Climate: Melting Himalayan glaciers threaten farms

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A NASA Earth Observatory image shows the high peaks of the snow-capped Himalaya Mountains.

New study documents pace of ice loss in world’s tallest mountain

By Summit Voice

FRISCO — Melting Himalyan glaciers may not be causing a direct rise in sea level, but in some cases, the water is causing lakes overflow, flooding valuable agricultural land.

Glaciers are important indicators of climate change. Global warming causes mountain glaciers to melt, which, apart from the shrinking of the Greenlandic and Antarctic ice sheets, is regarded as one of the main causes of the present global sea-level rise.

Tibet’s glaciers have been losing mass at the rate of about 16 gigatons per year for the past decade. That loss is spread across about 80 percent of Tibet’s glaciers, according to Tobias Bolch, a glaciologist from the University of Zurich. That’s more than four times the volume of water in Lake Zurich and around six percent of the total loss in mass of all the glaciers on Earth.

But a few glaciers in the central and north-western part of the Tibetan Plateau have actually grown in mass. While the glaciers in the monsoon-influenced southern and eastern part of the plateau have melted significantly, the scientists recorded a neutral or even slightly positive result in the continental central and north-western area of the country.

“On average, the entire region is clearly characterized by a loss in mass,” Bolch said.

About two gigatons of the melted ice flows into lakes that have no outlet, causing them to burst their banks.

“In many regions, this means that valuable pasture areas become submerged,” Bolch said.

Stretching over an area of around 40,000 square kilometers, the Tibetan Plateau’s glaciers account for over a third of High Asia’s ice cover and are about twenty times the size of the ice surface of the Alps.

For their study, the international team of researchers evaluated satellite-based laser measurements of the glacier surfaces on the Tibetan Plateau between 2003 and 2009.

“Thanks to these measurements, we were able to gauge the temporal changes of the glacier heights and – combined with a detailed glacier inventory – changes in mass of the glaciers in Tibet, which are extremely difficult to access,” said Tubingen scientists Niklas Neckel and Jan Kropacek.

The results now published in Environmental Research Letters seem to contradict the data from a satellite mission based on other measuring methods, which indicates a slight increase in mass in the glacier ice for an almost identical period of time.

For Bolch, the different measurement values depend on the amounts of meltwater that remain on the plateau and do not flow away into the sea – and which his team has now managed to measure accurately for the first time. He attributes the data from the other studies that points to glacial growth more to other influences on the calculations – such as an increase in rainfall.

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