Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

Abstract. Trends in the atmospheric concentration of CO₂ during three recent interglacials – the Holocene, the Eemian and Marine Isotope Stage (MIS) 11 – are investigated using an earth system model of intermediate complexity, which we extended with process-based modules to consider two slow carbon cycle processes – peat accumulation and shallow-water CaCO₃ sedimentation (coral reef formation). For all three interglacials, model simulations considering peat accumulation and shallow-water CaCO₃ sedimentation substantially improve the agreement between model results and ice core CO₂ reconstructions in comparison to a carbon cycle set-up neglecting these processes. This enables us to model the trends in atmospheric CO₂, with modelled trends similar to the ice core data, forcing the model only with orbital and sea level changes. During the Holocene, anthropogenic CO₂ emissions are required to match the observed rise in atmospheric CO₂ after 3 ka BP but are not relevant before this time. Our model experiments show a considerable improvement in the modelled CO₂ trends by the inclusion of the slow carbon cycle processes, allowing us to explain the CO₂ evolution during the Holocene and two recent interglacials consistently using an identical model set-up.