Three things you should know about permafrost
How much do you know about permafrost? Maybe, like me, you’ve been aware that this layer of frozen soil is thawing, that it’s important in the global puzzle of climate change … and that’s about the extent of it. The great news for both of us is that my colleague James Temple just published two….
Permafrost is a layer of soil that remains frozen for at least two consecutive years and covers about 15% of land in the Northern Hemisphere. Most of today’s permafrost formed during the last ice age, meaning some of it has been frozen for thousands of years. This frozen layer traps organic material like dead plants and animals, effectively locking away carbon that has been stored for centuries. However, as global temperatures rise, permafrost thaws, allowing microbes to break down this organic matter. This process releases greenhouse gases such as carbon dioxide and methane, which in turn accelerate climate change. Since 1850, the Arctic permafrost has shrunk by about 12%, with the rate of loss increasing over the last 50 years. Despite its significance, only a minority of climate models used in UN reports account for permafrost loss, and none include the rapid thawing triggered by events like heat waves or fires. This oversight suggests that current climate projections may underestimate the speed and scale of future warming.
Wildfires, a natural part of boreal forests, are becoming more intense due to climate change, and they play a key role in accelerating permafrost thaw. By the end of the century, fires could release the equivalent of 80 billion metric tons of carbon dioxide from thawing permafrost. Currently, policies in remote areas of Canada and Alaska often allow wildfires to burn if they do not threaten human settlements. However, some researchers argue that fighting these fires could help preserve the carbon stored in forests and permafrost beneath them. Scientists at the Woodwell Climate Research Center are developing a map to identify areas in Alaska where fires are most likely to spread and where permafrost is most vulnerable to releasing emissions. For example, Yedoma is a type of permafrost that is particularly deep and rich in carbon, formed during the late Pleistocene era. The challenge now is deciding how to respond, with suggestions including more controlled burns—practices used by Indigenous groups for millennia—or investing in early detection and rapid fire suppression to prevent large blazes.
Permafrost holds about 1.5 trillion tons of carbon, roughly twice the amount currently in the atmosphere. While thawing releases greenhouse gases and worsens climate change, the carbon cycle is far more complex than a simple loss of carbon. For instance, as temperatures rise, plants may gradually spread northward into areas where they previously could not grow. These plants absorb carbon dioxide from the atmosphere as they grow, partially offsetting the emissions released by thawing permafrost. Researchers are working to better understand this ecosystem, but the picture is increasingly complicated. The net effect on carbon levels depends on multiple factors, including the severity of fires, local climate conditions, the type of permafrost involved, and how the ecosystem recovers over time. As global temperatures continue to climb, these natural systems—many of which are still poorly understood—are increasingly disrupted, making long-term climate predictions even more challenging.
