Lightning in the Arctic was formerly so vanishingly rare that people could go their whole lives without seeing a flash. But as the region warms up rapidly, it could become more common – with consequences that could extend beyond the Arctic.
One recent study projects that the prevalence of lighting in the Arctic could double by the end of the century. Another study suggests that the number of Arctic flashes has only tripled in the past decade – although some researchers question the result.
Increasing lightning is a worrying sign of today’s rapidly accelerating climate change, scientists say, but they are also worried about the future: more lightning could cause a waterfall of ecological shifts that could release large Arctic reserves of carbon into the atmosphere, heating can accelerate. further.
‘The previous numbers [of lightning flashes] was small, but it can have a huge climate impact, ”says Yang Chen, a researcher at the University of California, Irvine, and lead author of one of the new studies, published in Nature Climate change.
The lightning fires are increasing
In 2002, when researchers interviewed indigenous elders from a North Pole community in northwestern Canada, no one could remember seeing more than a few lightning storms during their lifetime. One elder remembers seeing a single storm in the 1930s, when she was just five years old.
Scientists at the time also did not really think about Arctic lightning: it was so rare that even researchers who had spent decades in the region may never have seen a flash.
“When I first came to Fairbanks, I would see a thunderstorm and I would be amazed,” said Uma Bhatt, a meteorologist at the University of Alaska, Fairbanks, who studied lightning in the North Pole and in the North Pole. state has lived for 22 years.
In 2014 and 2015, some of the largest fires ever recorded burned over large parts of Alaska and the Northwest Territories of Canada. Like more than 90 percent of all fires in the Arctic, it is caused by lightning.
As the Arctic grows and dries, plants become more flammable. But after 2014 and 2015, Sander Veravebeke, a climate scientist at the Vrije Universitat in Amsterdam and co-author of one of the recent articles, wondered if there was another piece of the story: did the lightning flashes that started fires also become more common?
“I looked at the lightning data for those years and saw, okay, it’s not coincidental,” says Veravebeke, “an increase in lightning almost immediately leads to an increase in fire. ‘
In a 2017 newspaper, he and colleagues found that the number of lightning fires in Alaska and the Northwest Territories has more than doubled since 1975, setting a record number in both places during the devastating 2014 and 2015 seasons.
Is there more lightning?
But did the lightning actually flash more frequently in the Arctic? This seems to be a difficult question to answer because there is no consistent, constantly measured Arctic report on the phenomenon.
A satellite launched in 1995 recorded polar lightning flashes, but it retired in 2000. Newer lightning-sensitive satellites see just as far north and south as the mid-latitude, not as far as the poles.
Ground-based networks, which use sensors that detect the light waves produced by lightning bolts, are now recording flashes that occur virtually anywhere in the world. Bhatt, which uses a regional network in Alaska, found a 17 percent increase in lightning activity between 1986 and 2015.
But records in the Arctic are short and span less than 20 years and are still not conclusive in documenting a solid trend, climate scientists say.
Recently, a team at the University of Washington dug into data from the World Wide Lightning Location Network, a rural network of sensors that has been in use since 2004. in 2010 to about 250,000 in 2020. Some of that can be attributed to an increase in the number of sensors, the researchers say, but estimates that lightning in the region has grown by a factor of three over the past decade.
However, another global lightning detection network run by the company Vaisala is not getting this dramatic increase. The Global Lightning Database 360 went live in 2012, so their record is shorter than the Washington team’s, but the network is more sensitive and records more and fainter flashes than the others.
But from 2012 to 2020, they did not record any significant increase in lightning activity, says Ryan Said, a research engineer at Vaisala. It does not necessarily mean there is not a trend, he says – only that it will take more years of observation to really figure out how the patterns change.
“It’s really just the beginning of the journey,” he says.
The Vaisala lightning network has detected unusual activities over the past few years. In the summers of 2019 and 2020, the GLD360 recorded more than 100 flashes north of 85 degrees – including a wave of ultra-rare lightning within 300 nautical miles of the North Pole.
More lightning is likely to come
Whether the shifts are already taking place or not, climate change means that lightning will almost certainly come to the Arctic, says Chen.
Lightning formation requires some very specific ingredients that were rare in the far north, but that climate change may be more common.
First, air at the surface must be warm and full of moisture, ready to move quickly. The air above should be cold enough that when the hot air shoots upwards, the moisture freezes into small ice particles. The whole system must be so turbulent that the air swirls and rolls, and swings so forcefully around the ice particles that it strikes electrons apart and is electrically charged. And then, finally, the giant discharge will take place, either within the cloud or between the cloud and the ground.
The Arctic’s cold, relatively stable atmosphere was not yet hospitable to thunderstorms. But air temperatures in the region have risen just one to two degrees Celsius over the past three decades, faster than anywhere else on the planet.
Chen and his colleagues, including Veravebeke, wanted to estimate how much lightning could cause the changing climatic conditions by the end of the century. They compared the lightning data of the satellite that recorded Arctic flashes in the 1990s with weather data from the same period to find out what atmospheric conditions best correspond to the rare lightning incidents in the region.
Climate models projected the specific lightning conditions and lightning – which is slightly different from the general probability of thunderstorms – would probably occur about one and a half times as often over the tundra in the future and almost double over the northern forests. This is a much larger relative change than the 50 percent increase projected for the continental US worldwide. According to some research, there may be a decrease total lightning by 2100, partly because the lightning-rich tropics can become so hot that ice crystals form less frequently.
It is not possible to estimate the satellite data used by Chen and his colleagues with the terrestrial networks used to detect the recent increase in activity, and therefore the two results cannot be directly compared or integrated. But both emphasize that “the North Pole is becoming more important,” says Veravebeke.
The lightning feedback loop
But the greatest resistance is not the lightning itself; this is what lightning can do. Wildfires around the world can release the carbon stored in forests and soils. The Australian wildfires in 2020, for example, released more than 800 million tonnes of carbon dioxide, almost one and a half times the country’s annual total.
Fires not only burn woody things on top of the ground. “Fire is three-dimensional,” explains Michelle Mack, an ecologist and Arctic expert at Northern Arizona University. It burns organic material in the soil under the flames – and the soil in the Arctic is much richer in carbon than in other parts of the world. It often contains dozens of accumulated carbon just in the top few inches. Arctic fires scrubbing the surface soil could release at least twice as much carbon as their California counterparts, Veravebeke said.
The research suggests that the area burned and the carbon emitted from the Arctic, by the end of the century, just because more lightning makes more fire, could increase by more than 150 percent compared to the average annual fire-related emissions of about 3.4 million tons of carbon.
But it can get worse. Fires are changing the ecosystem and facilitating the march to forests and shrubs northward by opening up new areas for growth. This in turn increases the chance of fires, because woody things catch fire more easily than tundra.
Forests are also warmer and therefore more flammable than tundra, because they are darker and therefore absorb more sunlight. If lightning-induced fires increase and accelerate the northward distribution of forests, Chen and his colleagues found, carbon emissions could increase by 570 percent compared to today, which could add about 23 million tons of CO2 a year to the atmosphere – about a fifth axis much 2020’s catastrophic in California.
The team outlined, but did not do the math about the frightening carbon concern: that lightning-induced fires could also expose the carbon-rich permafrost that underlies five million square kilometers of the Arctic, accelerating the rate at which it thaws and the huge stores of trapped carbon. In other words, that 570 percent increase in carbon emissions? “This is the lowest point of the estimates,” says Chen.