Amount and timing of permafrost carbon release in response to climate warming

TLDR

The thaw and release of carbon currently frozen in permafrost will increase atmospheric CO₂ concentrations and amplify surface warming, initiating a positive permafrost carbon feedback on climate. The study estimates the strength and timing of the permafrost carbon feedback using surface weather from three global climate models under the A1B scenario and the SiBCASA land surface model. It applies the SiBCASA model to simulate permafrost carbon fluxes driven by the modeled climate inputs. By 2200, permafrost area will shrink 29–59 %, active layer thickness will rise 53–97 cm, and cumulative carbon flux will reach 190 ± 64 Gt C, enough to shift the Arctic from a carbon sink to a source after the mid‑2020s, offset 42–88 % of the global land sink, and require larger fossil‑fuel reductions to meet CO₂ targets. DOI: 10.1111/j.1600-0889.2011.00527.x.

Abstract

The thaw and release of carbon currently frozen in permafrost will increase atmospheric CO 2 concentrations and amplify surface warming to initiate a positive permafrost carbon feedback (PCF) on climate. We use surface weather from three global climate models based on the moderate warming, A1B Intergovernmental Panel on Climate Change emissions scenario and the SiBCASA land surface model to estimate the strength and timing of the PCF and associated uncertainty. By 2200, we predict a 29–59% decrease in permafrost area and a 53–97 cm increase in active layer thickness. By 2200, the PCF strength in terms of cumulative permafrost carbon flux to the atmosphere is 190 ± 64 Gt C. This estimate may be low because it does not account for amplified surface warming due to the PCF itself and excludes some discontinuous permafrost regions where SiBCASA did not simulate permafrost. We predict that the PCF will change the arctic from a carbon sink to a source after the mid-2020s and is strong enough to cancel 42–88% of the total global land sink. The thaw and decay of permafrost carbon is irreversible and accounting for the PCF will require larger reductions in fossil fuel emissions to reach a target atmospheric CO 2 concentration. DOI: 10.1111/j.1600-0889.2011.00527.x