Trends in Alaskan Wildfires and Climate, 1950-2014

Abstract:

Since the 1970s, average temperatures in Alaska have warmed at nearly double the rate as in the continental U.S. Given the potential influence of warming temperatures on wildfire activity, we set out to investigate long-term wildfires trends in Alaska and how they correlate to climate changes in the region. We analyzed the frequency and area burned on public lands by large (>1,000 acres) wildfires in Alaska over the time period 1950-2014. This analysis considered wildfire statewide and also on sub-regional levels. Over the period, the average number of wildfires each year has increased. The decadal average number of large wildfires each year shows a pronounced increase beginning in the 1990s with a doubling over the most recent two and a half decades compared to the first four. The area burned by all large wildfires shows no discernible trend, but removing the very large wildfires (> 50,000 acres) shows and overall increase in recent decades. The wildfire season in Alaska is now 40 percent longer overall than at the beginning of the study period. One sub-regional result is the Arctic region of Alaska appears to be experiencing an emerging large wildfire regime in recent decades that had been absent for perhaps thousands of years. We also look at the correlations between relevant climate factors (annual and sub-annual), such as temperature, precipitation, and Pacific Decadal Oscillation phase and wildfire behavior. Finally, we look at the wildfire trend dependence on choice of time frame and other wildfire data products, such as Monitoring Trends in Burn Severity (MTBS) that began in 1984.