Recent tundra fires 'exceed anything in past 3,000 years'

Recent tundra fires 'exceed anything in past 3,000 years'

Wildfires on Alaska's North Slope were more active this past century than at any time in the past 3,000 years, according to a study recently publishedin the journal Biogeosciences.

The study was conducted in Arctic Alaska by an international team of researchers from Germany, Poland, the United Kingdom, Romania and the University of Alaska Fairbanks' Toolik Field Station.

Angelica Feurdean, the study's lead author and a senior researcher at Goethe University in Germany, said the team took a multidisciplinary approach to reconstructing fire history. Their findings point to record-high activity caused by increasing woody plants and drying soils, two consequences of warming temperatures.

"The interlinked changes across millennia mean recent fires are indicators of a system undergoing rapid transformation," Feurdean said.

To reconstruct wildfire activity, the team cored half a meter into tundra peat soils at nine sites north of the Brooks Range, along the Dalton Highway between Toolik Lake and the Franklin Bluffs.

Buried within each layer of the core were charcoal, pollen and pieces of dead plants and microbes. Feurdean and her colleagues measured the amounts of these materials within cores and used radiocarbon and lead dating to determine the ages of these layers. Together, these measurements painted a picture of past fire activity, dominant vegetation and moisture conditions.

Material from the peat cores dated back 3,000 years to around 1000 B.C. Charcoal records indicated fire activity was low for the first 2,000 years. Activity rose slightly between roughly A.D. 1000 and 1200 when tundra soils started to dry. But it dropped back to lower levels for the next seven centuries.

Then, in 1900, fire activity began to heat up again. By 1950, fire activity spiked to unprecedented levels as peat reached record dryness and woody shrubs increased. Fire activity rose and soils continued to dry through 2015, when the cores were taken.

The scientists then compared ancient fire history with that of modern activity by pairing charcoal remnants with satellite records.

Satellite records confirmed the evidence from charcoal records that fire activity has been rising since the latter half of the 20thcentury. Specifically, the late 1960s, 1990 and 2000s-2010s saw frequent fires.

Randy Fulweber, study co-author and the geographic information systems and remote sensing manager at UAF's Toolik Field Station, said combining the charcoal and satellite records also brought new insights into the severity of modern-day fires.

Evidence from recent large fires, Fulweber said "may be indicative of these fires burning hotter, consuming more fuel and leaving behind less charcoal."

"It may suggest a shifting fire regime, one in which fires are really burning hot," he said.

Fulweber credits this finding to the collaborative atmosphere at Toolik Field Station, which enabled the team to merge their expertise in paleoecology, GIS and remote sensing.

"There's something unique that a field station like Toolik provides in terms of the breadth and depth of specialties that helps studies like this happen and, ultimately, opens up more scientific questions to answer," Fulweber said.

ADDITIONAL CONTACT:Angelica Feurdean, [email protected]

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