Subglacial landscape reveal potential future glacial lakes in the Southern Andes
This study presents the first regional reconstruction of subglacial topography in the Southern Andes, revealing that the region's retreating glaciers will leave behind over 3,900 potential future lakes capable of storing nearly 300 km³ of water, with significant implications for future freshwater resources and outburst flood hazards.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
As mountain glaciers retreat under a warming climate, they leave behind the land they once covered. This exposed ground is not always flat; centuries of moving ice have carved deep hollows and basins into the bedrock, much like a river carving a canyon. When the ice disappears, these hollows can fill with meltwater, creating new lakes. This transformation is not just a change in scenery; it reshapes how water flows through mountain regions, alters the risk of sudden floods, and changes the amount of water that eventually reaches the ocean. For communities living downstream, understanding where these future lakes will form and how much water they can hold is a matter of safety and survival.
A team of researchers has now mapped the hidden landscape beneath the glaciers of the Southern Andes, a massive mountain chain stretching from the arid north of Chile down to the southern tip of South America. By combining satellite images of the current ice with new, detailed radar measurements taken from the ground, they have reconstructed the shape of the bedrock hidden beneath thousands of glaciers. Their work reveals a vast, unseen topography that will soon be exposed as the ice melts away. The study provides the first regional picture of where these future lakes will appear and estimates how much water they will be able to store.
The researchers found that the Southern Andes hold a total ice volume of roughly 5,961 cubic kilometers. If all this ice were to melt and flow into the ocean, it would raise global sea levels by about 14.8 millimeters. However, the story does not end with the ocean. As the ice retreats, it will uncover 3,951 distinct depressions in the bedrock capable of becoming lakes. These future lakes have the potential to store nearly 299 cubic kilometers of water. This is a significant amount, representing about 5 percent of the region's total ice volume. In fact, this interception rate is unusually high compared to other mountain ranges around the world, where future lakes typically hold a much smaller fraction of the melting ice.
The distribution of these future lakes is far from even. The vast majority are located in the southern part of the range, specifically within the three great icefields of Patagonia. These three massive ice bodies contain more than 97 percent of the region's total ice and hold nearly all of the potential lake volume. In contrast, the drier, northern sections of the Andes, where glaciers are smaller and sit at higher elevations, will form far fewer lakes. Yet, in these northern regions, even a small amount of new water storage could be critical. The Central Andes, home to the city of Santiago and its seven million residents, relies heavily on glacier melt for its water supply. The study shows that the hollows exposed in this area could hold enough water to rival the capacity of existing major reservoirs, offering a potential buffer against the severe droughts that have recently plagued the region.
To create this map, the scientists did not simply guess at the shape of the ground beneath the ice. They used a method based on the physical properties of how ice flows. Ice behaves like a plastic material that deforms when the stress of its own weight becomes too great. By measuring the slope of the glacier's surface and calibrating their model with hundreds of kilometers of new radar data collected from 48 different glaciers, the team could calculate the thickness of the ice with greater accuracy than ever before. They also used information about where glaciers have already retreated to infer the shape of the bedrock near the edges of the remaining ice. This approach allowed them to produce a detailed map of the subglacial landscape, which they then used to identify every depression deep enough to hold water.
The results confirm that the Southern Andes are a global hotspot for the formation of future glacial lakes. The researchers estimate that these lakes will store about 298.6 cubic kilometers of water. While most of this volume is concentrated in the deep, heavily eroded basins of Patagonia, the smaller lakes in the north hold strategic value for water security. The study also highlights the dangers associated with these new lakes. When a glacier ends in a deep lake, the water can accelerate the melting and breaking of the ice, leading to rapid retreat. Furthermore, these lakes can burst their natural dams, causing catastrophic floods. The new maps identify exactly where these deep basins lie, allowing scientists and planners to anticipate where such hazards are most likely to develop.
This inventory is not a prediction of when these lakes will form, but rather a map of their maximum potential size once the ice has completely vanished. The actual volume of water in these lakes will depend on how much sediment fills them over time and how quickly the glaciers retreat. Nevertheless, the map provides a physical foundation for understanding the future of water resources and natural hazards in the Andes. By revealing the hidden landscape beneath the ice, the study offers a clear view of the water towers that will emerge as the glaciers disappear, helping communities prepare for a changing hydrological future.
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