Rapid Early Development of Circumarctic Peatlands and Atmospheric CH4 and CO2 Variations

An analysis of 1516 radiocarbon dates demonstrates that the development of the current circumarctic peatlands began ~16.5 thousand years ago (ka) and expanded explosively between 12 and 8 ka in concert with high summer insolation and increasing temperatures. Their rapid development contributed to the sustained peak in CH₄ and modest decline of CO₂ during the early Holocene and likely contributed to CH₄ and CO₂ fluctuations during earlier interglacial and interstadial transitions. Given the decreased tempo of peatland initiation in the late Holocene and the transition of many from fens (which generated high levels of CH₄) to ombrotrophic bogs, a neoglacial expansion of northern peatlands cannot explain the increase in atmospheric CH₄ that occurred after 6 ka.