Researchers believe they may have solved the mystery of “zombie fires” inside the Arctic Circle, which disappear underground in winter only to re-emerge and burst into flames again in spring.
These fires occur in peatlands in Siberia, Canada and Alaska. Researchers originally thought the fires started on the surface and continued smouldering underground. Now there is a different explanation.
When microbes break down peat, the process generates heat. Much as a haystack can spontaneously combust due to the action of microbes, which raise its temperature past the flashpoint, peat can get dangerously hot. But it does not catch fire until the air temperature rises in spring.
Research from the University of Cork, published in the Proceedings of The Royal Society, suggests that it is not so much the absolute air temperature that matters as how fast it rises. Rapid warming causes the process to accelerate until a tipping point is reached where it produces flames. This may explain why zombie fires, rare a century ago, have become more common as the climate changes.
The researchers say further work is needed to refine their computer model, for example with details of soil hydrology. Given that zombie fires could release billions of tonnes of stored carbon, they are likely to be a major concern.
