Millions of futures threatened by melting Himalayan glaciers

Dr Simon Cook, an expert in glaciology with the University’s Geography and Environmental Science department, says that climate change is accelerating the melt of glaciers in the region, circumstances he describes as “very concerning.”

He added that the rate of ice loss in recent decades was now ten times greater than the long-term average since the Little Ice Age, the last major period of glacier expansion that occurred 400-700 years ago.

The research, co-authored by Dr Cook and led by colleagues at the University of Leeds, forms part of a new paper published today in Scientific Reports.

Having mapped and reconstructed more than 14,000 glacier limits from the Little Ice Age period, the team calculated that the size of the glaciers had shrunk from a peak of 28,000 km² to around 19,600 km² today. Furthermore, over the same period the team found that the glaciers have lost between 390 km³ and 586 km³ of ice – the equivalent of all the ice contained today in the central European Alps, the Caucasus, and Scandinavia combined.

Dr Cook said, “In the modern era, satellite imagery has allowed us to track glacier change over recent decades. However, we have looked back a lot further and this has allowed us to gauge how severely these glaciers have retreated.

“The acceleration in glacier loss that we have witnessed has likely been prompted by climate change, the effects of which are very concerning for millions of people who depend on these glaciers and the rivers they feed.”

The Himalayan mountain range is home to the world’s third-largest amount of glacier ice, after Antarctica and the Arctic. Feeding into some of Asia’s major rivers, including the Brahmaputra and Ganges, melt from the glaciers is crucial in providing water for human consumption, irrigation and hydropower in this region.

The team used satellite images and digital elevation models to produce outlines of the glacier’s extent 400-700 years ago and to ‘reconstruct’ the former ice surfaces. The satellite images revealed sediment ridges called moraines that mark the former glacier boundaries and the researchers used the geometry of these moraine ridges to estimate the former glacier extent and ice surface elevation. Comparing the glacier reconstruction to the glacier now, determined the volume and hence mass loss between the Little Ice Age and now.

Dr Jonathan Carrivick, corresponding author and Deputy Head of the University of Leeds School of Geography, said, “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.”

The findings follow the recent COP26 climate summit in Glasgow, which emphasised the need for countries to unite in action to address our warming planet.

“Glacier melt is a normal process, and indeed desirable in terms of water supply,” added Dr Cook.

“But what is alarming is the rate at which this melt is now happening and that the glaciers are losing more mass than they are gaining through snowfall.

“While the outcomes of COP26 may ultimately be viewed as insufficient, we did see some positive moves and some important commitments were made by the international community. Glaciers are fragile and anything that we can do to slow down their recession should be welcomed, but there can be no doubt that we have long-term concerns about the future of these crucial water stores.”