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The intense summer heat that sparks wildfires in the forests may be the mysterious cause of a strange, rare phenomenon: zombie fires. These “undead” flames smolder deep underground in the carbon-rich peat soil, and then coalesce months later.
In a new study published in the journal Nature, an international team of researchers has revealed how they used complex computer algorithms to detect zombie fires rising from their peat-filled graves. in satellite images.
The zombie fires, also known as overwinter fires or trapped fires, are different from the fires that have ravaged California and Australia in recent years.
Deep in the carbon-rich soil and insulated by thick snow, zombie fires can smolder for months, long after firefighters have extinguished the flames on the surface. As the snow melts and the soil begins to dry, flames can flare back up to the surface and cause larger blazes. This poses a problem not only for people and property, but also for the climate.
Rebecca Scholten, an Earth system scientist at Vrije Universiteit Amsterdam in the Netherlands and one of the study’s authors, told Pop Mech, the top three meters of land in the Canadian boreal forests are covered. is estimated to contain twice the amount of carbon in the Earth’s atmosphere. Scientists have long considered boreal forests to be a carbon sink, meaning they absorb carbon dioxide from the atmosphere and thus mitigate some of the most devastating effects of climate change.
But in recent years, the scale has increased.
In terms of area burned and carbon dioxide emissions, 2020 is the Arctic’s worst fire year since scientists began keeping records in 2003. According to the Gas Monitoring Service In the Copernicus atmosphere, the Arctic fires that burned between January and August 2020 released a staggering 244 million tons of carbon into the atmosphere. Zombie fires burning through peat soil are particularly harmful and can release up to 100 times as much carbon into the air as a typical forest fire.
Jessica McCarty, geographer and satellite data: “These fires consume carbon in ancient soils, potentially thawing nearby permafrost and reducing boreal forests’ ability to become global carbon sinks., experts at the University of Miami, told Pop Mech.
How to deal with these fires?
Of course, the first step in fighting zombie fires is finding them. So Scholten and her colleagues created an algorithm to help detect fires in satellite imagery and identify patterns that could help fire crews better focus their resources.
First, the scientists trained the algorithm using field and remote sensing data collected between 2005 and 2017 from more than 50 fires in the deep forests of Alaska and the Northwest Territories of Canada. . As zombie fires slowly crept beneath the soil, the scientists taught the algorithm to focus on fires that flared around the edges of the previous year’s burn.
The scientists also ruled out fires that are too close to population centers because they could be caused by humans inadvertently, plus fires that broke out after June, when lightning strikes in the area (a source of ignition) main) increases.
Using an algorithm, the team discovered 20 previously unreported zombie fires between 2002 and 2018. During the study period, these fires were very rare, accounting for only 0.8 percent of the total. number of areas burned during that time. But over the years, the burned area increases. For example, in 2008, a zombie fire that burned nearly 34,000 acres across Alaska accounted for about 38% of the total burned area that year.
After analyzing the results, Scholten and her colleagues found several factors that could set the stage for these fires to persist through the Arctic’s notoriously harsh winters.
Scientists have found that the majority of zombie fires occur in the spring after years with warmer summers, marked by severe wildfires. The zombie fires appeared in the spring after the six hottest years of the study period. In Alaska, the spring after 2009 and 2015 – years of high fire incidence – saw a number of zombie fires arise. No zombie fires broke out in the spring after the seven coolest summers.
The size and intensity of the fires that broke out the previous summer also played a role in the outbreaks the following spring. Study co-author Sander Veraverbeke, also an Earth system scientist at Vrije Universiteit Amsterdam, told Popular Mechanics: “As these fires become more intense, they will burn deeper into the layer [đất] Organic. If fires can take root deeper in the soil, they have a better chance of surviving the winter.
Scholten says: “The northern forest regions are also the regions where climate change is happening the fastest. We see temperatures warming twice as fast as the global average there.”
While zombie fires are still a relatively rare phenomenon, these numbers are likely to increase as temperatures soar and fires become more intense.
Ultimately, this research could help fire managers better allocate resources in deep forests and prevent small outbreaks from spiraling out of control. Because scientists find many of these fires start around the previous year’s burn, for example, firefighters can focus their surveillance efforts on that area in the year following the major fire.
Knowing more about this is helpful for everyone, even if it seems a bit intimidating.
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