Wildfires in Arctic Alaska are now exceeding anything recorded in the region over the past 3,000 years, according to a new reconstruction that incorporates modern satellite data.
This increase suggests the Arctic tundra is no longer shielded by the cold, waterlogged ground that once made fires uncommon. Instead, it signals the emergence of a warmer, more fire-prone period, fuelled by drying soils and expanding shrubs.
Alaska wildfire history
Peat layers - deep soils formed from partially decomposed vegetation - have preserved minute charcoal particles throughout northern Alaska. A new study demonstrates how these traces reveal changes in wildfire activity.
Angelica Feurdean, a senior researcher at Goethe University in Germany, identified the sharp rise after 1950 by linking peat layers with satellite observations.
University of Alaska Fairbanks (UAF) field teams extracted nine cores, each roughly 51 cm deep, beside Alaska’s Dalton Highway. Once this long-term record had been established, researchers examined changes in soil moisture and vegetation cover for further evidence.
Across the first 2,000 years of the record, fires remained infrequent on tundra north of the Brooks Range in northern Alaska.
Charcoal fragments within the oldest layers indicated lengthy intervals between fires, including during a period of modest soil drying between A.D. 1000 and 1200.
Following that brief increase, the charcoal signal weakened once more and remained low for around 700 years, reflecting a prolonged absence of fire.
“The interlinked changes across millennia mean recent fires are indicators of a system undergoing rapid transformation,” said Feurdean.
Why soils dried out
Rising temperatures reduce the amount of water the ground can retain, making ignition more likely. As permafrost - ground that remains frozen for at least two years - thaws, water drains further down and the upper soil becomes drier.
By the middle of the century, peat surfaces at several sites had reached extreme levels of dryness, followed shortly afterwards by greater fire activity.
When peat surfaces lose moisture, lightning strikes or stray embers can spread flames across land that previously resisted burning.
Shrubs drive Alaska wildfires
The expansion of shrubs has changed areas of tundra from open grassland into denser, woodier vegetation that ignites more easily.
In the study region, woody encroachment favoured Ericaceous shrubs: low-growing woody plants from the heather family that burn readily when dry.
A greater number of shrubs created more fuel above ground, and the peat cores showed that their spread coincided with the increase in fires.
This added fuel is particularly important in hot, dry summers, when flames can travel through brush that was once too damp to burn.
Satellites confirm the surge
Recent satellite observations support the charcoal evidence, showing repeated fires across Alaska’s North Slope since the late 1960s.
The researchers used the Alaska Interagency Coordination Center dataset to compare mapped burn perimeters with nearby core locations.
The satellite record highlighted several distinct periods, including clusters of fires during the 1990s and again from the 2000s into the 2010s.
However, satellites only cover the most recent decades, making the peat record essential as a baseline for assessing just how unusual current conditions are.
When fires burn hotter
Fire size alone could not account for the charcoal patterns, as some of the largest recent fires produced unexpectedly faint charcoal signals.
Intense heat can burn vegetation almost entirely, converting a larger share of plant material into ash and leaving less charcoal to be deposited later. This pattern could point to a changing fire regime in which fires are burning far hotter.
More intense fires also complicate the long-term record because a severe blaze may destroy evidence of its own charcoal signature.
Carbon stored underground
Arctic soils can store carbon for centuries, meaning fires in this region can have global consequences. Certain Arctic wetlands accumulate fuel over hundreds of years, while these peatlands - wetlands made up of partially decomposed plants - may smoulder beneath the surface.
In 2007, Alaska’s Anaktuvuk River fire burned about 1,038 km² and released approximately 2.1 billion kg of carbon.
More frequent tundra fires can transform carbon stored in soil into air pollution and heat-trapping gases, extending the consequences far beyond Alaska.
Risks beyond the tundra
Smoke from fires in the far north can travel hundreds of miles, leaving people downwind exposed to the particles it carries.
When a fire reaches thick organic soil, it gains additional fuel, allowing a single tundra blaze to smoulder and produce smoke for days.
The remoteness of the terrain restricts firefighting choices, so crews often focus on safeguarding roads, pipelines and camps instead of pursuing every fire.
After a fire, scorched land takes in more sunlight, potentially accelerating thaw and leaving the same area drier during future summers.
Future of Alaska wildfires
Long-term records allow land managers to move away from viewing Arctic fires as rare events and towards preparing for regular fire seasons.
By combining peat histories with contemporary maps, UAF scientists can identify locations where dry soil and shrub growth make the next ignition more likely.
Improved monitoring of soil moisture and shrub cover can inform staffing decisions and help protect important sites during lightning storms.
Even with more effective planning, reducing greenhouse gas emissions remains the only way to slow the drying that is driving this new era of fire.
Taken together, peat layers and satellite maps show that tundra fires are now sustained by dry ground and woody fuel that were once limited.
Future research will examine whether hotter fires continue to weaken charcoal signals, potentially obscuring the real extent of fires to come.
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