Rainfall, melting permafrost change Interior Alaska stream systems
By Gracie Banister | UAF on Comments Off on Rainfall, melting permafrost change Interior Alaska stream systems
Photo by Neal Pastick Karen Jorgenson, left, helps Torre Jorgenson describe permafrost soils and site characteristics along the Hulahula River in 2013.
The aquatic chemistry and flow rates in Interior Alaska’s streams are shifting in response to thawing permafrost and increased rainfall, a new study reports.
The study authors found that groundwater makes up a greater portion of streamflow in areas with less permafrost.
The paper, published in the June 2025 issue of Water Resources Research, was co-authored by the father-daughter team of Torre and Karen Jorgenson. Torre is an adjunct faculty member at the University of Alaska Fairbanks, and Karen is a research staff member with the UAF Institute of Arctic Biology.
The research was conducted at sites managed by the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory on Fort Wainwright and the Bonanza Creek Long-Term Ecological Research program, including sampling areas on Eielson Air Force Base.
The study had the benefit of daily, multiyear data in five large catchment locations, Karen Jorgenson noted. All areas studied are within about 50 miles of Fairbanks.
Their work looked at the percentage of stream water that originated from water sources like groundwater and rainfall.
One key finding supports the team’s initial hypothesis: Watersheds with diminished permafrost showed greater groundwater contributions to streams.
That suggests permanent ice layers prevent groundwater from rising up into the streams, Karen Jorgenson said. In areas where the permafrost has thawed, more groundwater could enter the streams, she said.
However, another trend surprised them.
“We thought more rainwater would percolate down into the groundwater before reaching streams,” Karen said. “Instead, we saw a lot of direct rainwater input into the streams, showing how responsive they are to precipitation.”
“We saw that the influence of permafrost on stream flows was often obscured by the influence of the timing and magnitude of rainfall, due to the melting and changes in precipitation occurring simultaneously,” she added. “This complicates what we expect to happen in the streams in the future.”
Torre Jorgenson said the thawing of permafrost will impact local economies, river travel, salmon populations and more.
“Permafrost occupies about half, and in some places 60% of the landscape,” he said. “It is a huge current influence on ecosystem processes. We are expecting to lose all of this permafrost in the next 50 to 100 years, totally transforming portions of our landscape.”
In the meantime, he said, “it is really important to develop some kind of stream chemistry metrics to quantify shifts in the hydrologic pathways.”
Torre Jorgenson earned his master’s at UAF, was the first camp manager of Toolik Field Station in 1977 and received an honorary doctorate in 2017. In the study, he contributed his expertise in remote sensing and landscape ecology, and he created detailed permafrost maps of the stream catchments.
Karen Jorgenson grew up in Fairbanks but completed her college education in the Lower 48, obtaining her master’s degree at the University of Wyoming.
“I went from working on stream systems outside of Alaska to coming back home and working on stream systems in Alaska,” she said. “It’s fun to work in the same ecosystems as my father and where he made his career.”
Additional authors include Thomas Douglas of the Army Corps’ cold regions lab at Fort Wainwright, Neal Pastick with the U.S. Geological Survey in South Dakota and Tamara Harms with the University of California, Riverside.
The paper contributes to a broader research initiative led by principal investigator Qianlai Zhuang at Purdue University, who is developing a model to forecast and map environmental changes driven by climate change. The study’s findings provide data that will improve the model’s accuracy and practical application.
The Alaska team’s work, along with Zhuang’s, is part of an even larger effort — NASA’s Arctic-Boreal Vulnerability Experiment. Launched in 2015, ABoVE aims to understand societal impacts and ecological vulnerabilities and resiliency across northern regions as the environment experiences rapid change.
