News Release

Alsek River Mouth Predicted to Shift 20 Miles South of Current Location

Date: April 6, 2021
Contact: Peter Christian

On March 17, a peer-reviewed article in the scientific journal Geomorphology announced the results of research predicting that the Alsek River mouth is likely to shift 20 miles south from its current location in Glacier Bay National Preserve and possibly exit elsewhere from the park into the Gulf of Alaska.    

In the Geomorphology article, lead author NPS glaciologist Michael Loso and his co-authors conclude that due to warming caused by climate change Grand Plateau Glacier, which feeds the Alsek River and directs its flow, is receding at a rapid rate. “Glaciers are shrinking throughout Alaska’s national parks” said Loso, “but this situation is unusual because the glacier retreat is likely to shift the course of a major international waterway.” As the glacier continues to retreat, the flow of the Alsek River is likely to follow, eventually exiting the park into the Gulf of Alaska at a different location.  

The Alsek River originates in the St. Elias Mountain Range in Canada and flows through Glacier Bay National Park and Preserve before emptying into the Pacific Ocean at Dry Bay, Alaska. The name is of Tlingit origin and may mean "place where people rest." Managed by the National Park Service (NPS), the current mouth of the Alsek River is both a premier international river rafting end point and the site of a commercial fishery at Dry Bay.  

The physical and biotic environment of the area around the Alsek River is one of constant change characterized by rapid deglaciation since 1700. This glacial loss has now increased with climate change. The potential for rerouting of the river was recognized over a decade ago, but recent measurements of topography beneath the rapidly retreating ice have confirmed that this outcome is likely.   

If the mouth of the Alsek shifts as predicted from Glacier Bay National Preserve into the congressionally designated wilderness of Glacier Bay National Park, the outcome for the commercial fishery at Dry Bay is unclear. The fishery is already in decline due to isostatic rebound (lifting of the land following deglaciation), successional changes in the landscape, declines in salmon populations, and the difficulties presented by a shore-based fishery in a very remote location.     

For now, NPS scientists and managers are watching and studying the area. A change in the river’s flow and exit location could take years or happen quite swiftly depending on many variables. “An event like this is relatively rare and fascinating from a scientific perspective,” said Philip Hooge, superintendent for Glacier Bay National Park and Preserve. “The park is also keenly aware of how potentially concerning this must be for those whose livelihoods may be affected,” Hooge said.   Co-authors on the article are Christopher F. Larsen, Mark Fahnestock and Martin Truffer at the University of Alaska Fairbanks and Brandon S. Tober, Michael Christoffersen and John W. Holt at the University of Arizona, Tucson.