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Melting Of Himalayan Glaciers May Be Slowed By Debris

January 25, 2011

A blanket of dust and rock debris is apparently shielding some glaciers in the world’s highest mountain range from thawing, and varying wind patterns might explain why some are defying a melt.

“Our study shows there is no uniform response of Himalayan glaciers to climate change and highlights the importance of debris cover,” scientists at universities in Germany and the United States wrote in the study of 286 glaciers.

Elsewhere in the Himalayas “more than 65 percent of the monsoon-influenced glaciers … are retreating,” they wrote in the journal Nature Geoscience of the satellite study from 2000 to 2008. Some glaciers that were stable in length were covered by a thick layer of rocky debris.

“Overall in the Himalayas, the glaciers are retreating,” Dirk Scherler, the lead author at the University of Potsdam in Germany, told Reuters. The findings underscore that experts in the United Nation’s Intergovernmental Panel on Climate Change (IPCC) were wrong to say in a 2007 report that Himalayan glaciers could vanish by 2035 in a headlong thaw, the panel corrected the error in 2010.

The report said that 58 percent of glaciers examined in the westerly Karakoram range of the Himalayas were stable or advancing, possibly influenced by cool westerly winds rather than monsoons from the Indian Ocean.

“The findings did not allow the experts to make any new estimates of water losses from Himalayan glaciers, whose seasonal melt helps keep up flows in the dry season in rivers from the Ganges to the Yangtze. More study was needed,” Scherler told Reuters.

“Glaciers are important to water supply to many people living in lowlands, not only for food and drinking water but also for hydropower. It’s essential to know what’s going on.” Scherler said.

Worldwide, most glaciers are shrinking from the Alps to the Andes in a trend blamed by the IPCC on greenhouse gases from human activities, led by the burning of fossil fuels. Debris in the Himalayas — darker than ice and so soaking up more of the sun’s energy — tended to quicken a thaw if it was less than 2 cms (0.8 inch) thick. But a thicker layer on some Himalayan glaciers acted as insulation, slowing the melt.

Image Caption: Crevasses of a steep glacier in the Sutlej Valley of the Western Himalaya. This glacier has a debris-covered toe. Credit: Bodo Bookhagen, UCSB

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