A Zombie-Fire Outbreak may be Growing in the North
Freeman writes:
A zombie-fire outbreak may be growing in the north:
Each winter, as snow blankets Alaska and northern Canada, the wildfires of the summer extinguish, and calm prevails-at least on the surface. Beneath all that white serenity, some of those fires actually continue smoldering underground, chewing through carbon-rich peat, biding their time. When spring arrives and the chilly landscape defrosts, these "overwintering" fires pop up from below-that's why scientists call them zombie fires.
Now, a new analysis in the journal Nature quantifies their extent for the first time, and shows what conditions are most likely to make the fires reanimate. Using satellite data and reports from the ground, researchers developed an algorithm that could detect where over a decade's worth of fires-dozens in total-burned in Alaska and Canada's Northwest Territories, snowed over, and ignited again in the spring. Basically, they correlated burn scars with nearby areas where a new fire ignited later on.
[...] Northern soils are loaded with peat, dead vegetation that's essentially concentrated carbon. When a wildfire burns across an Arctic landscape, it also burns vertically through this soil. Long after the surface fire has exhausted the plant fuel, the peat fire continues to smolder under the dirt, moving deeper down and also marching laterally. In their analysis, Scholten and her colleagues found this is most likely to happen following hotter summers, because that makes vegetation drier, thus igniting more catastrophically. "The more severe it burns, the deeper it can burn into that soil," says VU Amsterdam Earth systems scientist Sander Veraverbeke, co-author on the new paper. "And the deeper it burns, the higher the chances that that fire will hibernate." Even when autumn rain falls or the surface freezes in the winter, water isn't able to penetrate the soil enough to entirely extinguish it.
Then spring arrives and the ice retreats. These hot spots can flare up, seeking more vegetation to burn at the edges of the original burn scar. "Basically, right after the snow melts, we already have dry fuel available," says Scholten.
Journal Reference:
Rebecca C. Scholten, Randi Jandt, Eric A. Miller, et al. Overwintering fires in boreal forests, Nature (DOI: 10.1038/s41586-021-03437-y)
Read more of this story at SoylentNews.