Worldwide, there are approximately 200,000 to 275,000 glaciers containing 69% of the world’s fresh water. They are found on every continent except Australia and are found in significant concentrations in the Arctic, Alaska and Antarctica along with high mountain ranges such as the Himalayas and Andes.
But what happens when climate change causes all those glaciers to melt?In a study published in the journal Nature Communications, researchers from Sweden, the United States, Switzerland and Norway mapped what lies beneath all the planet’s glaciers and came to a shocking conclusion: When some of that ice disappears, Earth could gain 56,659 new lakes in areas that are currently completely frozen.
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 the United States, the University of Lausanne in Switzerland, and the University of Oslo in Norway, the team analyzed glaciers outside the large ice sheets of Greenland and Antarctica.They reconstructed the terrain beneath the glaciers using a 3D ice flow model called the Instructed Glacier Model, which was GPU-accelerated and deep learning. The idea was to understand what the Earth’s surface would look like if the glaciers disappeared. The process was complicated because the base of glaciers is not directly visible and can hide deep valleys, depressions, natural basins and areas where meltwater tends to accumulate.
The work also produced a dataset called Topography of Decomposed Earth, or TOPO-DE v1.0. According to Nature Communications, the goal was to create a virtually consistent global map of terrain currently hidden beneath glaciers. This map is designed with a resolution of between 100 and 400 metres, depending on the region, and allows the observation of typical glacial landforms, such as carved valleys, deep basins and areas where lakes may appear in the future.According to the study, direct observations of ice sheet rise exist in only about 2% of global glaciers. Therefore, the researchers needed to combine data on topography, ice thickness, flow velocity, and mass balance with measurements already available in international databases.
More than 50 thousand lakes in the future
The main conclusion of the study was the identification of 56,659 potential future lakes with an area of at least 0.05 square kilometres. According to the authors, these future lakes could occupy 40,647 square kilometers and store up to 3,138 cubic kilometers of water.
This volume equates to about 7 millimeters of sea level rise that would be temporarily retained in these natural reservoirs, rather than flowing directly into the oceans. In practice, this means that about 6% of the new ice-free land could be covered by lakes.
The same study compares this figure with the global average coverage of lakes on non-glacial lands, which is about 2%.
Mountainous regions of Asia are a cause for concern
The study highlights high-altitude Asia, a region that includes mountain ranges such as the Himalayas, Karakoram, Hindu Kush, Pamirs and Tian Shan, as one of the most sensitive regions.
Researchers have observed significant declines near glacier fronts in this region. This is important because lakes that form near the lower part of glaciers can accumulate in larger quantities and are close to populated valleys, roads, hydroelectric power plants, agricultural areas and villages.
Nature Communications itself notes that large depressions near glacial fronts in Asia’s high mountains indicate an increased risk of flash floods caused by glacial lake outbursts.
These events are known by the English acronym GLOF, which stands for Glacial Lake Outburst Flood. It occurs when a glacial lake suddenly drains, releasing a large amount of water, clay, ice and sediment down the valley.
15 million people are under threat
The research also indicated 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 the journal Nature Communications estimated that 15 million people worldwide are exposed to the potential effects of flash floods from glacial lakes. This work identified the Asian high mountains as the most exposed region.
According to the 2023 study, about 9.3 million people at risk live in this region. The research also indicated that more than half of the global exposed population is concentrated in just four countries: India, Pakistan, Peru, and China.Despite the warning, the lakes formed by retreating glaciers won’t be all bad. They could become freshwater reserves in areas where glaciers already act as natural “water reservoirs.” In mountainous regions, accumulating snow releases water during droughts and helps supply rivers, communities, agriculture and energy generation. New lakes can store water, create habitats, modify landscapes, and even open opportunities for hydroelectric power in some contexts.
