| Summary: | This publication contains code and data of a biogeochemistry model, XPTEM-XHAM, that includes microbial dynamics of high-affinity methanotrophs (HAM) and methanogens with permafrost carbon dynamics. You will find 4 zipped files when downloading the bundle. One file (Code_XPTEM-XHAM.zip) contains C++ codes, compiler, and guidelines for the XPTEM-XHAM model. Other three files (Data_XPTEM_XHAM_2000_2016.zip, Data_XPTEM_XHAM_2017_2100_default. zip, and Data_XPTEM_XHAM_2017_2100_w_Physiology. zip) contain raw and processed model results for contemporary period (2000-2016) and future projections (2017-2100), and Matlab files to plot the processed data in Matlab. 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. However, this methane source might have been overestimated without considering high affinity methanotrophs (HAM, methane oxidizing bacteria) recently identified in Arctic mineral soils. Here, we find that HAM dynamics double the upland methane sink (~5.5 TgCH4yr-1) north of 50°N in simulations from 2000-2016 by integrating the dynamics of HAM and methanogens into a biogeochemistry model that includes permafrost SOC dynamics. The increase is equivalent to at least half of the difference in net methane emissions estimated between process-based models and observation-based inversions, and the revised estimates better match site-level and regional observations. The new model projects doubled wetland methane emissions between 2017-2100 due to more accessible permafrost carbon. 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 TgCH4yr-1). The projected net methane emissions may decrease further due to different physiological responses between HAM and methanogens in response to increasing temperature.
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