glaciers receding 13-33 mm/year: 2013-2018
Six Himalayan glaciers monitored by the National Centre for Polar and Ocean Research (NCPOR) have been retreating in the range of 13 to 33 millimetres per year, the government said on Tuesday. The NCPOR has undertaken studies in the western Himalaya in Chandra basin in Lahaul-Spiti since 2013, minister for earth sciences Harsh Vardhan said. A total of six glaciers — Sutri Dhaka, Batal, Bara Shigri, Samudra Tapu, Gepang Gath and Kunzum — are monitored for mass, energy and hydrological balance, he said. “The rate of melting varies from glacier to glacier depending on topography and climatic variability of the region,” he said. PTI