The accelerating melting of the Himalayan glaciers threatens the water supply of millions of people in Asia, new research warns.
Himalayan glaciers are shrinking
The University of Leeds has led a study investigating the rate the ice is melting at this Himalayan Mountain range. The scientists revealed that the glaciers have lost ice ten times more quickly over the last few decades than on average since the last major glacier expansion up to 700 years ago, which is a period known as the ‘Little Ice Age.’
Dr Johnathan Carrivick, corresponding author and Deputy Head of the University of Leeds’ School of Geography, and his team also discovered that the Himalayan glaciers are shrinking far more rapidly than glaciers in other parts of the world.
The scientists made a reconstruction of the size and surfaces of 14,798 Himalayan glaciers during the Little Ice Age. This allowed Carrivick and his team to calculate that the glaciers have lost around 40% of their area, shrinking from a peak of 28,000 km2, to around 19,600 km2 today.
During that period, between 390 km3 and 586 km3 of ice has been lost by the Himalayan glaciers presently, which is equivalent to all of the ice contained today in the central European Alps, the Caucasus, and Scandinavia combined. The water lost through this process has resulted in sea levels across the world raising by up to 1.38mm.
“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,” said Carrivick.
Concerns for Asia
The Himalayan Mountain range is home to the world’s third largest amount of glacier ice– after Antarctica and the Arctic– and is often referred to as ‘the Third Pole.’ The accelerated rate of the Himalayan glaciers means significant implications for the hundreds of millions of people who depend on Asia’s river systems for food and energy. These rivers include the Brahmaputra, Ganges and Indus.
The researchers used satellite images and digital elevation models to produce outlines of the glaciers’ extent 400 to 700 years ago and to reconstruct the ice surface. The satellite images revealed ridges that mark the former glacier boundaries. Carrivick and his team used the geometry of these ridges to estimate the former glacier extent and ice surface elevation. By comparing the glacier reconstruction to the glacier now, the scientists were able to determine the volume and mark loss between the Little Ice Age and now.
When scientists considered the eastern regions, with east Nepal and Bhutan marking the north of the main divide, it was noted that the Himalayan glaciers are generally losing mass faster in the eastern regions. The study suggests that this variation is potentially due to differences in geographical features on the two sides of the Himalayan Mountain range and their interaction with the atmosphere, which resulted in different weather patterns.
Co-author Dr Simon Cook, Senior Lecturer in Geography and Environmental Science at the University of Dundee, 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.”
Himalayan glaciers are also declining faster where they end in lakes as opposed to land, which is resulting in several warming impacts. The number and size of these lakes are increasing so continued acceleration in mass loss can be expected. Similarly, glaciers which have significant amounts of natural debris upon their surfaces are also losing mass more quickly: they contributed around 46.5% of total volume loss despite making up only around 7.5% 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,” said Carrivick.