Across the globe, there are approximately 200,000 to 275,000 glaciers that hold 69% of the world’s fresh water. They are found in every continent except Australia and are in heavy concentrations in the Arctic, Alaska, and Antarctica along with high mountain ranges like the Himalayas and Andes. But what happens when climate change causes all these glaciers to melt?In a study published in Nature Communications, researchers from Sweden, US, Switzerland and Norway mapped what lies beneath all the glaciers on the planet and reached a shocking conclusion: when part of this ice disappears, Earth could gain 56,659 new lakes in areas currently completely frozen.
The hidden terrain
The idea was to understand what the Earth’s surface would look like if the glaciers disappeared.
Led by researchers from Uppsala University in Sweden, Carnegie Mellon University in US, University of Lausanne in Switzerland and University of Oslo in Norway, the team analysed glaciers outside the large ice sheets of Greenland and Antarctica.They reconstructed the topography beneath the glaciers using a three-dimensional ice flow model called Instructed Glacier Model, accelerated by GPU and deep learning. The idea was to understand what the Earth’s surface would look like if the glaciers disappeared. The process was complex since the base of glaciers is not directly visible and could be hiding deep valleys, depressions, natural basins and areas where meltwater tends to accumulate.The work also produced a dataset called Topography of a Deglaciated Earth, or TOPO-DE v1.0. According to Nature Communications, the goal was to create a physically consistent global map of the terrain currently hidden beneath the glaciers. This map was built with a resolution between 100 and 400 meters, depending on the region, and allows observation of typical glacial relief forms, such as carved valleys, deep basins, and areas where lakes may appear in the future.According to the study, direct observations of glacier bed elevation exist for only about 2% of global glaciers. Therefore, the researchers needed to combine data on relief, ice thickness, flow velocity, mass balance, and measurements already available in international databases.
More than 50,000 lakes in the future
The main conclusion of the study was the identification of 56,659 possible future lakes with a minimum area of 0.05 km square. According to the authors, these future lakes could occupy 40,647 km² and store up to 3,138 km³ of water. This volume is equivalent to about 7 millimetres of sea level rise that would be temporarily retained in these natural reservoirs, instead of flowing directly into the oceans. In practice, this means that about 6% of the new ice-free landscape could be covered by lakes. The study itself compares this number with the global average of lake coverage in non-glaciated lands, which is approximately 2%.
Mountainous regions of Asia are a cause of concern
The study highlights High Mountain Asia, a region that includes mountain ranges such as the Himalayas, Karakoram, Hindu Kush, Pamir and Tien Shan, as one of the most sensitive areas. Researchers observed large depressions near the glacier fronts in this region. This is important because lakes formed near the lowest part of the glaciers can accumulate larger volumes and be close to populated valleys, roads, hydroelectric plants, agricultural areas, and villages. Nature Communications itself states that large depressions near the glacial fronts in High Mountain Asia suggest an increased risk of sudden floods caused by glacial lake outbursts. These events are known by the English acronym GLOF, for Glacial Lake Outburst Flood. They occur when a glacial lake suddenly drains, releasing a large volume of water, mud, ice, and sediments down the valley.
15 million people under threat
The research also pointed out that more than half of the globally exposed population is concentrated in just four countries: India, Pakistan, Peru, and China.
Another study published in 2023 in Nature Communications estimated that 15 million people worldwide are exposed to the potential impacts of sudden floods from glacial lakes. This work identified High Mountain Asia as the region with the greatest exposure. According to the 2023 study, about 9.3 million exposed people live in this region. The research also pointed out that more than half of the globally exposed population is concentrated in just four countries: India, Pakistan, Peru, and China.Despite the warning, the lakes formed by the retreat of glaciers will not be all bad. They can become freshwater reserves in regions where glaciers already function as a king of natural “water tank.” In mountain areas, accumulated ice releases water during dry periods and helps supply rivers, communities, agriculture, and energy generation. New lakes can store water, create habitats, modify landscapes, and even open opportunities for hydroelectric use in some contexts.
