Reduced net methane emissions due to microbial methane oxidation in a warmer Arctic

• Published in: Nature climate change Vol. 10; no. 4; pp. 317 - 321
• Main Authors: Oh, Youmi, Zhuang, Qianlai, Liu, Licheng, Welp, Lisa R., Lau, Maggie C. Y., Onstott, Tullis C., Medvigy, David, Bruhwiler, Lori, Dlugokencky, Edward J., Hugelius, Gustaf, D’Imperio, Ludovica, Elberling, Bo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2020; Nature Publishing Group
• Subjects: 704/106; 704/47; Affinity; Atmospheric methane; Atmospheric models; Biogeochemistry; Climate Change; Climate Change/Climate Change Impacts; Computer simulation; Dynamics; Earth and Environmental Science; Emissions; Environment; Environmental Law/Policy/Ecojustice; Letter; Methane; Methane budget; Methane emissions; Methanogenic bacteria; Methanotrophic bacteria; Microorganisms; Organic carbon; Organic soils; Oxidation; Permafrost; Physiological responses; Soil; Soil dynamics; Wetlands; Arctic region
• ISSN: 1758-678X; 1758-6798; 1758-6798
• DOI: 10.1038/s41558-020-0734-z

Methane emissions from organic-rich soils in the Arctic have been extensively studied due to their potential to increase the atmospheric methane burden as permafrost thaws 1 – 3 . However, this methane source might have been overestimated without considering high-affinity methanotrophs (HAMs; methane-oxidizing bacteria) recently identified in Arctic mineral soils 4 – 7 . Herein we find that integrating the dynamics of HAMs and methanogens into a biogeochemistry model 8 – 10 that includes permafrost soil organic carbon dynamics 3 leads to the upland methane sink doubling (~5.5 Tg CH 4  yr −1 ) north of 50 °N in simulations from 2000–2016. The increase is equivalent to at least half of the difference in net methane emissions estimated between process-based models and observation-based inversions 11 , 12 , and the revised estimates better match site-level and regional observations 5 , 7 , 13 – 15 . The new model projects doubled wetland methane emissions between 2017–2100 due to more accessible permafrost carbon 16 – 18 . However, most of the increase in wetland emissions is offset by a concordant increase in the upland sink, leading to only an 18% increase in net methane emission (from 29 to 35 Tg CH 4  yr −1 ). The projected net methane emissions may decrease further due to different physiological responses between HAMs and methanogens in response to increasing temperature 19 , 20 . Models overestimate Arctic methane emissions compared to observations. Incorporating microbial dynamics into biogeochemistry models helps reconcile this discrepancy; high-affinity methanotrophs are an important part of the Arctic methane budget and double previous estimates of methane sinks.