Thoman: Rising temp, lightning strikes ramp up fire threat in Alaska

Alaska is on pace for another historic wildfire year, with its fastest fire season start on record.

By mid-June 2022, over 1 million acres had burned. By early July, that number was well over 2 million acres, more than twice the size of a typical Alaska fire season.

So why is Alaska seeing so many fires this year? Several factors are at work.

Early in the season, hard-hit southwest Alaska experienced a below normal snowpack. Then a warm spring descended, drying out the land. Finally, an outbreak of thunderstorms in late May and early June provided the spark to set it ablaze.

Global warming has also increased the amount of fuel — trees and shrubs that are available to burn in Alaska’s vast interior. More fuel means more intense fires.

At the International Arctic Research Center in Fairbanks, where I serve as a climate specialist, our research indicates climate factors — low snowpack, warm spring and heavy thunderstorm activity — combined with global warming factors — decades of increasingly thick vegetation — to fuel an alarmingly active fire season.

This year’s season has gotten off to a start matching that of record-setting season of 2015 and exceeding those of all other big fire seasons.

The Alaskan interior has been abnormally dry since late April. So, with the lightning storms, it’s no surprise we’re now seeing many fires in the region. The interior had about 18,000 strikes over two days in early July alone.

Are lightning storms like this becoming more frequent? That’s a million-dollar question.

It’s actually a two-part question:

Are thunderstorms occurring more often now in places that used to rarely get them? I think the answer is unequivocally “yes.”

Is the total number of strikes increasing? We don’t know, because the networks tracking lightning strikes today are far more sensitive than those of the past.

Thunderstorms in Alaska differ from those in most of the lower 48, as they don’t tend to be associated with weather fronts meteorologists call air mass or pulse thunderstorms.

They’re driven by two factors: the available moisture in the lower atmosphere and the temperature difference between the lower and middle atmospheres.

In a warming world, air can hold more moisture, so you can get intense storms. So in interior Alaska, we’re getting thunderstorms more frequently.

Fire intensity is also increasing. Wildfire is part of the natural ecosystem in the Boreal north, but the fires we’re getting now are not the same as the fires that were burning 150 years ago.

More fuel, more lightning strikes, higher temperatures and lower humidity combine to fuel fires that burn hotter and deeper. Rather than just scorching the trees and burning through undergrowth, they’re consuming everything, leaving a moonscape of ash.

Spruce trees that rely on fire to burst open their cones can’t reproduce when the fire turns those cones to ash. People who have been out in the field fighting fire for decades say they’re amazed at the amount of destruction they see now.

So while fire has been natural here for tens of thousands of years, the fire situation has changed. The frequency of million-acre fires in Alaska has doubled since before 1990.

What impact are these fires having on the population? The most common impact on humans is smoke.

Most wildfires in Alaska aren’t burning through heavily populated areas, though that does happen. When you’re burning 2 million acres, you’re burning a lot of trees. That means you’re putting a lot of smoke into the air, and it travels long distances.

In early July, we saw explosive wildfire activity north of Lake Iliamna in southwest Alaska. The winds were blowing from the southeast then, and dense smoke was transported hundreds of miles.

In Nome, 400 miles away, the air quality index at the hospital exceeded 600 parts per million for fine particulate matter that can trigger asthma. Anything over 150 ppm is considered unhealthy anything over 400 ppm is considered hazardous.

There are other risks as well. When fires threaten rural Alaskan communities, as one did near St. Mary’s in June, evacuating can mean flying people out.

Worsening fire seasons also put pressure on firefighting resources.

Alaska counts on fire crews, planes and equipment from the lower 48.

In the past, when Alaska had a big fire season, crews would come up from the lower 48 because their fire season didn’t typically arrive until much later. Now, wildfire season in the continental U.S. essentially runs all year, leaving fewer resources available.

From The Conversation, an online repository of lay versions of academic research findings found at https://theconversation.com/us. Used with permission.