Residents in Juneau, Alaska, are evacuating their homes as meltwater from the Mendenhall Glacier escapes a natural ice dam, raising concerns over potentially record-breaking flooding in the state capital.
The National Weather Service (NWS) in Juneau issued a flood warning as the glacial outburst water flows into the Mendenhall River, putting nearby homes at risk. Officials had warned residents for days that evacuations could become necessary, and on Tuesday, they confirmed that water had started spilling over the ice dam.
The glacier, a major tourist attraction, sits approximately 12 miles (19 km) from Juneau. Water levels reached 9.85 ft (3 m) on Tuesday—below the 14 ft threshold for major flooding—but by Wednesday morning, levels surged past 16 ft, marking a new crest. “This will be a new record, based on all of the information that we have,” said Nicole Ferrin, an NWS meteorologist, at a press conference.
Glacial lake outburst floods (GLOFs) occur when meltwater from snow, ice, and rain accumulates in a glacial lake and drains rapidly, similar to pulling the plug from a full bathtub. When the water overtops the glacier holding it back, sudden floods can occur.
Alaska Governor Mike Dunleavy declared a state disaster on Sunday, citing the “imminent threat of catastrophic flooding from a glacier lake outburst flood” in the Juneau area. Flooding has been a recurring threat in the region since 2011, with homes previously damaged or swept away; last year alone, hundreds of residences were affected.
Glaciers worldwide are shrinking due to rising temperatures, forming extra meltwater lakes that can grow in size and number. Natural ice and rock dams that hold these lakes in place can fail suddenly, triggering dangerous floods. Scientists warn that climate change is likely to increase the frequency of such outburst floods, though individual events are influenced by multiple factors.
