Tundra fire increases the likelihood of methane hotspot formation in the Yukon–Kuskokwim Delta, Alaska, USA

Abstract

Rapid warming in Arctic tundra may lead to drier soils in summer and greater lightning ignition rates, likely culminating in enhanced wildfire risk. Increased wildfire frequency and intensity leads to greater conversion of permafrost carbon to greenhouse gas emissions. Here, we quantify the effect of recent tundra fires on the creation of methane (CH4) emission hotspots, a fingerprint of the permafrost carbon feedback. We utilized high-resolution (∼25 m2 pixels) and broad coverage (1780 km2) airborne imaging spectroscopy and maps of historical wildfire-burned areas to determine whether CH4 hotspots were more likely in areas burned within the last 50 years in the Yukon–Kuskokwim Delta, Alaska, USA. Our observations provide a unique observational constraint on CH4 dynamics, allowing us to map CH4 hotspots in relation to individual burn events, burn scar perimeters, and proximity to water. We find that CH4 hotspots are roughly 29% more likely on average in tundra that burned within the last 50 years compared to unburned areas and that this effect is nearly tripled along burn scar perimeters that are delineated by surface water features. Our results indicate that the changes following tundra fire favor the complex environmental conditions needed to generate CH4 emission hotspots. We conclude that enhanced CH4 emissions following tundra fire represent a positive feedback that will accelerate climate warming, tundra fire occurrence, and future permafrost carbon loss to the atmosphere.

Unrecorded Tundra Fires in Canada, 1986–2022

“…Yet, the region will likely see the continued thawing of permafrost, increased variability in rainfall, and shifting hydrology [4,62], and so the extent to which these myriad changes will interact and how burning will be impacted remains unknown. Moreover, given recent findings that tundra fire locations are more likely to become major methane sources [63], as a consequence of permafrost thaw, the climate implications of increased fire activity are vital to understand. Regardless of the pattern or trend in future burning, accurate historical mapping of Arctic and sub-Arctic fires is a critical first step to understand potential changes in fire regimes.…”