Concurrent increases in winter precipitation and summer wildfire risk in a warming Alaska

Abstract

Alaska is experiencing simultaneous trends of increased winter wetness and heightened summer fire risk due to global warming, leading to more frequent wildfires and greater unpredictability in fire behavior in recent decades. Large-ensemble simulations show that warming drives distinct seasonal changes: in winter, an intensified ridge over the western U.S. enhances moisture transport to Alaska, increasing precipitation while promoting vegetation growth near the Alaska Range. In summer, rising temperatures intensify the fire weather index signaling greater wildfire potential and increase lightning activity. Although the links among these complex seasonal changes remain difficult to validate, temporal overlap-enhanced vegetation growth followed by more fire-conducive weather, and associated increase in lightning could collectively heighten wildfire risk. The robustness of our large-ensemble simulations provides compelling evidence for these cascading effects. Extreme lightning-driven events, such as the Swan Lake Fire, represent the emerging pattern in Alaska's evolving fire regime. The concurrent rise in winter wetness and summer fire conditions underscore the urgent need for adaptive fire management strategies that address these interconnected climate drivers.