On July 16 of 2010 a lightning strike caused the Anaktuvuk River Fire which ended up burning more than a thousand square kilometres of tundra on Alaska’s North Slope, and burning through to the end of September by which time nearby lakes had already frozen over.
After hearing about the Anaktuvuk River Fire, University of Illinois plant biology professor Feng Sheng Hu headed to the region to find whether the fire was one in a number of historical events or was an anomaly.
“If such fires occur every 200 years or every 500 years, it’s a natural event,” Hu said. “But another possibility is that these are truly unprecedented events caused by, say, greenhouse warming.”
Hu’s team studied collected sediment cores and found that there was no evidence of a fire of similar scale and intensity over the past 5,000 years. They then went on to study 60 years of fire in an attempt to determine whether specific climate conditions linked with fires.
What they found was a striking pattern, according to Hu. “There is a dramatic, nonlinear relationship between climate conditions and tundra fires, and what one may call a tipping point,” he said. Once the temperature rises above a mean threshold of 10 degrees Celsius (50 degrees Fahrenheit) in the June-through-September time period, he said, “the tundra is just going to burn more frequently.”
Over the 60 years studied the team found that temperatures during the regions warm season fluctuated between 6 and 9 degrees Celsius (42.8 to 48.2 degrees Fahrenheit). However from 1995 onwards these temperatures trended upwards resulting in a mean temperature in 2007 of 11.1, a record for the region, which also saw soil moisture and precipitation drop to an all-time low.
Source: University of Illinois at Urbana-Champaign
Image Source: Bureau of Land Management