Modeling the dynamics of terrestrial carbon storage since the Last Glacial Maximum

Abstract

A dynamic global vegetation model (DGVM) was used to simulate global terrestrial carbon storage and stable carbon isotope composition changes for the last 21000 years. A paleoclimate scenario was provided by interpolation of coupled AGCM/mixed-layer ocean model experiments; [CO2]atm data were obtained from the Byrd and Taylor Dome ice core records. According to the model results, terrestrial carbon storage at the Last Glacial Maximum (LGM, 21 ka) was 821 Pg C less than today. The modeled isotopic composition (δ13C) of total terrestrial carbon at LGM was enriched by 1.5‰ compared to present. During the deglaciation (17-9 ka), vegetation expanded rapidly into formerly glaciated areas and carbon storage correspondingly increased. Increasing NPP sustained a continuing increase in terrestrial carbon storage through the Holocene. These results do not support the published hypothesis that terrestrial CO2 outgassing drove the ca. 20 ppm increase in [CO2]atm after 8 ka. They are consistent with an alternative explanation based on the oceanic CaCO3 compensation response to the extraction of carbon from the atmosphere-ocean system during the deglaciation.