NASA is keeping a space-based eye on the Himalayas, Karakoram, Hindu Kush –The glaciers and snowpack of Asia’s three high mountain ranges harbor the largest volume of freshwater outside the polar ice sheets, leading hydrologists to dubb this region The Third Pole. One-seventh of the world’s population depends on rivers flowing from these mountains for water to drink and to irrigate crops.
Rapid changes in the region’s climate, however, are affecting glacier melt and snowmelt. People in the region are already modifying their land-use practices in response to the changing water supply, and the region’s ecology is transforming. Future changes are likely to influence food and water security in India, Pakistan, China and other nations.
NASA is watching changes like these worldwide to better understand the future of our planet’s water cycle. In this region where there are extreme challenges in collecting observations on the ground, NASA’s satellite and other resources can produce substantial benefits to climate science and local decision makers tasked with managing an already-scarce resource.
The most comprehensive survey ever made of snow, ice and water in these mountains and how they are changing is now underway. NASA’s High Mountain Asia Team (HiMAT), led by Anthony Arendt of the University of Washington in Seattle, is in its third year. The project consists of 13 coordinated research groups studying three decades of data on this region in three broad areas: weather and climate; ice and snow; and downstream hazards and impacts.
All three of these subject areas are changing, starting with climate. Warming air and alterations in monsoon patterns affect the regional water cycle – how much snow and rain falls, and how and when the snowpack and glaciers melt. Changes in the water cycle raise or lower the risk of local hazards such as landslides and flooding, and have broad impacts on water allocation and crops that can be grown.
Making Impossible Science Possible
For most of human history, a detailed scientific study of these mountains was impossible. The mountains are too high and steep, and the weather too dangerous. The satellite era has given us the first opportunity to observe and measure snow and ice cover safely in places where no human has ever set foot.
“The explosive growth of satellite technology has been incredible for this region,” said Jeffrey Kargel, a senior scientist at the Planetary Science Institute in Tucson, Arizona, discoverer of ancient glaciation on Mars and leader of a HiMAT team studying glacial lakes. “We can do things now that we couldn’t do ten years ago – and ten years ago we did things we couldn’t do before that.” Kargel also credited advances in computer technology that have enabled far more researchers to undertake large data-processing efforts, which are required to improve weather forecasting over such complex topography.
Arendt’s HiMAT team is charged with integrating the many, varied types of satellite observations and existing numerical models to create an authoritative estimate of the water budget of this region and a set of products local policy makers can use in planning for a changing water supply. A number of data sets by HiMAT teams have already been uploaded to NASA’s Distributed Active Archive Center at the National Snow and Ice Data Center. Collectively, the suite of new products is called the Glacier and Snow Melt (GMELT) Toolbox.
Debris Dam Dangers and Other Impacts
There’s some urgency in completing the toolbox, because changes in melt patterns appear to be increasing the region’s hazards – some of which are found only in this kind of terrain, such as debris dam “failures” on glacial lakes and surging glaciers blocking access to mountain villages and pastures. In the last few decades, towns and infrastructure such as roads and bridges have been wiped out by these events.
Kargel’s team is studying catastrophic flooding from glacial lakes. These lakes start as melt pools on the surfaces of glaciers, but under the right conditions they may continue to melt all the way to ground level, pooling behind a precarious pile of ice and debris that was originally the front end of the glacier. An earthquake, rockfall or simply the increasing weight of water may breach the debris dam and create a flash flood.
Lakes like this were almost unknown 50 or 60 years ago, but as most high mountain Asian glaciers have been shrinking and retreating, glacial lakes have been proliferating and growing. The largest one Kargel has measured, Lower Barun in Nepal, is 673 feet (205 meters) deep with a volume of almost 30 billion gallons (112 million cubic meters), or about 45,000 Olympic-sized swimming pools full. The HiMAT team has mapped every glacial lake larger than about 1,100 feet (330 meters) in diameter for three different time periods – about 1985, 2001 and 2015 – to study how the lakes have evolved.