2023-11-01 NASA
◆火災が凍土を融解させ、湖や湿地周辺の土壌で古い炭素がメタンガスに変換されるため、火災が起きたツンドラ地帯でメタンの「ホットスポット」が発生し、気候変動を加速し、ツンドラでの火災の発生頻度を増加させる可能性があります。火災が凍土に及んだ場合、土壌の変化が生態系に長期的な影響を及ぼすため、高緯度地域での火災増加が世界の気候にどのように影響するかについてさらなる研究が必要です。
＜関連情報＞
- https://www.nasa.gov/earth/nasa-flights-link-methane-plumes-to-tundra-fires-in-western-alaska/
- https://iopscience.iop.org/article/10.1088/1748-9326/acf50b
米国アラスカ州ユーコン・クスコクウィム・デルタにおけるメタンホットスポット形成の可能性を高めるツンドラ火災 Tundra fire increases the likelihood of methane hotspot formation in the Yukon–Kuskokwim Delta, Alaska, USA
Elizabeth Yoseph, Elizabeth Hoy, Clayton D Elder, Sarah M Ludwig, David R Thompson and Charles E Miller
Environmental Research Letters Published 9 October 2023
DOI:10.1088/1748-9326/acf50b
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.
