Climate Watch

By Rick Thoman Alaska Climate Specialist Alaska Center for Climate Assessment and Policy International Arctic Research Center/University of Alaska Fairbanks

St. Mary’s and neighboring communities have been threatened by the East Fork fire, which is by far the largest documented wildfire to burn in predominantly tundra environment in the Yukon-Kuskokwim Delta region. The fire was started by lightning on May 31 more than 20 miles north of St. Mary’s, but the combination of early snow melt, far below normal rainfall, very warm temperatures and persistent north to northeast winds pushed the fire east across the Andreafsky River and south toward the Yukon. Fires need fuel to keep burning, and like in much of western Alaska, elders report that tundra vegetation is much larger and thicker than it was in the 20th century, which means there’s much more fuel to burn once fire is on the ground. More fuel means hotter fires, which allows for deeper burning and is more difficult to extinguish.

Smoke from the East Fork fire, and other fires burning in southwest Alaska, have been evident in many parts of western Alaska. The Seward Peninsula and eastern Norton Sound are no stranger to wildfire. Fires were common during the Gold Rush Era, often intentionally set by miners as a way to do quick land clearing. The Alaska Fire Service has devoted considerable time and resources to documenting post-World War Two wildfires around the state, so we have a reasonably good inventory at least for larger fires.

It turns out that the largest tundra wildfire on record in Alaska was the Imuruk Basin wildfire that was started by lightning in June 1954. The fire burned near 650 square miles, and some of this same area burned again in 1971. The hot dry summer of 1977 was another big year for wildfire on the Seward Peninsula and the Northwest Arctic Borough, too.

As the graphic shows, wildfires over the past 70 years are not evenly distributed around the Seward Peninsula and eastern Norton Sound.

Rather, fires are strongly favored to the north of the mountains. These areas tend to receive less winter snow and have less cool, rainy weather in the summer. The much wetter and snowier south side of the mountains, including the area north of Nome, have no recent history of any large fires. The situation is more complicated on the eastern Seward Peninsula because of the spruce forest, which is especially flammable.

Another area that has not had much wildfire in the past 70 years is the west side of the Nulato Hills, east of Shaktoolik and Unalakleet. These areas often have relatively low snowpack and thunderstorms occur in these areas. It may be just happenstance that there has not been a big fire in this region, or it may be that there is a frequent enough cooling sea breeze that fires that start don’t have a chance to grow big before the cooler and more humid marine air from Norton Sound arrives.