The Mendenhall River in Alaska flooded in August 2023, not triggered by heavy rainfall, but by a glacial lake outburst flood (GLOF). Glacial lakes form in small side valleys that have lost ice and become dammed by the glacier in the main valley or dammed by left-behind rock and debris. Over time, as the ice-free basins fill with water, the lakes reach a breaking point where water pressure opens a drain under the glacier that releases water downstream, which can result in a GLOF. These events are unpredictable and have caused significant loss of life and infrastructure worldwide. Furthermore, it is unclear how these lake hazards may change as temperatures rise and glaciers continue to melt.  

Researchers from the Alaska CASC recently published an article in Nature Communications explaining how they used satellite imagery to study glacier-dammed lakes in Alaska. They found that 106 of 120 different lakes have drained at least one time since 1985. Although these lakes have drained 1,150 times over the study period, the researchers found no change in the frequency of these events. They also found that existing lakes now hold less water than they used to, which could lower flood hazards. However, accelerating glacier loss in Alaska could form more glacial-dammed lakes with thinner (weaker) ice dams. 

This Alaska CASC funded study is the first comprehensive assessment of ice-dammed lake drainage events and locations in Alaska, raising GLOF risk awareness. Additional monitoring could help resource managers further prepare as climate change transforms Alaska’s glacial landscapes. 

The original story from The Conversation was written by Alaska CASC Postdoctoral Fellow Brianna Rick. 

This work is supported by the Alaska CASC Project, “Assessing the Vulnerability of Alaska’s Glaciers in a Changing Climate”