Influence of dynamic vegetation on climate change and terrestrial carbon storage in the Last Glacial Maximum
1Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Japan
2National Institute of Polar Research, Tokyo, Japan
3Frontier Research Center for Global Change, Yokohama, Japan
Abstract. When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago) is cold and dry compared to the present day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 level (185 ppm compared to a preindustrial level of 285 ppm). In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (GCM, the MIROC-LPJ). We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback) and quantified the strength of the vegetation feedback during the LGM. The result shows global-averaged cooling during the LGM is amplified by +13.5% due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using a separated Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM). Our result shows that the total terrestrial carbon storage was reduced by 653 PgC during the LGM, which corresponds to the emission of 308 ppm atmospheric CO2. The carbon distribution during the LGM that is predicted from using an atmospheric-ocean-vegetation (AOV) GCM and using the LPJ-DGVM after an atmospheric-ocean (AO) GCM, is generally the same, but the difference is not negligible for explaining the lowering of atmospheric CO2 during the LGM.