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(THE CONVERSATION) Alaska is on the verge of another historic year of wildfires, with its fastest start to the fire season on record. By mid-June 2022, over a million acres had burned. By early July, that number was well over 2 million acres, more than double the area of a typical Alaskan fire season.
Rick Thoman, a climate scientist at the International Arctic Research Center in Fairbanks, explains why Alaska is seeing so many large and intense fires this year and how the region’s fire season is changing.
Why is Alaska experiencing so many wildfires this year?
There is no simple answer.
At the start of the season, Southwest Alaska was one of the few areas in the state with lower than normal snowpack. Then we had a warm spring and Southwest Alaska dried up. An eruption of thunderstorms in late May and early June provided the spark.
Global warming has also increased the amount of fuels – plants and trees that are available to burn. More fuel means more intense fires.
So the weather factors – the warm spring, low snowpack, and unusual thunderstorm activity – combined with the decades-long warming that allowed vegetation to thrive in southwestern Alaska, together fuel a active fire season.
In interior Alaska, much of the region has been abnormally dry since late April. So, with the thunderstorms, it’s no surprise that we are now seeing a lot of fires in the area. The interior recorded around 18,000 strikes over two days in early July.
Are thunderstorms like this becoming more frequent?
That’s the million dollar question.
It’s actually a two-part question: Do thunderstorms happen more often now in places that rarely had them? I think the answer is an unequivocal “yes”. Is the total number of strikes increasing? We don’t know, because lightning strike tracking networks today are much more sensitive than in the past.
Thunderstorms in Alaska are different from those in most of the lower 48 in that they tend not to be associated with weather fronts. These are what meteorologists call air masses or pulsed thunderstorms. They are dictated by two factors: the humidity available in the lower atmosphere and the temperature difference between the lower and middle atmosphere.
In a warming world, the air can hold more moisture, which can cause intense storms. In the interior of Alaska, thunderstorms are more frequent. For example, the number of days with thunderstorms recorded at Fairbanks airport shows a marked increase. Aboriginal elders also agree that they see thunderstorms more often.
You mentioned hotter fires. How do forest fires evolve?
Wildfires are part of the natural ecosystem of the northern boreal, but the fires we have today are not the same as those that burned 150 years ago.
More fuel, more lightning strikes, higher temperatures, lower humidity – they combine to fuel fires that burn hotter and burn deeper into the ground, so rather than just burning trees and scorching undergrowth, they consume everything, and you are left with this lunar landscape of ashes.
Spruce trees that rely on fire to open their cones cannot reproduce when fire turns those cones to ashes. People who have been in the field fighting the fire for decades say they are 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 do these fires have on the population?
The most common impact on humans is smoke.
Most wildfires in Alaska do not burn in heavily populated areas, although they do occur. When you burn 2 million acres, you burn a lot of trees, and so you put a lot of smoke in the air, and it travels long distances.
In early July, we saw explosive wildfire activity north of Lake Iliamna in Southwest Alaska. Winds were blowing from the southeast at the time and dense smoke was carried for hundreds of kilometres. In Nome, 400 miles away, the hospital air quality index exceeded 600 parts per million for PM2.5, fine particles that can trigger asthma and damage the lungs. Anything over 150 ppm is unhealthy and over 400 ppm is considered dangerous.
There are other risks. When wildfires threaten rural Alaskan communities, as they did near St. Mary’s in June 2022, evacuation can mean evacuating people.
Worsening fire seasons have also put pressure on firefighting resources everywhere. Firefighting is expensive, and Alaska relies on fire crews, planes, and equipment from the lower 48 states and other countries. In the past, when Alaska had a big fire season, crews would come from the lower 48s because their fire season was usually much later. Now, the wildfire season is year-round, and there are fewer mobile resources available.
This article is republished from The Conversation under a Creative Commons license. Read the original article here: https://theconversation.com/alaska-on-fire-thousands-of-lightning-strikes-and-a-warming-climate-put-alaska-on-pace-for-another-historic – fire-season-186453.