The Influence of Arctic Tundra Fires on Methane Hotspot Distribution in the Yukon-Kuskokwim Delta, Alaska

Abstract:

The Arctic has experienced dramatic climate-induced changes that have significant implications for current and future global climate change. However, some of the specific drivers and dynamics in this region remain poorly understood. Climate warming has led to increased thawing of permafrost that may in turn give rise to elevated methane (CH₄) emissions, accelerating a positive permafrost-carbon feedback. Increases in the frequency and severity of fires also observed in the region may further amplify this climate feedback. In this study, we provide a unique, process-level analysis of the potential influence of fires on elevated CH₄ emission hotspots in the tundra of the Yukon-Kuskokwim Delta (YKD), Alaska, a subarctic discontinuous permafrost region scattered with lakes, ponds and wetlands. We used a new airborne dataset developed by Elder et al. (2020) of high-resolution spectroscopy (AVIRIS-NG) acquired during a 2018 survey that revealed the spatial distribution patterns of CH₄ hotspots over the entire Arctic-Boreal Vulnerability Experiment (ABoVE) domain (~100,000 km² of surveyed area or roughly 3 billion individual pixels). We replicated the hotspot signature for a YKD subset of the AVIRIS-NG dataset (~1,400 km² or roughly 23,000 individual pixels). Hotspots were then analyzed in conjunction with geospatial data layers (i.e., Alaska fire history) to assess potential drivers of the observed patterns. Preliminary results showed that burned areas consistently had a higher ratio of hotspots than unburned areas across all flight lines, where hotspots within recent fire events exhibited a greater frequency than those in historic events. The highest ratio of hotspots was within 40m of burn scars, and additional research is being conducted to assess the influence of adjacent water features on these results in keeping with the water dependence pattern demonstrated by Elder et al. (2020). Our preliminary results suggest that Arctic tundra fires are an important driver of CH₄ dynamics in the region, with recent burn scar areas exerting a particularly strong influence on CH₄ hotspot distribution. Future research should extend to different bioclimatic subzones to explore inter-regional variability addressing scaling issues associated with Arctic CH₄ emissions, from site to regional scales.