Researchers in Denali are drilling permafrost cores to measure how a major tundra wildfire deepened seasonal thaw, risking carbon release and climate feedbacks.
In Alaska’s Denali National Park, graduate student Andrew Haverdink leaned into a two-hand drill, tugging a hollow corer from ground that has stayed frozen for millennia. Wearing rain gear and rubber boots, he pulled the barrel from the bit, lined it up over a tray on a blue tarp, and pressed a rod through the tube. Out slid an intact cylinder of dark, carbon-rich permafrost—at least a foot long—offering a rare, physical record of a landscape now changing fast.
Haverdink was working with a Northern Arizona University team on a tundra research plot marked by surveyor’s tape strung across tussocks, alder, and fireweed. Their focus is a fire that began with a lightning strike in late June 2013 in the park’s northern backcountry. Driven by Chinook winds—strong downslope gusts that form when moist ocean air crosses the Alaska Range and descends—the blaze swept through nearly 35,000 acres of mostly treeless terrain.
The fire didn’t just consume plants. In places, it burned into the upper soil, removing vegetation and the insulating organic layer that helps keep underlying permafrost frozen. That matters because permafrost is one of the planet’s largest carbon reservoirs, and it is widespread: about 85% of Alaska sits atop it.
When the researchers returned for their first major survey in 2016, they found signs of substantial post-fire thaw. In the most severely burned areas, the “active layer”—the surface soil that thaws each summer above permanently frozen ground—was between about one and nearly two feet deeper than in comparable sites outside the burn scar. A deeper active layer indicates more heat penetrating the soil and suggests accelerated permafrost degradation.
The Denali site offers an unusual scientific advantage. The 2013 fire crossed two established survey grids that the National Park Service had set up back in 2001, including the grid where the team collected cores. That pre-fire baseline gives researchers a “before-and-after” window into how wildfire reshapes vegetation, carbon dynamics, and permafrost over time, said project co-lead Xanthe Walker as she monitored the fieldwork.
Such direct measurements are increasingly important as scientists try to quantify how Arctic and boreal ecosystems respond to a warming world. High-latitude fires are happening more often and with greater intensity than in the past, and they can amplify climate change by speeding permafrost thaw. That thaw, in turn, can release greenhouse gases, creating feedback loops in which warming promotes fire, fire exposes and warms soils, and soils emit gases that drive further warming.
Researchers are still working to pin down how strong these cascading effects are and how they interact with other landscape changes. Earlier modeling suggested that, over long periods and under moderate warming, increased plant and tree growth could absorb enough carbon dioxide to offset much of the carbon released from warming soils and thawing permafrost. But the growing body of field observations and updated analyses is raising concerns about emissions in the coming decades—precisely the timeframe in which the world is trying to keep temperature rise within safer limits.
Permafrost underlies about 15% of the Northern Hemisphere’s land surface and stores roughly 1.5 trillion tons of carbon—about twice the amount currently in the atmosphere. Much of it formed during the last ice age, yet it has been thawing more quickly over the past half-century as temperatures rise and fires worsen. Once thawed, microbes can begin decomposing long-frozen organic matter, releasing carbon dioxide and methane, both potent greenhouse gases.
Why it matters
The Arctic-boreal region contains an enormous, vulnerable carbon stockpile, and wildfire is increasingly acting as a trigger that exposes it. Better measurements from places like Denali will shape how scientists project near-term climate risk and how policymakers plan for emissions pathways. What happens next—whether vegetation recovery can meaningfully counteract soil emissions, and how quickly fire regimes are changing—will influence climate targets worldwide.