There is strong evidence that last summer鈥檚 unprecedented Arctic blazes appear to have smouldered through winter as聽鈥渮ombie fires鈥� and reignited this month.
Intense blazes across the frozen north last year led to record carbon emissions that were on a par with those from Belgium, exacerbating the global warming that made the conditions for the fires possible in the first place.
Now as temperatures rise in the region and snow recedes, satellite analysis of last year鈥檚 burn sites and the fires erupting this month suggest many in Siberia may be zombie fires.
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鈥淲e know they are real and quite rare. That鈥檚 why seeing so many potential spots in Siberia is interesting. The satellite images are astonishing, particularly the snowmelt immediately followed by the fires appearing,鈥� says Thomas Smith at the London School of Economics.
In an analysis for New 杏吧原创 based on imagery from the European Space Agency鈥檚 Sentinel-2 satellites, Smith identified 2019 burn scars and 2020 hotspots and found overlap of fires from last July and fires that appeared immediately after snowmelt this year. This includes known peatlands in tundra north of the boreal forest, where peat below ground could smoulder through winter. 鈥淚 think there is some strong evidence for zombie fires,鈥� he says.
The tentative signs of this come as said fire managers in Alaska have found such fires occurring more frequently in the past two decades.聽Significantly, given 2019鈥檚 record-breaking blazes, they found zombie fires are more likely to occur the year after a large fire year. The new blazes usually re-emerge within 50 days of snow melting, they added.
If more fires are surviving winter, that is bad news for climate change, says Smith. 鈥淭he implication is greater net carbon emissions, given that overwintering fires, by their nature, are smouldering soil and peat fires, burning through long-term carbon stores.鈥�
Mark Parrington at the European Centre for Medium-Range Weather Forecasts in the UK echoes the risk of a knock-on effect. 鈥淚f these are zombie fires and they are quite widespread in areas that were burning last summer, then, under the right environmental conditions, there may be a cumulative effect of the previous fire season feeding into this coming season and leading to large-scale and long-term fires across the region again,鈥� he says.
Without reports from the ground, Smith says we can鈥檛 know for certain if they are zombie fires or new ones lit by people as snow melted. But he says: 鈥淭he fires seem so widespread and so sudden that I find it hard to believe that humans could have been everywhere at once in such a sparsely populated place.鈥� Another reason to think they are zombie fires is that the ignition appears in spots, rather than the lines or perimeters that are more likely if people are starting the blazes, he adds.
Nonetheless, Anton Beneslavskiy at Greenpeace in Russia thinks intentional burning by people is more likely to be the cause in Siberia, noting past surveys have shown most fires start near roads and logging sites. While he says zombie fires are possible, he adds: 鈥淭here is no clear evidence they were the reason for the fires of the last week.鈥�
One way to mitigate against zombie fires is more monitoring on the ground and extinguishing them in winter, says Jessica McCarty at Miami University in Florida. 鈥淢ost zombie fires in Alaska have been caught because hunters or snowmobilers report the locations to the Alaska Forest Service. Without that in-situ info, we would never find them with satellite data, as they are often still partially covered in snow.鈥�
