Arctic warming will increase permafrost megafires

In 2019 and 2020, the Siberian Arctic experienced an unusual number of devastating fires, raising concerns in the scientific community, as the Arctic has vast areas of permafrost – a permanently frozen layer of subsoil which accumulates large amounts of carbon. The fires significantly damage the permafrost and contribute to the release of carbon emissions in the atmosphere. But was this increase in fires in 2019-2020 an exceptional case or a trend that will become worse as the Arctic warms?

By analyzing satellite observations between 1982 and 2020, a team of researchers led by the Spanish Council for Scientific Research (CSIC) has found that, although these fires were indeed exceptional, global warming will most likely drive increasingly more megafires over the following decades, releasing massive amounts of carbon.

“In 2020 alone, 423 fires were detected in the Siberian Arctic, which burned around three million hectares (an area almost as big as the whole Belgium) and caused the emission of 256 million tons of CO₂ equivalent [similar to the annual emissions of CO₂ in Spain]. With future warming, these megafires will be recurrent at the end of the century and will have different implications, both for the Arctic and for the global climate,” said study lead author Adrià Descals, a research scientist at CSIC.

“We detected fires above the 72^nd parallel north, more than 600 km north of the Arctic Circle, where fires are unusual and where winter ice was still visible at the time of burning. Many fires were detected with a few days of difference, so we hypothesize that increases in thunderstorms and lightning are the main cause of the fires, although further investigations would be required to demonstrate how much human activities may influence the fire season in this remote region.”

According to the scientists, the concatenation of several factors related to rising temperatures, such as drier weather conditions, longer summers, and more vegetation, is what generated the fire rate increase, and will likely increase the frequency of such events in the future.

“The fact that there is more and earlier vegetation reduces the availability of water in the soil, and plants suffer greater water stress,” said Aleixandre Verger, a researcher at CSIC. In turn, “extreme heat waves, such as in 2020 in the Siberian Arctic, increase vulnerability to drought, as they can desiccate plants and reduce peat moisture, and therefore increase the intensity of fires and carbon emissions.”

“Climate warming therefore has a double effect on fire risk: it increases the susceptibility of vegetation and peatlands to fire and, on the other hand, it increases the number of ignitions caused by thunderstorms,” added Descals.

“The areas burned in 2019 and 2020 could be exceptional events, but recent temperature trends and projected scenarios indicate that, by the end of the century, large fires such as those in 2019 and 2020 will be frequent if temperatures continue to increase at the current rate,” the scientists concluded.

The study is published in the journal Science.

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By Andrei Ionescu, Earth.com Staff Writer