Glacial outburst floods aren't a new phenomenon in Alaska, but climate change is scrambling the geography of risk.

A huge basin of rainwater and snowmelt dammed by Alaska’s Mendenhall Glacier has started to release, sending a potentially record surge of flooding toward parts of Juneau.

In 2023, a glacier lake outburst at Mendenhall's Suicide Basin destroyed several structures along the Mendenhall River as the water rushed downstream. The record flooding prompted city officials in Juneau to issue an emergency declaration.