Effects of permafrost thaw on CO2 and CH4 exchange in a western Alaska peatland chronosequence

Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH₄), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO₂) and CH₄ exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH₄exchange in July (123 ± 71 mg CH₄–C m⁻² d⁻¹) was observed in features that have been thawed for 30 to 70 (