Wildfires Increase Rate Of Permafrost Thaw In Arctic Tundra, Researchers Say

Years after the Anaktuvuk River fire – the largest recorded Arctic tundra fire – researchers led by the U.S. Geological Survey have found a link between wildfires in the Arctic tundra and widespread permafrost thaw.

In 2007, the massive Anaktuvuk River fire burned 1,000 square kilometers of tundra located along Alaska's North Slope. Using aerial data, researchers found permafrost thaw in about a third of the fire's wake – significant percentage when compared to the one percent found in undisturbed areas.   

Arctic tundra forests are found in the Northern Hemisphere and are characterized by extremely low temperatures, little precipitation, poor nutrients and short growing seasons.

"Once you burn off that protective layer, what we observed is the effect isn't immediate but takes a few years to really get going," Christopher Arp, co-author of the study and an assistant professor at the University of Alaska Fairbanks, explained in a news release.

Since wildfires are more common in boreal forests, the occurrence of permafrost loss in these areas is better documented. However, tundra fires are less common and their impact has not been studied in as much detail, until now.

For their study, researchers used a laser mapping technique called lidar, which allowed them to record thawing rates during repeated flyovers of the area two and seven years after the Anaktuvuk River fire. Researchers then created detailed topographic models of the burned area, which revealed irregular landscapes such as slumping hillsides and surface depressions.  

Using these observations, researchers measured changes in the land surface over time and predicted how the area's hydrology and vegetation would also be affected over time. Understanding such changes is important because frozen soils and peatlands of the Arctic tundra store vast amounts of carbon, researchers explained.    

In a previous study, scientists from the University of Alaska Fairbanks found that the Anaktuvuk River fire released 50 years' worth of carbon storage from the tundra forest into the atmosphere. Essentially, when permafrost thaws, the organic material in the soil decomposes and releases greenhouse gases, associated with climate change.

Permafrost is the foundation of Arctic landscapes, Arp added. As a result, dramatic changes such as melting are notable and can have vast impacts on surrounding wildlife.

The study was recently published in the journal Scientific Reports.

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