permafrost Archives - Woodwell Climate

In the northern ecosystems of the Alaskan boreal forest and tundra, wildfire is a natural – and even necessary – process. But as temperatures rapidly warm, wildfire frequency and severity in the state are breaking historical records.

Scientists at Woodwell Climate Research Center are studying the effects of these increased fires on the ecosystem. In a study published earlier this year, a research team led by Research Scientist Dr. Scott Zolkos examined the relationship between northern wildfires and one concerning byproduct of them: mercury pollution.

Higher temperatures, more wildfires, more pollution

In the last 25 years, Alaska has experienced some of the worst fire seasons on record. One of the reasons behind this is that climate change is hitting the north harder than other regions.

Northern latitudes, including the Arctic and boreal regions, are warming three to four times faster than the rest of the planet. As warmer temperatures melt snow earlier in the year and dry out soil and vegetation, the fire season lengthens and intensifies. According to Woodwell scientists, 2024 was the second-highest year for wildfire emissions north of the Arctic Circle.

“It’s really sort of a new phenomenon, the level of burning we’re seeing in the tundra,” Dr. Brendan Rogers, Senior Scientist, says.

Increasing fires means increasing air, water, and ecosystem pollution from the byproducts of burning vegetation and soils. Mercury is a toxic pollutant in wildfire smoke, but there is sparse research on mercury release from northern peatland wildfires which means scientists don’t yet have a great understanding of how increasing northern wildfire activity could counteract efforts to curtail human-caused mercury release. To understand these impacts, Zolkos and collaborators studied areas of the Yukon-Kuskokwim (YK) Delta in southwestern Alaska— a peatland environment that burned in 2015. The summer of 2015 made history as one of Alaska’s worst fire seasons, with over 5 million acres of land burned.

The research team used peatland soil samples that were collected between 2016 and 2018 by undergraduate participants of The Polaris Project to measure mercury. They then used the new mercury data together with organic carbon and burn depth measurements from another recent study to develop models that predicted mercury emissions from the 2015 wildfires.

Measuring mercury release

Mercury continuously cycles through the environment in air, water and soil, often changing between liquid and gaseous forms. It enters the atmosphere as emissions from human activities like the burning of fossil fuels and natural processes like wildfires and volcanoes. High levels of mercury can accumulate in the ground when vegetation takes up mercury from the atmosphere, then decomposes and deposits it into the soil. In northern peatlands, mercury has been accumulating with organic matter for thousands of years.

Mercury emissions occur when wildfire burns organic matter in soil and releases mercury that is bound to it back into the atmosphere. With increased temperatures and wildfire activity, the stabilization accumulation of mercury in the soil is threatened – and so is air quality.

“There are huge mercury stores in northern peatlands,” Zolkos says. “If peatlands burn more, it could potentially offset global efforts to reduce human mercury release into the environment.”

Zolkos and collaborators found that levels of mercury in peat in the YK Delta were similar to those in peatlands elsewhere in the north. Using an atmospheric chemical transport model developed by collaborators, the researchers also found that mercury deposition within 10 kilometers of wildfire sites was two times higher than normal, even though the majority of emissions from the fire traveled beyond Alaska.

With this information, Zolkos believes that increasing fire activity has the potential to unlock large amounts of soil-bound mercury in the North. The challenge now is figuring out exactly how much mercury is being released and where it ends up.

As a step to understanding this, Zolkos is leading a pilot project to develop an atmospheric mercury monitoring network across wildfire-susceptible peatlands in Alaska and Canada. Twenty-six air samplers, which collect mercury molecules in the air, were deployed at seven sites in Arctic-boreal peatlands across Alaska and Canada during the summers of 2024 and 2025. After the 2025 summer season is complete, the samplers will be sent to a lab at Harvard University, where Zolkos will measure their mercury content.

“Our goal is to work with collaborators to deploy these simple and cost-effective samplers that capture mercury in the atmosphere,” Zolkos says. “And from that, we can back-calculate the concentration of mercury in the air to understand wildfire impacts.”

By studying trends, Zolkos can compare levels of mercury in the air in areas affected and not affected by wildfire. And with added contextual data, scientists can model how much mercury might have been released from the soil and vegetation by wildfire.

Understanding wildfire impacts on air quality

In addition to containing mercury, wildfire smoke also emits particulate matter (PM2.5). PM2.5 refers to particles that are smaller than 2.5 micrometers in diameter – thirty times smaller than the average human hair. When breathed in, they can affect the heart and lungs and cause a variety of health problems, including aggravated asthma, decreased lung function, and increased respiratory symptoms.

Together with collaborators from the Permafrost Pathways project, Zolkos is also collaborating with Alaska Native communities to install PurpleAir sensors, a system of particulate matter monitors, to support tribally-led wildfire air pollution monitoring. This project helps to address monitoring needs in Alaska, where nearly 90% of rural communities reached or exceeded unhealthy levels of PM2.5 at least once due to wildfire in the last two decades.

“It’s a really great opportunity to work together with Alaskan Native communities and also to share knowledge, learn from them, and try and help them with any needs that they have for environmental monitoring,” Zolkos says.

So far, particulate matter sensors have been deployed in Pond Inlet in Nunavut, Canada, Churchill in Manitoba, Canada, and Akiachak, Alaska.

“The complex impacts of wildfire on Arctic and global communities is not something that can be solved by taking a measurement and seeing a number alone. These climate health impacts require a more holistic way of thinking and doing research” Dr. Sue Natali, Senior Scientist and lead of the Permafrost Pathways project, says. “What gives me hope is that the Western scientific community is now listening and hearing more from Indigenous partners to co-produce research to support climate resilient communities,”

When I started at Woodwell Climate, I had very little personal or professional experience with boreal wildfire. I was a forest ecologist drawn to this space by the urgency of the climate crisis and the understanding that northern ecosystems are some of the most threatened and critical to protect from a global perspective. More severe and frequent wildfires from extreme warming are burning deeper into the soil, releasing ancient carbon and accelerating permafrost thaw. Still largely unaccounted for in global climate models, these carbon emissions from wildfire and wildfire-induced permafrost thaw could eat up as much as 10% of the remaining global carbon budget. More boreal wildfire means greater impacts of climate change, which means more boreal wildfire. But when I joined the boreal fire management team at Woodwell, the global picture was the extent of my perspective.

This past June, under a haze of wildfire smoke with visible fires burning across the landscape, Woodwell Climate’s fire management team made our way back to Fort Yukon, Alaska. Situated in Yukon Flats National Wildlife Refuge at the confluence of the Yukon and Porcupine Rivers, this region is home to Gwich’in Athabascan people who have been living and stewarding fire on these lands for millennia. Our time there was brief, but it was enough to leave us humbled by the reality that the heart of the wildfire story—both the impacts and the solutions—lie in communities like Fort Yukon.

We listened to community members and elders tell stories about fire, water, plants, and animals, all of which centered around observations of profound change over the past generation. As we shared fire history maps at the Gwichyaa Zhee Giwch’in tribal government office, we were gently reminded that their knowledge of changing wildfire patterns long preceded scientists like us bringing western data to their village. We learned that fire’s impact on critical ecosystems also affects culture, economic stability, subsistence, and traditional ways of life. Increasing smoke exposure threatens the health of community members, particularly elders, and makes the subsistence lifestyle harder and more dangerous. A spin on the phrase “wildland urban interface,” Woodwell’s Senior Arctic Lead Edward Alexander coined the phrase “wildland cultural interface,” which brilliantly captures the reality that these fire-prone landscapes, culture, and community are intertwined in tangible and emotional ways for the Gwich’in people.

“There’s too much fire now” was a common phrase we heard from people in Fort Yukon. Jimmy Fox, the former Yukon Flats National Wildlife Refuge (YFNWR) manager had been hearing this from community members for a long time, along with deep concerns about the loss of “yedoma” permafrost, a type of vulnerable permafrost with high ice and carbon content widespread throughout the Yukon Flats. With the idea originating from a sharing circle with Gwich’in Council International, in 2023 Jimmy enacted a pilot project to enhance the fire suppression policy of 1.6 million acres of yedoma land on the Yukon Flats to explicitly protect carbon and climate, the first of its kind in fire management policy. He was motivated by both the massive amount of carbon at risk of being emitted by wildfire and the increasing threats to this “wildland cultural interface” for communities on the Yukon Flats.

Ever since I met Jimmy, I have been impressed by his determination to use his agency to enact powerful climate solutions. Jimmy was also inspired by a presentation from my postdoctoral predecessor, Dr. Carly Phillips, who spoke to the fire management community about her research showing that fire suppression could be a cost-efficient way to keep these massive, ancient stores of carbon in the ground. Our current research is now focused on expanding this analysis to explicitly quantify the carbon that would be saved by targeted, early-action fire suppression strategies on yedoma permafrost landscapes. This pilot project continues to show the fire management community that boreal fire suppression, if done with intention and proper input from local communities, can be a climate solution that meets the urgency of this moment.

“Suppression” can be a contentious word in fire management spaces. Over-suppression has led to fuel build up and increased flammability in the lower 48. But these northern boreal forests in Alaska and Canada are different. These forests do not have the same history of over-suppression, and current research suggests that the impacts of climate change are the overwhelming driver of increased fire frequency and severity. That said, fire is still a natural and important process for boreal forests. The goal with using fire suppression as a climate solution is never to eliminate fire from the landscape, but rather bring fires back to historical or pre-climate change levels. And perhaps most importantly, suppression is only one piece of the solution. The ultimate vision is for a diverse set of fire management strategies, with a particular focus on the revitalization of Indigenous fire stewardship and cultural burning, to cultivate a healthier relationship between fire and the landscape.

The boreal wildfire problem is dire from the global to local level. But as I have participated in socializing this work to scientists, managers, and community leaders over the past year, from Fort Yukon, Alaska to Capitol Hill, I see growing enthusiasm for solutions that is not as widely publicized as the crisis itself. I see a vision of Woodwell Climate contributing to a transformation in boreal fire management that has already begun in Indigenous communities, one that integrates Indigenous knowledge and community-centered values with rigorous science, and ends with real reductions in global carbon emissions. Let’s begin.

As the Arctic heats up three to four times faster than the rest of Earth, hotter temperatures have super-charged northern fires, causing them to burn more area, more frequently, and more intensely.

These fires have a range of harmful impacts on communities, ecosystems, and wildlife in the north. When it comes to carbon, they represent a unique now-and-future threat to global climate. That’s because much of the boreal forest, which circles the high northern latitudes, is underlain by carbon-rich frozen ground called permafrost. Stocked with carbon from dead animal and plant matter that’s accumulated over hundreds to thousands of years, permafrost functions as Earth’s “deep freezer,” keeping the planet cool by keeping carbon out of the atmosphere.

When permafrost thaws, microbes begin to access and break down the once-frozen carbon, releasing it to the atmosphere where it contributes to warming. Wildfires accelerate this process by burning off the organic soil layer that protects permafrost— opening the door on the freezer. And as temperatures in the north rise and boreal forests dry out and experience greater climate stress, the fires these forests evolved with have become more frequent and severe, with consequences for both permafrost and our climate.

Why are boreal forests important to climate?

The boreal forest, the largest forested biome on Earth, covers large stretches of North America, Europe, and Russia and stores 25% of the planet’s terrestrial carbon. Roughly 80% of this carbon is stored belowground in the form of soil organic matter and permafrost. So when the forest burns, the carbon released from the trees is just the tip of the iceberg. Eighty percent or more of carbon emissions from boreal fires in North America and in central Siberia come from belowground combustion of soil organic matter.

Boreal forests have been reliable safekeepers of this belowground carbon historically by providing an insulating soil organic layer that protects permafrost. But increasingly severe fires are changing that picture.

What happens to permafrost when the boreal burns?

Wildfires threaten this belowground carbon in boreal forests in multiple ways, both during and long after the fire itself.

As a fire burns, it combusts the carbon stored in trees and plants, releasing it into the atmosphere along with smoke and harmful pollutants. Intense fires also burn through duff and soil layers that carpet the forest floor.

Burning these insulating layers exposes the permafrost below to warmer temperatures for years after a fire. A recent synthesis study led by Postdoctoral Researcher Dr. Anna Talucci of Woodwell Climate found that in burned sites across the boreal and tundra regions, the depth of seasonally thawed ground increased for two decades after a fire.

That means that long after a fire is extinguished, permafrost is still thawing and releasing carbon in the form of carbon dioxide and methane. Where this ground is rich in ice, it can sink and collapse after a fire, causing ponding, erosion, and creating bogs and wetlands that release methane.

All of this carbon released to the atmosphere contributes to further warming, which in turn contributes to drying forests, hotter temperatures, and more lightning ignitions in the boreal forests. That’s because warming has boosted both lightning ignition efficiency, or the likelihood that lightning starts a fire, and the number of lightning strikes in the region.

Average yearly burned area across Alaska and Canada has roughly doubled since the 1960s. Emissions from Canada’s 2023 fire season exceeded total fossil fuel emissions from every other nation except the U.S., China, and India for that year. And the frequency of extreme wildfires across the circumpolar boreal region increased seven-fold from 2003 to 2023.

These trends, amplified by the permafrost-fire feedback, worsen both Arctic impacts and global emissions and could hamper our ability to meet agreed-on climate goals.

Gaps in boreal fire research

Wildfires in boreal forests are already weakening the region’s carbon storage capacity, signalling a crucial shift in the global climate system. Addressing critical gaps in our understanding of the fire-permafrost feedback will help prepare for such shifts and their local and global implications.

Research teams including Permafrost Pathways and collaborators are refining tools to predict what increasing fires mean for regional and global carbon emissions and climate targets. Such insights are needed to inform the Intergovernmental Panel on Climate Change’s (IPCC) inventory of global emissions, which does not yet include fire emissions or fire-caused permafrost thaw emissions. Efforts to better model and predict the complex interactions between permafrost and fire are also critical to informing adaptation and management responses.

The region’s vastness, as well as geopolitical conditions, presents challenges to collecting field data. Here, modeling can help scale the insights from what field data is available. And developing more accurate fire maps in Alaska and Siberia, where less burned area satellite data exists, could equip researchers and communities with better near-real-time information. Long-term monitoring efforts that study pre- and post-fire conditions, such as those led by Łı́ı́dlı̨ı̨ Kų́ę́ First Nation at the Scotty Creek Research Station, are providing critical insights about fire’s acute and long-term effects on permafrost.

What we can do: solutions that support resilience

The impacts from widespread severe northern wildfires transcend boundaries, affecting health and ways of life for communities living in the Arctic and around the globe.

But there are solutions at hand. Cultural burning, an important practice for many Arctic Indigenous communities, can help boreal forests build resilience by removing fuels with low-intensity seasonal fire. And collaborative management approaches that suppress fires in permafrost regions have been shown to be a cost-effective climate mitigation tool that has co-benefits for human health and the global climate.

But the most important solution to help keep the global wildfire-permafrost feedback loop in check is to reduce greenhouse gas emissions. Lowering overall emissions will slow rising temperatures in the north and give communities, boreal forests, and other ecosystems a better chance to recover and to adapt.

In the Arctic, permafrost plays a crucial role in building infrastructure. However, as the region warms and permafrost thaws, infrastructure is threatened as the ground shifts beneath the built environment. Unfortunately, the full extent of the risks associated with this process is not yet realized, but researchers are working to address this knowledge gap.

Woodwell Climate Associate Scientist, Dr. Anna Liljedahl, along with UConn Department of Natural Resources and the Environment researchers Elias Manos and Assistant Professor Dr. Chandi Witharana developed a method that uses high-resolution satellite imagery and deep machine learning to map Alaskan infrastructure and more accurately project economic risks associated with permafrost thaw. Their findings published in Nature Communications Earth and Environment estimated that the costs of permafrost damage to infrastructure will double under low and medium emissions scenarios by 2050.

“Damages to infrastructure caused by permafrost thaw is on par with the average yearly cost of all natural disasters in the country, yet permafrost thaw is not recognized by the federal government as a natural hazard making it harder for people in Alaska to obtain disaster relief funding,” says Liljedahl.

This study is the latest from Witharana’s research group, which examines the ways satellites can help monitor changes in the Arctic landscape over time. According to Manos, in order to understand the hazards of a changing climate, we need a clear understanding of what’s at risk—in this case, vital structures like buildings and roads.

Permafrost serves as a structural foundation; piles are secured through it and buildings are often designed specifically to help the thermal integrity of this anchor layer. But the structural integrity of the layer, and consequently the structures above, is compromised as the permafrost thaws.

“When the temperature of permafrost starts to increase, piles start to shift out of place, and that’s what we call bearing capacity loss, or decrease in bearing capacity. That was the main hazard that we looked at which impacts buildings,” says Manos. “Then there’s also transportation infrastructure that’s primarily impacted by ground subsidence. When ice-rich permafrost thaws, the ground will cave in and that was the hazard we used to assess the disaster risk for roads.”

Previous studies have made risk estimates based on data from OpenStreetMap (OSM), which is one of the most widely used geospatial data sets available, says Manos. OSM is available for every nation across the globe, and information is updated by volunteers who manually input local data, like buildings, trails, roads, or other kinds of infrastructure, from high-resolution imagery on a global scale. For some regions, like Europe and parts of the United States, the data is accurate, says Manos, but that is not true for all locations. Unfortunately for the Arctic, OSM data is lacking.

“There are several previous risk studies that relied on this incomplete infrastructure data. It all goes back to the fact that infrastructure across the Arctic is not completely mapped, and that’s problematic if you want to understand disasters because you must have the full picture to understand the scale of what is or could potentially be exposed,” says Manos.

To fill in that picture, Witharana’s group developed a method to accurately map infrastructure and permafrost thaw risk called High-resolution Arctic Built Infrastructure and Terrain Analysis Tool (HABITAT). The model uses machine learning and AI to extract road and building information from high-resolution satellite images from the years 2018-2023. They compared the HABITAT data with OSM data to evaluate the new model’s quality and to look for potential misclassifications. Then they added the new information to OSM, nearly doubling the amount of information available for Alaska.

“The sheer amount of infrastructure and buildings that were missing from Open Street Map was, really shocking to me, 47% missing,” says Manos. “Though OpenStreetMap is a powerful volunteer-based resource, it has limitations and that is not a surprise.”

Witharana adds that by combining OSM data with the thousands of sub-meter resolution satellite images provided by the National Science Foundation, along with access to NSF supercomputing infrastructure, it was possible for the researchers to enhance the completeness of these datasets.

“We can see that impact and do better assessments of economic disturbances and risk so we can prepare for whatever policy actions or downstream efforts that are needed,” says Witharana “That’s a major outcome. Overall, the integration of AI and big data sets within our application has helped make useful, actionable products that researchers and communities can use right now.”

Witharana, Liljedahl, and Manos have plans to expand this analysis to account for the entire Arctic region to assess economic losses using a comprehensive infrastructure map.

“Alaska is decades behind the rest of the country in terms of geospatial data readiness. Maps are key for assessments and planning and I think the research community can help with some of that,” says Liljedahl.

Ecological warning lights have blinked on across the Arctic over the last 40 years, according to new research, and many of the fastest-changing areas are clustered in Siberia, the Canadian Northwest Territories, and Alaska. The analysis of the rapidly warming Arctic-boreal region, published in Geophysical Research Letters this week, provides a zoomed-in picture of ecosystems experiencing some of the fastest and most extreme climate changes on Earth.

Many of the most climate-stressed areas featured permafrost, or ground that stays frozen year-round, and experienced both severe warming and drying in recent decades.

To identify these “hotspots,” a team of researchers from Woodwell Climate Research Center, the University of Oslo, the University of Montana, the Environmental Systems Research Institute (Esri), and the University of Lleida used more than 30 years of geospatial data and long-term temperature records to assess indicators of ecosystem vulnerability in three categories: temperature, moisture, and vegetation.

Building on assessments like the NOAA Arctic Report Card, the research team went beyond evaluating isolated metrics of change and looked at multiple variables at once to create a more complete, integrated picture of climate and ecosystem changes in the region.

“Climate warming has put a great deal of stress on ecosystems in the high latitudes, but the stress looks very different from place to place and we wanted to quantify those differences,” said Dr. Jennifer Watts, Arctic program director at Woodwell Climate and lead author of the study. “Detecting hotspots at the local and regional level helps us not only to build a more precise picture of how Arctic warming is affecting ecosystems, but to identify places where we really need to focus future monitoring efforts and management resources.”

The team used spatial statistics to detect “neighborhoods,” or regions of particularly high levels of change during the past decade.

“This study is exactly why we have developed these kinds of spatial statistic tools in our technology. We are so proud to be working closely with Woodwell Climate on identifying and publishing these kinds of vulnerability hotspots that require effective and immediate climate adaptation action and long-term policy,” said Dr. Dawn Wright, chief scientist at Esri. “This is essentially what we mean by the ‘Science of Where.’”

The findings paint a complex and concerning picture.

The most substantial land warming between 1997-2020 occurred in the far eastern Siberian tundra and throughout central Siberia. Approximately 99% of the Eurasian tundra region experienced significant warming, compared to 72% of Eurasian boreal forests. While some hotspots in Siberia and the Northwest Territories of Canada grew drier, the researchers detected increased surface water and flooding in parts of North America, including Alaska’s Yukon-Kuskokwim Delta and central Canada. These increases in water on the landscape over time are likely a sign of thawing permafrost.

Among the 20 most vulnerable places the researchers identified, all contained permafrost.

“The Arctic and boreal regions are made up of diverse ecosystems, and this study reveals some of the complex ways they are responding to climate warming,” said Dr. Sue Natali, lead of the Permafrost Pathways project at Woodwell Climate and co-author of the study. “However, permafrost was a common denominator—the most climate-stressed regions all contained permafrost, which is vulnerable to thaw as temperatures rise. That’s a really concerning signal.”

For land managers and other decisionmakers, local and regional hotspot mapping like this can serve as a more useful monitoring tool than region-wide averages. Take, for instance, the example of Covid-19 tracking data: maps of county-by-county wastewater data tend to be more helpful tools to guide decision making than national averages, since rates of disease prevalence and transmission can vary widely among communities at a given moment in time. So, too, with climate trends: local data and trend detection can support management and adaptation approaches that account for unique and shifting conditions on the ground.

The significant changes the team detected in the Siberian boreal forest region should serve as a wakeup call, said Watts. “These forested regions, which have been helping take up and store carbon dioxide, are now showing major climate stresses and increasing risk of fire. We need to work as a global community to protect these important and vulnerable boreal ecosystems, while also reining in fossil fuel emissions.”

Explore these 15 maps by award-winning Woodwell Climate cartographers Greg Fiske and Christina Shintani. Created in 2024, each tells a story about the immense beauty of the high north, the dramatic changes unfolding as the Arctic continues to warm three to four times faster than the rest of the world, and the equitable solutions being developed to address climate impacts in the region