Fire on Ice: The Arctic’s Changing Fire Regime

The number of wildfires in the Arctic is increasing, according to NASA researchers. Additionally, these fires are burning bigger, hotter and longer than in previous decades.

These trends are closely linked to the rapidly changing climate of the region. The Arctic is warming nearly four times faster than the global average, a change that directly impacts rain and snow in the region and decreases soil moisture, making the landscape more flammable. Lightning, the main source of ignition for fires in the Arctic, also occurs further north. These findings are detailed in a report published in 2025 by the Arctic Monitoring and Assessment Program (AMAP), a working group of the Arctic Council.

“Fire has always been a part of boreal and Arctic landscapes, but it is now starting to act in more extreme ways, mimicking what we have seen in temperate and tropical zones,” said Jessica McCarty, deputy chief of the Earth Sciences Division at NASA Ames Research Center and an expert on Arctic fires. McCarty, the lead author of the report, worked on an international team for AMAP.

But it’s not just the number of fires that worries scientists; that’s how hot they burn.

“It’s the intensity that worries us the most because it has the most profound impact on how ecosystems change,” said Tatiana Loboda, chair of the Department of Geographic Sciences at the University of Maryland.

The word “Arctic” often conjures up images of glaciers, snow and a frozen ocean. So how can such a place catch fire?

Officially, the Arctic refers to the region north of 66.5 degrees North, although many Arctic researchers study 60 degrees North and above. Although much of the region is covered in snow and ice, the Arctic is also home to a diverse range of ecosystems that change as they expand poleward.

It starts with boreal forests, which are primarily made up of conifers like spruce, fir, and pine. As these forests thin out northward, they give way to shrubs, then prairie tundra, and finally rocks, ice, and polar bears.

Much of the vegetation is covered with snow in winter, which melts in spring. Exposed, the vegetation dries in the sun. When presented with an ignition source like a lightning strike, it can quickly become fuel for a fire.

According to the AMAP 2025 report, an increasingly flammable landscape combined with more lightning strikes results in larger, more frequent and more intense fires than the landscape is suited to.

“There is variability from year to year, but over the decades we have on average about double the area burned in the North American Arctic compared to the mid-20th century,” said Brendan Rogers, senior scientist at the Woodwell Climate Research Center.

Low-intensity fires, which the Arctic is accustomed to, leave most of the forest standing, allowing the understory and upper soil layers to recover quickly.

In contrast, intense fires kill trees and can trigger a process called secondary succession, in which new species replace those that have died. These fires also burn deep into the carbon-rich soil, changing the region’s hydrology and accelerating snowmelt. Additionally, smoke and habitat damage from massive, burning fires pose significant health risks to human communities and local wildlife.

The mid-2010s marked the beginning of a new fire regime. For example, Greenland experienced significant wildfires in 2015, 2017, and 2019. Researchers also began observing fires occurring regularly in the Arctic as early as late March, much earlier in the year than historical records show, and burning well after the first snowfall. “It’s about how often these fires burn in the same place,” Loboda said. “Many areas are now burning two, three, even five times in a very short period of time. The impact is immense: it’s happening in the tundra and boreal regions, and these areas cannot recover.”

What makes Arctic ecosystems, and by extension Arctic fires, unique compared to much of the world is what happens underground: particularly in peat and permafrost.

The peat is old: thousands and thousands of years.

When glaciers retreated at the end of the last ice age, they left behind deposits of old trees, grasses and other organic matter that partially decomposed to form carbon-rich soil. Over time, layers of deposits built up into peat, which is now a main ingredient of Arctic soils.

When intense fires burn deep peat deposits, they can create a phenomenon called lingering fire, more commonly known as zombie fire, in which the remains of the fire remain alive throughout the winter. These fires appear extinguished on the surface, but continue to smolder underground during the winter, coming back to life when spring brings drier conditions.

Permafrost, ground frozen all year round, may be even older. Part of the permafrost predates the human species, Homo sapiensremaining continuously frozen for over 400,000 years. This age is what makes these frozen layers so important: they store ancient organic matter and the carbon it contains for millennia.

When organisms die and decompose, this process naturally releases carbon dioxide and methane. In the Arctic, permafrost keeps these organisms literally frozen, effectively freezing them over time.

NASA scientist and permafrost expert Clayton Elder describes observing this effect in the Permafrost Tunnel in Fairbanks, Alaska. “You can go into the tunnel and see grass embedded in the wall,” Elder said. “It’s still green, but when you carbon date it, it’s 40,000 years old.”

But as the Arctic warms, thaws and burns, carbon stored in peat and permafrost is released into the atmosphere. This is important, because what is locked beneath the surface is enormous. Together, Arctic peat and permafrost store twice as much carbon as the entire Earth’s atmosphere.

According to McCarty, this thaw will lead to global change.

“This is old ice, ice that is part of our hydrological system and forms a climate homeostasis that we grew up in as a species,” McCarty said. “There will be changes that we can’t predict: humanity hasn’t experienced the climate the planet is heading toward. It will be interesting to model; there are so many different ways this could evolve.”

To address Arctic challenges, scientists are discovering new applications of existing data and developing new technologies.

“NASA satellites are the real backbone of what we understand,” Rogers said. “These satellites have given us a 25-year record of wildfire data, which is invaluable. They are essential for our understanding of how these fire regimes are changing and for thinking through everything that is happening in the solutions space.”

New satellites and advances in artificial intelligence are advancing the understanding of ignition sources, fuel availability and flammability, and fire behavior. All of these data are important for monitoring fires and modeling future fire behavior, as well as assessing the vulnerability of boreal and Arctic ecosystems to increasing fire levels.

“One of our conclusions is that observations need to be more focused,” McCarty said. “We know some of what’s happening, but we need to better understand why and how to monitor these isolated areas. That means we’ll need satellites and field campaigns that think through this more complex fire landscape. What happens in the Arctic will impact the rest of the planet.”

Story by Milan Loiacono, NASA Ames Research Center.