HR: 08:00h
AN: PP21D-01    [Abstracts]
TI: Inverse process modelling to reconstruct past vegetation and climate
AU: * Guiot, J
EM: guiot@cerege.fr
AF: CEREGE - CNRS, BP 80 Europole de l'Arbois, Aix-en-Provence, 13545 France
AU: Wu, H
EM: haibin_wu2001@yahoo.com
AF: CEREGE - CNRS, BP 80 Europole de l'Arbois, Aix-en-Provence, 13545 France
AB: Vegetations models simulate vegetation characteristic variations in response to climate, CO2 and soil texture changes. Paleodata, in particular pollen data, provide information on past vegetation structure and composition. The model outputs can then be compared to these paleodata and by inversion, it is possible to retrieve the most probable vegetation compatible with these data. Massive computation algorithms (MCMC) are used to facilate that inversion. We present an application using pollen data for the Last Glacial Maximum (LGM: 21 ka BP) and model BIOME4. Land surface maps show a strong recession of the forest during the LGM. Temperature and precipitation maps show a colder and dryer climate especially in Europe. These results are coherent with previous results obtained with statistical approaches. Sensitivity tests show that CO2 does not induced an important bias when a calibration is done on modern data under an much richer CO2 environment. Nevertheless, if precipitation is the major factor to explain the tree-line decrease during the LGM, our approach proves that CO2 is also significant factor. This model-based approach does not replace statistical approaches as model itself does not represent perfectly the reality, but it is necessary to understand the interactions between past vegetation and climate and to check if other factors can induce biases in the reconstruction. Moreover, as such vegetation models simulate also water budget, dC13, it can be used to integrate the different proxies measured on a given core (diatoms, isotopes ...)
DE: 0428 Carbon cycling (4806)
DE: 1630 Impacts of global change (1225)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4914 Continental climate records
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005