Permafrost carbon feedback (PCF) modeling has focused on gradual thaw of near-surface permafrost leading to enhanced carbon dioxide and methane emissions that accelerate global climate warming. These state-of-the-art land models have yet to incorporate deeper, abrupt thaw in the PCF. Here we use model data, supported by field observations, radiocarbon dating, and remote sensing, to show that methane and carbon dioxide emissions from abrupt thaw beneath thermokarst lakes will more than double radiative forcing from circumpolar permafrost-soil carbon fluxes this century. Abrupt thaw lake emissions are similar under moderate and high representative concentration pathways (RCP4.5 and RCP8.5), but their relative contribution to the PCF is much larger under the moderate warming scenario. Abrupt thaw accelerates mobilization of deeply frozen, ancient carbon, increasing 14C-depleted permafrost soil carbon emissions by ~125-190% compared to gradual thaw alone. These findings demonstrate the need to incorporate abrupt thaw processes in earth system models for more comprehensive projection of the PCF this century.
Notes
Cites: Philos Trans A Math Phys Eng Sci. 2015 Nov 13;373(2054):null PMID 26438276
Cites: Geophys Res Lett. 2013 Dec 16;40(23):6165-6170 PMID 26074633
Cites: Science. 2006 Jun 16;312(5780):1612-3 PMID 16778046
Cites: Nature. 2018 Jan 31;554(7690):92-96 PMID 29388952
Cites: Nat Commun. 2016 Oct 11;7:13043 PMID 27725633