Lightning strikes have become more common in the Arctic over the last decade, and they’re expected to become ever more frequent over the next century. Two new studies present evidence that the phenomenon is linked to climate change, and that the wildfires sparked by Arctic lightning will accelerate climate change even more.
A study published last month in the journal Geophysical Research Letters shows Arctic lightning strikes have become 300 percent more common in the last 11 years. The Arctic’s climate is warming twice as fast as the rest of the world, and its warmer air provides the right conditions for lightning to strike, Maria Temming reports for Science News. A study published this week in the journal Nature Climate Change combines satellite records of Arctic lightning with global climate models to predict that lightning strikes could become twice as common by the end of the century.
Right now, lightning strikes are the only natural cause of wildfires in the Arctic, says University of California Irvine climate scientist Yang Chen, first author of the Nature Climate Change study, to Philip Kiefer at Popular Science. When permafrost burns, it releases immense amounts of greenhouse gases that contribute to the warming climate that causes more lightning strikes.
All together, that creates a climate change-accelerating cycle.
“The Arctic is a rapidly changing place, and this is an aspect of the transformation that I'm not sure has gotten a whole lot of attention, but it's actually really consequential,” says University of California, Los Angeles, climate scientist Daniel Swain, who was not involved in the new studies, to Matt Simon at Wired.
When warm, humid air rises from the ground and hits the cold air in the upper atmosphere, the moisture suddenly condenses. At the same time, the cold air sinks toward the ground. When the two air systems mix into a deep convective cloud, the cloud can create lightning.
When lightning hits the ground, it creates low-frequency radiation that acts “like a very long antenna in the sky,” says Robert Holzworth, the director of the World Wide Lightning Location Network, to Eos’ Katherine Kornei. Hozworth led research the network to calculate the frequency of lightning strikes in the Arctic in the last decade. In 2010, Arctic lightning accounted for about 0.2 percent of lightning strikes on Earth; by 2020, it accounted for just over 0.6 percent.
The results should be taken with a grain of salt because the decade of data is a relatively small stretch of time for climate science, and because “we need more stations in the high north to really accurately monitor the lightning there,” says VU University Amsterdam earth systems scientist Sander Veraverbeke to Science News.
The dataset shows in 2020, the Arctic saw an unusually high number of lightning strikes and wildfires. Lightning strikes on in the tundra can cause so-called “zombie fires” that start during one summer and smolder underground when they’re covered by snow, then reemerge the next the summer. The fires burn away the top layer of moss and grass, and burn into the peat, which is a dense layer of ancient plant material.
“That blanket keeps the permafrost cold. And as the fire burns into that blanket of duff, the underlying ground is exposed and warmed,” says University of Alaska Fairbanks fire ecologist Alison York, co-author of the Nature Climate Change study, to Popular Science.
At the root of the tundra is permafrost, a layer of ancient organic material like plants that froze before it could decay. If it starts to melt, it will release immense quantities of greenhouse gases, like methane, that could accelerate further lightning strikes, wildfires, and permafrost melting.
When permafrost melts, it is no longer able to reflect the sunlight or the heat that comes with it. It also gives large vegetation, like shrubs and trees, a chance to move into the area. Vegetation makes the landscape darker in color, so it absorbs more heat, and further accelerates the cycle of permafrost melting and greenhouse gas emissions.
York tells Popular Science that trees haven’t migrated into the tundra on a broad scale yet, but on a smaller scale, a giant tundra fire in 2007 led to the introduction of willow trees and other foliage that can be seen today. Local regions that saw an increase of shrubs also saw an increase in wildfires.
“Shrubs like to grow where there has been disturbances, such as fire and permafrost thaw. So more fire in the tundra could mean more shrubs,” says University of Edinburgh ecologist Isla Myers-Smith to Wired. “Shrubs grow more when summers are warmer and when water isn’t limited, so we expect an expansion of shrubs with future warming in the tundra.”