In the northern backcountry of Denali National Park, a team from Northern Arizona University is drilling into frozen soil to study the aftermath of a 2013 lightning-sparked fire. Because the blaze crossed survey grids established by the National Park Service in 2001, researchers have a rare pre-fire snapshot of the landscape. Their measurements show that in the hottest-burned areas, the thawed layer above permafrost is now one to two feet deeper than in unburned plots—a sign that fire stripping away the insulating soil is driving rapid thaw.
The work is part of a broader effort to understand how Arctic-boreal fires, which are becoming more frequent and severe, feed back into climate change. Permafrost holds roughly 1.5 trillion tons of carbon, about twice the amount in the atmosphere. As it thaws, microbes release carbon dioxide and methane. Scientists have long debated whether the carbon uptake from "Arctic greening"—the spread of shrubs and trees as the region warms—could offset those losses. But recent observations, including this study, suggest that abrupt thawing and near-term emissions may overwhelm any eventual plant growth.
Researchers caution that large uncertainties remain, especially because many high-latitude fires occur in remote areas that have never been closely studied. Still, the Denali project offers concrete evidence that fire can dramatically deepen the active layer and accelerate permafrost loss. As one investigator put it, these are "huge biomes with massive fires that no one's ever been to or ever looked at," making direct field observations essential for refining climate projections.