Driven by climate warming, summer convection, thunderstorms and lightning will occur more frequently and intensely in the future, potentially altering Arctic landscapes. “More lightning in the Arctic means more fire,” said Sander Veraverbeke, associate professor in Climate and Ecosystems Change at VU Amsterdam and co-author of the study. Results of the study are published in Nature Climate Change.
Lightning to more than double
The international team used NASA satellite observations of summer lightning in the Arctic together with meteorological proxies that closely relate to lightning such as convection and rainfall. “Our statistical model explained 66 % of the spatial and temporal variability in contemporary lightning”, explained Yang Chen, a researcher at UC Irvine and lead author of the paper. “When we extrapolate our model to the future, we find that there will be more than a doubling of the amount lightning in the Arctic by the end of century,” Chen further said.
Fire-induced permafrost thaw causing carbon emissions
The team also observed that the lightning increases will be larger for the tundra than for the more southern boreal forest. In the boreal forest, they estimate about an 85% increase in summer lightning, while in the tundra the expected rate of change is nearly twice as high. “That is a very interesting outcome of the study, as it implies that carbon stored in peat and permafrost soils will become increasingly vulnerable to fire,” according to Veraverbeke. Veraverbeke further explained that fires may accelerate permafrost thaw for many years to decades after the fires, which could lead to additional emissions of greenhouse gases. “These carbon emissions from fire-induced permafrost thaw have really not well been quantified,” said Veraverbeke, and this is one of the major research questions of Veraverbeke’s recently granted ERC consolidator project called FireIce.
“More fire in the Arctic will trigger a cascade of ecological changes,” James Randerson, Professor of Earth System Science and senior author of the publication, continued. “Fires remove organic material from the surface, making it easier for trees to grow on the remaining mineral soils.” Driven by climate warming, post-fire soils could thus provide the perfect conditions for shrubs and trees to move farther North in what is now tundra. “This sounds contradictory, but as such tundra fires may stimulate the growth of shrubs and trees in the Arctic”, Randerson explained. This too would have repercussions for climate as snow cover remains longer in spring in the tundra compared to vegetated areas. “Snow reflects solar energy and an earlier snow melt in vegetated areas would thus result in regional surface heating. More shrubs and trees in the Arctic will thus have a warming effect,” according to Randerson. “Our study indicates that lightning is a forceful Earth system process in the Arctic, and more of it is coming,” Randerson concluded.
The study stems from a collaboration between the University of California, Irvine, Vrije Universiteit Amsterdam, University of California, Berkeley and Lawrence Berkeley National Laboratory.