Wisconsin-sized Alaskan permafrost area is thawing at an accelerating rate
A region of Alaskan permafrost the size of Wisconsin is thawing at an accelerating rate, releasing ancient stores of carbon into rivers and the ocean in ways that could permanently alter both the Arctic environment and the global climate, according to new research from the University of Massachusetts Amherst.
The study, published in Global Biogeochemical Cycles, is the most detailed analysis of its kind. Led by geoscientist Michael Rawlins, the team examined 44 years of model data at one-kilometer grid resolution, revealing how dramatically runoff is increasing and how much previously frozen carbon is now flowing through northern Alaska’s rivers.
Perhaps the most striking finding is how far into the year the thawing now extends. The permafrost thaw season has stretched into September and even October, which is weeks longer than in the recent past.
The focus area is Alaska’s North Slope, a vast and ecologically critical landscape. Hundreds of rivers and streams there drain into the Beaufort Sea and the changes underway carry consequences far beyond the Arctic.
The region’s rivers already have an outsized impact, as they deliver 11% of the world’s river water to an ocean that contains just 1% of the world’s ocean volume, making the Arctic, which is one of the fastest-changing parts of the globe, incredibly sensitive to whatever is happening in the rivers and stream.
At the heart of the problem is what scientists call the “active layer” — the upper portion of permafrost that freezes and thaws on a seasonal cycle. That layer has been deepening in recent decades due to the warming climate, sending proportionally more groundwater into Arctic rivers.
As the active layer grows, it also unlocks massive quantities of organic carbon that have been locked in the frozen ground for tens of thousands of years. Some of that carbon, totalling more than 275 million tons, gets released as planet-warming carbon dioxide every year, which can create a vicious warming feedback loop.
Rawlins has spent 25 years developing the Permafrost Water Balance Model, which estimates snow accumulation and melt, active layer changes and other factors to reconstruct conditions in areas where direct measurements are scarce.
The new study represents a significant leap in resolution and scope, the first time anyone has captured such a wide area of the Arctic down to the kilometer scale and over such a long period: daily river flows and coastal exports simulated over 44 years, from 1980 to 2023. Running each model simulation requires a supercomputer working continuously for ten days.
