New research led by the University of Leeds has found that, during recent decades, Himalayan glaciers have lost ice ten times faster than on average since the last major glacial expansion known as the Little Ice Age (400-700 years ago). Moreover, they seem to shrink far more rapidly than glaciers in other parts of the world. The accelerating melting of these glaciers threatens the water supply of millions of people in Asia.
By using satellite images and digital elevation models, the scientists have reconstructed 14,798 Himalayan glaciers during the Little Ice Age and calculated that these glaciers have lost around 40 percent of their area, shrinking from a maximum of 28,000 km2 to around 19,600 km2 today.
During that period, the glaciers have also lost 390 km3 and 586 km3 of ice, which is the equivalent of all the ice contained today in Scandinavia, the European Alps, and the Caucasus. The researchers estimate that this ice loss may have raised the sea levels all over the world by 0.92 mm to 1.38 mm.
“Our findings clearly show that ice is now being lost from Himalayan glaciers at a rate that is at least ten times higher than the average rate over past centuries. This acceleration in the rate of loss has only emerged within the last few decades, and coincides with human-induced climate change,” explained study corresponding author Dr. Jonathan Carrivick, a professor of Geography at the University of Leeds.
Currently, the glaciers are losing mass faster in the eastern regions (with Nepal and Bhutan as a dividing line). This variation is probably caused by differences in geographical features on the two sides of this mountain range and their interaction with atmospheric processes.
Moreover, glaciers with significant amounts of natural debris on their surfaces are also melting faster, contributing around 46.5 percent of total volume loss, although they make up just 7.5 percent of the total number of glaciers.
“While we must act urgently to reduce and mitigate the impact of human-made climate change on the glaciers and meltwater-fed rivers, the modelling of that impact on glaciers must also take account of the role of factors such as lakes and debris,” Dr. Carrivick said.
“People in the region are already seeing changes that are beyond anything witnessed for centuries. This research is just the latest confirmation that those changes are accelerating and that they will have a significant impact on entire nations and regions,” added study co-author Simon Cook, a senior lecturer in Geography and Environmental Sciences at the University of Dundee.
The study is published in the journal Scientific Reports.