How to study a swiftly melting climate disaster
Andrew Haverdink, a tall grad student in a rain bib and rubber boots, wrenched a double-handed drill from the frozen soil that underlies much of Alaska’s Denali National Park and then unclipped the hollow barrel from the end of the bit. He knelt in front of a blue tarp, lined the barrel up with a….
Permafrost is ground that remains frozen for at least two consecutive years, covering 15% of the Northern Hemisphere’s land surface. It holds about 1.5 trillion tons of carbon—roughly twice the amount currently in Earth’s atmosphere. Most of this carbon has been locked away for thousands of years, dating back to the last ice age. Permafrost forms in cold regions like Alaska, Canada, and Siberia, where temperatures stay below freezing for long periods. As global temperatures rise, permafrost thaws, releasing stored carbon in the form of greenhouse gases like carbon dioxide (CO₂) and methane (CH₄), both of which trap heat and accelerate climate change. The article highlights that permafrost loss is not uniform; some areas thaw gradually, while others experience abrupt thaw, where the ground collapses suddenly due to melting ice wedges, releasing carbon much faster than expected.
Wildfires in the Arctic-boreal region, such as the 2013 fire in Denali National Park, Alaska, are becoming more frequent and severe due to rising temperatures. These fires strip away vegetation that insulates the permafrost, exposing it to warmer air and deeper thawing. In the Denali fire, the thawed soil layer (active layer) extended up to two feet deeper than in unburned areas, accelerating permafrost melt. Fires also release stored carbon directly into the atmosphere. The 2007 Anaktuvuk River tundra fire in Alaska’s North Slope burned 400 square miles and released over 2 million tons of carbon—equivalent to the amount absorbed by global tundra ecosystems in an entire year. Researchers like Xanthe Walker and Michelle Mack study these fires to understand their long-term impact on carbon release and ecosystem recovery.
As permafrost thaws, it releases nutrients like nitrogen and phosphorus, which can promote plant growth in a phenomenon called Arctic greening. Warmer temperatures allow shrubs and trees with deeper roots to thrive in areas where they previously couldn’t survive. While this may seem beneficial, as plants absorb CO₂, the net effect on climate change is uncertain. Some studies suggest that increased plant growth could offset carbon losses from thawing permafrost, but newer research indicates that the carbon released from permafrost and fires may outweigh these gains in the short term. For example, a 2021 study found that severe burns in black spruce forests shifted the ecosystem toward faster-growing, less flammable deciduous trees, which stored five times more soil carbon than the original spruce stands. However, other cases, like the Anaktuvuk River fire, show that recovery can take decades or centuries.
Research teams, such as those from Northern Arizona University led by Michelle Mack and Ted Schuur, conduct field studies in Alaska to measure the impacts of fires and permafrost thaw. Their work involves drilling permafrost cores, setting up survey grids, and using tools like lidar flights and greenhouse-gas-measuring towers. In Denali National Park, researchers collected soil samples 13 years after a fire to analyze carbon loss and recovery. They found that in severely burned areas, the thawed soil layer remains deeper than before the fire, exposing more carbon to decomposition. Lab analyses of these samples aim to quantify how much carbon has been lost and whether ecosystems can recover. This hands-on research is critical because Arctic-boreal regions are vast and diverse, making remote sensing alone insufficient to capture the full picture.
To predict how permafrost will respond to future warming, Ted Schuur and his team conducted an experiment near Healy, Alaska, using snow fences to simulate the warmer temperatures expected in 20 to 30 years. By trapping extra snow, the fences insulated the ground during winter, keeping it warmer than control plots. Over 13 years, the soil carbon in these plots declined by 23%, and the land collapsed by several feet due to thawing permafrost. This subsidence creates craters and alters the landscape permanently. The experiment shows that even without fires, gradual warming can lead to significant carbon loss and ecosystem changes, highlighting the urgency of addressing climate change to prevent irreversible damage.
Despite advances in research, scientists face significant uncertainty about how permafrost thaw and fires will interact with climate change. Factors like local climate, fire severity, and permafrost type can lead to vastly different outcomes. For instance, some ecosystems may recover and store more carbon, while others could become permanent sources of greenhouse gases. Susan Natali of the Woodwell Climate Research Center estimates that about 40% of the Arctic-boreal region has already shifted from a carbon sink to a carbon source due to permafrost loss and fires. This means these areas now release more carbon than they absorb, accelerating global warming. Researchers emphasize that while the science is complex, the stakes are clear: permafrost carbon release could overwhelm other climate mitigation efforts if not addressed promptly.
