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.Glaciers in the Qinghai-Tibet Plateau, the watershed for several Himalayan rivers, have been shrunk by 15 per cent in the past three decades and the situation could worsen in future due to global warming, Chinese scientists said on Wednesday
Long known as the “roof of the world,” the Tibetan Plateau is about the size of Western Europe and supplies water to nearly 2 billion people in Asia as the source of several major rivers, including the Yangze, Mekong, Salween (Gyalmo Ngulchu), Indus, Brahmaputra and Yellow rivers. But because of the impact of climate change, the glaciers are retreating rapidly, grasslands are shrinking as desertification expands, regional precipitation has become irregular, water levels are dropping in major rivers and the permafrost is thawing. The melting of Tibetan glaciers, the largest mass of frozen fresh water outside the polar regions, is linked to many environmental consequences both locally and globally, including heat waves in Europe, according to some studies.
Glacial retreat
Chinese officials estimate Tibet holds 14.5 percent of the world’s total glacier mass. While there are a few different theories on what is causing the glaciers to melt, researchers agree the pace is staggering. China's state-run Xinhua news agency reported in April that an average of 247 square kilometers of glacier is disappearing annually, and that some 7,600 square kilometers of glacier, or about 18 percent of the total, has disappeared since the 1950s. Zhang Mingxing, a Chinese official who heads the Tibet Mountaineering Administration, said the glacier at the Everest base camp, 5,200 meters above sea level, has already disappeared. “There is nothing but stones,” he was quoted as saying by Xinhua.
Herders graze their yak in the grasslands of the high Tibetan Plateau in the county of Naqu, Tibet
Prior Chinese research of substances within Tibetan glaciers indicated carbon from forest fires, crop burning and domestic cooking stoves from India have caused the melting. While these could be contributing factors, scientists say the global rise in temperatures is indisputably the primary cause. Tibetans say there has been a drastic change of temperature since 1980s. One U.S.-based Tibetan who recently returned to Lhasa expressed shock at seeing the climatological impact on people’s clothing style. “When I lived in Lhasa, it was very rare that people could walk outside in T-shirts,” said the man, who asked that his name be withheld. “Now people are walking in shorts!”
Tibetan Plateau in background of Himalayan range, viewed from flyover in Nepal.
National Geographic reported in 2010 that one glacier was retreating by about 300 meters a year, the length of a U.S. football field. As early as 2009, China’s leading scientist on glaciers, Qin Dahe, said glaciers on the Tibetan Plateau were melting faster than in any other part of the world. In the short term, he warned, the melt would trigger more flooding and mudslides; in the long term: "water supplies in the region will be in peril.” Some researchers have predicted that most of the Himalayan glaciers will be gone in 20 years.
Water needs
They compared pictures collected by a US reconnaissance programme with recent satellite data to measure the extent of glacial melt. They believe the now-declassified images could help to show how other remote regions have changed over time. The research was presented at the American Geophysical Union Fall meeting in San Francisco. “This imagery will be getting used more and more,” said Josh Maurer from Columbia University in New York. The images were taken by a United States spy satellite programme that went by the codename of Hexagon. During the 1970s and 1980s, it launched 20 huge reconnaissance satellites into space, which secretly snapped areas of interest below. The images were taken on rolls of film, which were then dropped by the satellites, and collected mid-air by passing military planes. The material collected was declassified in 2011 and is now being digitised by the US Geological Survey (USGS) for scientists to use.
The images were taken by the US Hexagon spy satellite programme
Among the spy images are pictures of the Himalayas, an area for which historical data is scarce. By comparing them with more recent satellite imagery from Nasa and Jaxa (Japanese Space Agency) scientists have been able to see how the region has changed. “What we are trying to do is to quantify by exactly how much are the glaciers retreating, how much ice are they losing and at what rate,” said Josh Maurer. “So we’ve used the images to extract 3D models of the terrain back in the 1970s. “We can see the height of the glacier ice in 1973, and we take those elevation models, and can take the difference between those and the modern day elevation models, and we can work out how the ice volume is changing over time.”
The researchers have found that the extent of the ice loss has been great. “At every point on the glacier surface across the whole of the Himalayas a quarter of a metre of water is being lost each year,” said Mr Maurer. “I wouldn’t say it’s surprising given the climate data we have, but it is very very interesting to see how much ice is lost. “And populations downstream where they depend on these water resources are going to be affected. “As the glaciers shrink and retreat, the amount of run-off they provide to these streams will increase in the short term as they melt, but over the next 100 years it will decrease more and more, and that’s going to have a negative impact on water resources.” He said that the images from the Hexagon programme are now being used by various research groups to track how other parts of the Earth have changed over time.
Spy satellites reveal Himalayan melt - BBC News
