An active atmospheric methane sink in high Arctic mineral cryosols.

Methane (CH₄) emission by carbon-rich cryosols at the high latitudes in Northern Hemisphere has been studied extensively. In contrast, data on the CH₄ emission potential of carbon-poor cryosols is limited, despite their spatial predominance. This work employs CH₄ flux measurements in the field and under laboratory conditions to show that the mineral cryosols at Axel Heiberg Island in the Canadian high Arctic consistently consume atmospheric CH₄. Omics analyses present the first molecular evidence of active atmospheric CH₄-oxidizing bacteria (atmMOB) in permafrost-affected cryosols, with the prevalent atmMOB genotype in our acidic mineral cryosols being closely related to Upland Soil Cluster α. The atmospheric (atm) CH₄ uptake at the study site increases with ground temperature between 0 °C and 18 °C. Consequently, the atm CH₄ sink strength is predicted to increase by a factor of 5-30 as the Arctic warms by 5-15 °C over a century. We demonstrate that acidic mineral cryosols are a previously unrecognized potential of CH₄ sink that requires further investigation to determine its potential impact on larger scales. This study also calls attention to the poleward distribution of atmMOB, as well as to the potential influence of microbial atm CH₄ oxidation, in the context of regional CH₄ flux models and global warming. [ABSTRACT FROM AUTHOR]