Alaska permafrost thaw suggests lasting landscape change

A 44-year modeling study led by Michael Rawlins finds that thawing permafrost on Alaska’s North Slope is lengthening the active thaw season into September and October and increasing freshwater and dissolved organic carbon delivered to coastal estuaries.

Researchers report that parts of northern Alaska are showing signs of lasting environmental change as rising temperatures thaw permafrost beneath the Arctic landscape. The finding comes from a new study led by geoscientist Michael Rawlins of the University of Massachusetts Amherst that used a high-resolution land model to examine runoff, groundwater flow and dissolved organic carbon moving from thawing ground into rivers. The team focused on a Wisconsin-sized area of the North Slope that drains to the Beaufort Sea and ran the model over a 44-year period from 1980 to 2023. Because direct observations in the region are sparse, the study relied on the Permafrost Water Balance Model to estimate changes across the landscape. Key findings: - The study modeled daily river flows and coastal exports from 1980–2023 at a one-kilometer resolution across the Alaskan North Slope. - Runoff and permafrost thaw increased across the region, with the active thaw season extending into September and October. - Dissolved organic carbon (DOC) inputs to rivers and coastal estuaries rose, with the largest increases in flatter northwest Alaska where older organic matter is abundant. - Researchers are now investigating how thawing ice-wedge polygons may further alter water and carbon pathways to coastal areas. Summary: The study indicates that a longer thaw season is increasing freshwater and organic carbon exports from the North Slope to coastal estuaries, with the greatest carbon increases identified in northwest Alaska. These changes are reported as likely to affect coastal salinity, chemistry and food web relationships. Researchers say further work is underway to assess how thawing ice-wedge patterns will change land-to-ocean connections and coastal ecosystem responses.