Alaska's Glacial Lakes Expanding, Increasing Outburst Flood Risk

Researchers warn that glacial lake growth in Alaska could lead to more destructive flooding downstream

Published on Mar. 10, 2026

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A new study from Colorado State University has found that Alaska's glacial lakes are expanding about 120% faster on average today than they were from 1986 to 1999, more than twice as fast. The researchers used satellite data and ice thickness measurements to map the growth of these lakes and found that they could become more than four times larger as glaciers continue to melt, increasing the potential for damaging glacial lake outburst floods.

Why it matters

Glacial lake outburst floods can have devastating impacts on downstream ecosystems and infrastructure, as seen in Alaska's capital city of Juneau where the Mendenhall River has experienced 15 straight years of increasingly large and destructive floods from the Suicide Basin glacial lake. This problem is not unique to Alaska, with more than 15 million people globally living in areas at risk of glacial lake outburst floods, particularly in the Himalayas and Andes regions.

The details

The researchers documented the evolution of 140 of the largest glacial lakes in Alaska between 2018 and 2024, finding that the fastest-growing lakes are those at the terminus of glaciers. By mapping the deep depressions, or glacial-bed overdeepenings, carved by glacial flow, the researchers were able to predict where new glacial lakes are likely to form and expand in the future. They found that existing glacial lakes in the region may ultimately expand fourfold, with one lake at the terminus of the Malaspina Glacier potentially growing to cover an additional 570 square miles.

  • Between 1985 and 2020, ice-dammed lakes in Alaska broke through their barriers and drained more than 1,150 times.
  • The researchers documented the evolution of 140 of the largest glacial lakes in Alaska between 2018 and 2024.

The players

Colorado State University

The university where the lead researcher, Dan McGrath, is an associate professor of cryospheric sciences.

Mendenhall River

A river in Juneau, Alaska that has experienced 15 straight years of increasingly large and destructive floods from the Suicide Basin glacial lake.

Suicide Basin

A small glacier-dammed lake 5 miles up the mountains from Juneau, Alaska that has been the source of destructive glacial lake outburst floods.

U.S. Army Corps of Engineers

The organization discussing an ambitious and expensive solution to create a permanent drain from Suicide Basin to prevent future outburst floods.

Malaspina Glacier

The largest glacier by area in southeast Alaska, with a glacial lake at its terminus that could expand to cover an additional 570 square miles.

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What’s next

The U.S. Army Corps of Engineers is discussing an ambitious and expensive solution to create a permanent drain from the Suicide Basin glacial lake to prevent future outburst floods, with initial cost estimates ranging from $613 million to $1 billion.

The takeaway

As glaciers continue to retreat due to climate change, the number and size of glacial lakes in Alaska and other regions around the world will continue to grow, posing an increasing risk of destructive outburst floods that can devastate downstream communities and ecosystems. Mapping and monitoring these expanding lakes is crucial to help prepare and mitigate the hazards.