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

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 dynamics³ leads to the upland methane sink doubling (~5.5 Tg CH₄ 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 CH₄ 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.