Melting arctic sea ice helps drive worsening wildfires in West
Wildfires in the American West have grown more frequent and severe over recent decades.
New research in the journal Nature Communications suggests changes in arctic sea ice might bear part of the blame.
By pairing more advanced computer models with observations and sensitivity experiments, the authors drew a stronger causal link between arctic conditions and wildfires in the western U.S. than was previously possible.
"We were able to get a mechanistic understanding of this teleconnection between decreasing arctic sea ice and the worsening regional fire weather over western U.S.," said co-author Hailong Wang of the Paciﬁc Northwest National Laboratory in Richland, Washington.
The modeling study found that sea ice melt from July to October shifts the polar jet stream north and alters regional atmospheric circulation, creating hotter, drier conditions out West and the increasing probability of large wildfires the following September to December.
"We're able to understand, step by step, how the arctic sea ice reduction would affect the circulation, and how the atmospheric circulation affects the pressure system over western U.S., and how the pressure system will bring dry air dry and hot air to the area and reduce precipitation," said Wang.
Wang and his colleagues found the effect was on par with that of the tropical El Niño Southern Oscillation, which also exerts an influence on regional wildfire conditions.
Wang said that's bad news if, as predicted, arctic sea ice continues declining.
"If we believe the model predictions of ice-free by the midcentury, we will anticipate more dramatic changes in every aspect of the climate system, including the risks for wildfires, not just over western U.S. It could be anywhere else."