Influence of dynamic vegetation on climate change and terrestrial carbon storage in the Last Glacial Maximum

摘要

When the climate is reconstructed from paleoevidence, itshows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago) is cold anddry compared to the present-day. Reconstruction also shows that compared totoday, the vegetation of the LGM is less active and the distribution ofvegetation was drastically different, due to cold temperature, dryness, and alower level of atmospheric CO₂ concentration (185 ppm compared to apreindustrial level of 285 ppm). In the present paper, we investigate theinfluence of vegetation change on the climate of the LGM by using a coupledatmosphere-ocean-vegetation general circulation model (AOVGCM, theMIROC-LPJ). The MIROC-LPJ is different from earlier studies in theintroduction of a bias correction method in individual running GCMexperiments. We examined four GCM experiments (LGM and preindustrial, withand without vegetation feedback) and quantified the strength of thevegetation feedback during the LGM. The result shows that global-averagedcooling during the LGM is amplified by +13.5 % due to the introduction ofvegetation feedback. This is mainly caused by the increase of land surfacealbedo due to the expansion of tundra in northern high latitudes and thedesertification in northern middle latitudes around 30° N to60° N. We also investigated how this change in climate affected thetotal terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamicglobal vegetation model (LPJ-DGVM). Our result shows that the totalterrestrial carbon storage was reduced by 597 PgC during the LGM, whichcorresponds to the emission of 282 ppm atmospheric CO₂. In the LGMexperiments, the global carbon distribution is generally the same whether thevegetation feedback to the atmosphere is included or not. However, theinclusion of vegetation feedback causes substantial terrestrial carbonstorage change, especially in explaining the lowering of atmospheric CO₂during the LGM.