For the second straight year, an unusually large number of intense fires have ignited in the Arctic Circle, the polar region atop Earth.
It's now been anomalously warm in Siberia for nearly six months, and temperatures likely eclipsed triple digits in a Siberian town last weekend — setting a heat record for the Arctic Circle. This streak of warm and hot conditions has set the stage for blazes to torch the dried-out region. Last year, unprecedented fires burned in the Arctic Circle, and new data from Copernicus, the European Union's earth observation agency, show the number and intensity of fires is similar in 2020.
The robust blazes are problematic because burned forests and vegetation release copious amounts of heat-trapping greenhouse gases into the atmosphere (CO2, for example, is a primary ingredient in smoke), particularly when thick mats of decomposed, carbon-rich vegetation, called peat, ignite. Of the 18 years researchers have used satellites to closely monitor Arctic fires, 2019 and 2020 have emitted more CO2 into the atmosphere than the previous 16 years combined, said Thomas Smith, an assistant professor in environmental geography at the London School of Economics.
"The two years together is quite alarming," said Smith. "I don't use that word lightly."
Over just six weeks last year, Arctic Circle fires released more carbon dioxide into the atmosphere than Sweden does in an entire year, according to the World Meteorological Organization.
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As the Earth's climate continues to relentlessly warm, the recent fires could be a harbinger of substantially more burning in the Arctic Circle. Yet, the 18-year wildfire satellite record (started via NASA satellites in 2002) is still too short to conclude with certainty that these recent fire years are evidence that the fire regime in the Arctic Circle has dramatically changed. Still, there's growing evidence that change is afoot in forests and tundra atop the globe.
"With confidence, we can say that this does appear to be an increasing trend of fire," said Jessica McCarty, an Arctic fire researcher and assistant professor in the Department of Geography at Miami University. "There’s some shift occurring."
She emphasized that recent fire activity in the region "is an interesting finding," but it will take years of further observation to confirm if it's part of a big, sustained trend. Fire seasons are naturally cyclical, meaning there can be bigger fire years followed by less intense periods as the landscape recovers and vegetation regrows. Additionally, Siberia has been smothered by atypically warm temperatures for nearly six straight months. Some years will inevitably be cooler, which may mean less favorable conditions for flames.
There's a diversity of ecosystems burning in the Arctic right now, according to an analysis by Smith, including forested areas, shrublands, and tundra. Importantly, the ground in some of these burning areas is peat (though it's hard to precisely estimate how much), which means old, thick deposits of carbon are burning and releasing the potent greenhouse gases carbon dioxide and methane into the air.
This adds more heat-trapping gas to an atmosphere that's already loaded with the highest levels of carbon dioxide in at least 800,000 years, but more likely millions of years.
"You're losing a carbon store," said Smith. "It is thousands of years old. If we're thinking about climate change, it's going to take thousands of years for that carbon to accumulate [in the soil and vegetation] again."
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An important takeaway from the last two extreme years of Arctic blazes isn't that there's bound to be such intense fire seasons each summer now, but that ever-warming environmental conditions allow for such atypical burning to be possible, or increasingly possible. "We don't expect these fires all the time," said McCarty. "But we know the landscape can burn."
During the spring, some of 2020's Arctic fires may have been zombie fires, or holdover fires, which survive underground during the winter and then reemerge the following year. But overall, some 85 to 95 percent of fires are ignited by humans, either intentionally or accidentally, explained McCarty. Yet lightning strikes often start the biggest Arctic fires, she said, and as the region incessantly warms and the air becomes more humid in the summer, this polar region could see more lightning.
"In the future, we expect more lightning strikes in the Arctic in a warmer climate — thus more potential for Arctic fires," said McCarty.
There will be more burning in the Arctic Circle this summer, as a stagnant, warm weather pattern continues to heat the region. And as with any heat wave today, particularly in the fast-changing Arctic, hot weather patterns are amplified by climate change. This means heat events today are warmer than they would have been without human-caused global warming.
Under these hot and dry conditions, Siberia is an expansive land that's primed to burn. "You’ve got so much dried-out material," said Smith. "It can burn, and burn, and burn."
