Climate warming may lead to more frequent lightning strikes in the Arctic

A bolt of lightning flashes across the sky during a storm in Canada's Yukon Territory. Photography: PRISMA BY DUKAS PRESSEAGENTUR GMBH/ALAMY STOCK PHOTO

Written by: ALEJANDRA BORUNDA

Once upon a time, lightning in the Arctic was so rare that people could see it in their lifetimes Less than a flash of lightning. But the region is warming rapidly, and lightning is becoming more common and may even affect places beyond the Arctic.

A recent study predicts that the frequency of lightning strikes in the Arctic could double by the end of the century. Another study shows that the number of Arctic lightning strikes has tripled in just the past decade, though some researchers are skeptical of the results.

Scientists say the increase in lightning is worrisome as climate change accelerates; they also worry about the future: More lightning could cause a cascade of ecological changes that would release huge amounts of carbon stored in the Arctic into the atmosphere , further accelerating climate warming.

"In the past, the number (of lightning) was very small, but the climate impact was very large," said Chen Yang, a researcher at the University of California, Irvine, and the lead author of one of the studies. The research was published in Nature Climate Change.

Lightning-triggered fires are on the rise

In 2002, researchers interviewed Aboriginal elders in Arctic communities in northwest Canada who could not recall seeing many fires in their lives. A thunderstorm. One elder recalled that she had only seen one storm in the 1930s, when she was only 5 years old.

At the time, scientists had not imagined lightning in the Arctic: the phenomenon was so rare that even researchers who had spent dozens of summers working in the Arctic had probably never seen lightning.

"The first time I came to Fairbanks, I was surprised to see thunderstorms," ??said Uma Bhatt, a meteorologist at the University of Alaska Fairbanks. She has lived in Alaska for 22 years and has studied lightning in the Arctic.

In 2014 and 2015, the largest fires on record ravaged large swaths of Alaska and Canada's Northwest Territories. Like more than 90% of fires in the Arctic, these fires are caused by lightning strikes.

As the Arctic becomes warmer and drier, plants are becoming more flammable. But after 2014 and 2015, Sander Veravebeke, a climate scientist at Vrije Universiteit Amsterdam and co-author of a recent paper, wondered about another factor: Could the lightning that causes fires also become more common?

"I checked the lightning data over the years and found, OK, this is not a coincidence," Veravebeke said. "Increases in lightning almost directly lead to increases in fires."

In 2017 In their paper, he and his colleagues found that the number of lightning-ignited fires has more than doubled in Alaska and the Northwest since 1975; during the catastrophic seasons of 2014 and 2015, the number of fires in both places exceeded recorded.

More lightning?

But is lightning really happening more frequently across the Arctic? This is a difficult question to answer because there are no sustained records of lightning in the Arctic range.

A satellite launched in 1995 recorded polar lightning, but it was decommissioned in 2000. The new lightning-sensing satellites can only observe conditions in the far south and north, as well as mid-latitudes, and cannot directly observe the poles.

Ground-based networks using sensors that detect the radio waves produced by lightning can now record lightning almost anywhere in the world. Using a regional network in Alaska, Bhatt found that lightning increased 17 percent from 1986 to 2015.

But records in the Arctic are scant, spanning less than 20 years, to prove a steady trend, climate scientists say.

Recently, a team of researchers at the University of Washington studied data from the Global Lightning Location Network; a network of land-based sensors that has been operating since 2004. They found that the number of lightning strikes recorded at 65 degrees north latitude increased from less than 50,000 in 2010 to about 250,000 in 2020. Researchers say this is partly due to an increase in the number of sensors, but it is estimated that the number of lightning strikes in the area has tripled in the past 10 years.

However, another global lightning detection network operated by Vaisala failed to capture this large increase. In 2012, Global Lightning Database 360 ??(GLD360) started operating, so their recording period was shorter than that of the Washington team, but the network was more sensitive and recorded more and weaker lightning.

Ryan Said, a research engineer at Vaisala, said that from 2012 to 2020, they did not record a significant increase in lightning activity; but this does not mean that this trend does not exist, just that scientists need to More time to observe to figure out changes in weather patterns.

"This is just the beginning," he said.

In recent years, Vaisala's Lightning Network has detected some unusual activity. In the summers of 2019 and 2020, GLD360 recorded more than 100 lightning events at 85 degrees north latitude, including a series of lightning events less than 555 kilometers away from the North Pole, which is extremely rare.

There may be more lightning in the future

Chen Yang said that regardless of whether these changes have already occurred, it is almost certain that climate change means that there will be more lightning in the Arctic.

Lightning requires special factors to form, and these are rare in the far north, but climate change may make them more common.

First, the air at the ground level must be warm, full of moisture, and able to float quickly. The temperature of the air above must be low enough that as the warm air rises rapidly, the moisture condenses into small ice particles. The whole system is very turbulent. The air is spinning and turbulent, and the ice particles are violently tumbling in it, causing electrons to collide with each other and the ice particles to be charged. Finally, a massive electrical discharge occurs inside the cloud, or between the cloud and the ground.

Historically, the cold, relatively stable atmosphere of the Arctic is not suitable for thunderstorms. But over the past 30 years, temperatures here have risen by 1 to 2 degrees, faster than anywhere else on Earth.

Yang Chen and his colleagues, including Veravebeke, want to know how many more lightning these changes in climate conditions will trigger by the end of the century. They compared Arctic lightning data recorded by satellites in the 1990s with weather data from the same period to find which atmospheric conditions best matched the rare lightning strikes.

Climate models predict conditions conducive to lightning, and by extension of lightning (which differs slightly from the overall likelihood of thunderstorms), they find that lightning will occur about 1.5 times more frequently in the tundra in the future. Nearly double that in boreal forest areas. The probability of lightning occurrence in the continental United States is expected to increase by 50%. In comparison, the number in the Arctic is much greater. Some studies suggest that total global lightning activity will decline by 2100, in part because lightning-prone tropical regions may heat up, reducing the frequency of ice crystal formation.

The satellite data Yang Chen and his colleagues used to estimate lightning did not match the ground-based network used to detect recent lightning activity, so the two results cannot be directly compared or integrated. But they all highlight "the growing importance of lightning in the Arctic," Veravebeke said.

But the most worrying thing is not the lightning itself, but its possible effects. Wildfires anywhere in the world release carbon stored in forests and soils. For example, the Australian wildfires in 2020 released more than 800 million tons of carbon dioxide, nearly 1.5 times the country's total annual emissions.

Wildfires don’t just burn wood on the ground. "Burning is three-dimensional," explains Michelle Mack, an ecologist and Arctic expert at Northern Arizona University. Beneath the surface flames, organic matter in the soil is also burned, and Arctic soils are much richer in carbon than soils elsewhere in the world. Carbon accumulated over decades is often found in the top ten centimeters. Arctic fires that devour topsoil would release at least twice as much carbon as California fires, Veravebeke said.

The study shows that by the end of the century, as more lightning sparks more fires, the Arctic will burn more area and release more carbon than today's average annual release from fires (about 3.4 million tons). More than 150%.

But it could be worse. The fires changed the ecosystem, opening up new space for forests and shrubs to grow, prompting them to move north. This in turn increases the likelihood of fires, as trees catch fire more easily than tundra.

Forests also warm and catch fire more easily than tundra because they are darker and absorb more sunlight. Chen Yang and colleagues found that if lightning-triggered fires increase and accelerate the migration of forests northward, carbon release will increase by 570% compared to now, releasing about 23 million tons of carbon dioxide into the atmosphere every year, equivalent to one-fifth of the California fires in 2020. one.

In this regard, the research team only gave an overview without detailed calculations: the permafrost area in the Arctic is 13 million square kilometers, and fires caused by lightning will also endanger the carbon-rich permafrost and accelerate melting , releasing large amounts of carbon stored in frozen soil. In other words, carbon emissions will increase by 570%. “This is only the lower limit of our estimate,” Chen Yang said.

(Translator: Sky4)