Landscape drying associated with permafrost thaw is expected to enhance
microbial methane oxidation in arctic soils. Here we show that ice-rich,
Yedoma permafrost deposits, comprising a disproportionately large fraction
of pan-arctic soil carbon, present an alternate trajectory. Field and laboratory
observations indicate that talik (perennially thawed soils in permafrost)
development in unsaturated Yedoma uplands leads to unexpectedly large
methane emissions (35–78 mg m−2 d−1 summer, 150–180 mg m−2 d−1 winter).
Upland Yedoma talik emissions were nearly three times higher annually than
northern-wetland emissions on an areal basis. Approximately 70% emissions
occurred in winter, when surface-soil freezing abated methanotrophy,
enhancing methane escape from the talik. Remote sensing and numerical
modeling indicate the potential for widespread upland talik formation across
the pan-arctic Yedoma domain during the 21st and 22nd centuries. Contrary to
current climate model predictions, these findings imply a positive and much
larger permafrost-methane-climate feedback for upland Yedoma.
