Wildfires ‘speeding permafrost collapse in Arctic Alaska’

Frozen ground’s disintegration could lead to an outpouring of carbon stored in it, writes Sam Hancock

This file photo from 2019 shows melting ice beside severe erosion of the permafrost tundra at Bethel on the Yukon Delta in Alaska (AFP via Getty Images)

Wildfires are contributing to the already devastating impact that climate change is having on the decline of carbon-filled permafrost in Arctic Alaska, a new study has found.

The report – conducted by researchers at the University of Illinois (UoI) in the US – shows that wildfires or tundra fires have accelerated the decline of frozen environments in a phenomenon known as ‘thermokarst’: the abrupt collapse of ice-rich permafrost as a result of thawing.

Permafrost is ground that continuously remains below 0C for two or more years, with scientists adding that Arctic permafrost specifically is considered a “storehouse” of frozen plant and animal matter.

Its degradation is an issue because, if thawed and degraded too much, it could release enough carbon to more than double that already in the atmosphere.

The study, which analysed 70 years’ worth of data, was published in the journal One Earth and found that the process of thermokarst has accelerated by 60 per cent in different regions of Arctic Alaska since the 1950s – as the climate crisis has worsened.

It is the first analysis of its kind to calculate the role of fire on permafrost integrity over so many decades, according to the researchers.

“[Thermokarst], because it’s very unpredictable, is poorly understood,” said Yaping Chen, a former graduate student at the UoI, who led the research with Mark Lara, a UoI professor of plant biology and of geography, and Feng Sheng Hu, a UoI professor of plant biology.

“With this study, we’re advancing our understanding of the permafrost ecosystem,” Ms Chen added.

The team analysed seven decades of air and satellite imagery to calculate the rate of “thermokarst formation” in different Alaskan areas.

Researchers also used machine-learning-based modelling to determine the relative contributions of climate change, fire disturbance and landscape features to observe permafrost declines.

After it was discovered that thermokarst increased by more than 50 per cent in less than 100 years, Ms Chen said that, while climate change is the “main driver” of its acceleration, “fire played a disproportionately large role in that process”.

This file photo from 2019 shows an aerial view of melting permafrost tundra and lakes near the Yupik Eskimo village, of Quinhagak, on the Yukon Delta in Alaska (AFP via Getty Images)

“Fire burned only 3 per cent of the Arctic landscape in that time period, but was responsible for more than 10 per cent of thermokarst formation,” she added.

Repeated fires in the same areas continued to damage the tundra but did not further accelerate thermokarst formation, the researchers found.

The study also revealed that a single fire could accelerate thermokarst formation for several decades.

“Models predict that thermokarst will only increase with climate change,” Prof Lara said. “In addition to thawing permafrost, climate warming dries out the tundra, increasing its flammability.

“This makes it more likely that lightning strikes will spark fires, causing even more permafrost degradation.”

Thawing and collapsing permafrost also leads to other landscape changes, Mr Lara said, giving the example that lakes sitting in frozen permafrost depressions may drain “when that permafrost degrades”.

“The loss of permafrost can open up the floodgates of environmental change,” he said, in what seemed to be a warning about the potential outpouring of carbon its ruin could cause.