Cold season emissions dominate the Arctic tundra methane budget

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Zona, Donatella, Gioli, Beniamino, Commane, Róisín, Lindaas, Jakob, Wofsy, Steven C., Miller, Charles E., Dinardo, Steven J., Dengel, Sigrid, Sweeney, Colm, Karion, Anna, Chang, Rachel Y. -W., Henderson, John M., Murphy, Patrick C., Goodrich, Jordan P., Moreaux, Virginie, Liljedahl, Anna, Watts, Jennifer D., Kimball, John S., Lipson, David A., Oechel, Walter C.
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic; Tundra
• Online Access: http://www.osti.gov/servlets/purl/1348836; https://www.osti.gov/biblio/1348836; https://doi.org/10.1073/pnas.1516017113

Arctic terrestrial ecosystems are major global sources of methane (CH 4 ); hence, it is important to understand the seasonal and climatic controls on CH 4 emissions from these systems. Here, we report year-round CH 4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH 4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH 4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH 4 derived from aircraft data demonstrate the large spatial extent of late season CH 4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH 4 y –1 , ~25% of global emissions from extratropical wetlands, or ~6% of total global wetland methane emissions. Here, the dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH 4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.