Thinning glaciers ‘endangering South Asian water supply’

The Naimona'nyi glacier is thinning, say scientists Copyright: Flickr/vijaykiran

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[NEW DELHI] New evidence that Himalayan glaciers are shrinking has added weight to concerns that there could be severe water shortages in the region by 2030.

Researchers drilling an ice core in the 6,050 metre-high Naimona’nyi glacier near Tibet were expecting to find radioactivity left by atomic tests carried out 50 years ago. Instead they found little more than background levels of radioactivity.

The scientists, from the Institute for Tibetan Plateau Research, the Chinese Academy of Sciences and the US-based Ohio State University, say that this is a sign that the glacier is thinning, with no accumulation of new ice since 1944.

Seasonal runoff from glaciers such as Naimona’nyi feeds the Indus, Ganges and Brahmaputra rivers in that part of the Asian subcontinent. The rivers are already severely depleted in places for months each year, say the researchers, writing in Geophysical Research Letters this month (November). The lack of new ice accumulating on the glaciers can only decrease river levels, they add.

Current models predicting river flow in the region have taken recent glacial retreat into account, say the researchers. But they have not considered that some glaciers are also thinning.

"If the thinning isn’t included, then whatever strategies people adopt in their efforts to adapt to reductions in river flow simply won’t work," says Natalie Kehrwald, a doctoral student at Ohio State University and lead author on the paper.

The news comes in the same month that a major report from the UN Environment Programme (UNEP) highlighted the role of ‘atmospheric brown clouds’ in melting the Hindu Kush-Himalaya-Tibetan glaciers, amongst other effects.

The vast brown clouds, caused by the burning of fossil fuels and biomass, are now thought to be warming these elevated regions with a strength equal to that of greenhouse gases, says the report. The clouds could also be depositing black carbon on the snow and ice, causing them to absorb, rather than reflect, solar radiation — and thus warm up.

The Chinese Academy of Sciences estimates that glaciers in the region have shrunk by five per cent since the 1950s.

Link to abstract in Geophysical Research Letters