GeoChip data from depth-stratified soil samples across 9-year winter warming plots at CiPEHR site

Arctic permafrost stores nearly half of global soil carbon. Thawing releases CO₂ and CH₄, with CH₄ having higher warming potential—making their relative temperature sensitivity (EM/C) critical for feedback projections. A nine-year winter warming experiment (+0.8–1.2°C) in Alaska revealed that even slight warming shifted EM/C from negative to positive, increasing CH₄ emissions by 62%. This shift was driven primarily by microbial changes in the permafrost-active layer transition zone (35–55 cm), where methanogens increased and methanotrophs decreased, identifying a "methane amplification hotspot." These results underscore the need to integrate depth-resolved microbial dynamics into models to improve predictions of permafrost-carbon feedback.