HR: 08:15h
AN: PP21D-02    [Abstracts]
TI: Inverse modeling of biomes and delta_C to reconstruct the Grande Pile Eemian record: Characterization of an instable climate interval.
AU: * Rousseau, D
EM: denis@dstu.univ-montp2.fr
AF: Universite Montpellier II - CNRS, Institut Sciences Evolution, case 61, pl. E. Bataillon, Montpellier, 34095 France
AU: * Rousseau, D
EM: denis@dstu.univ-montp2.fr
AF: Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY 10964 United States
AU: Hatte, C
EM: hatte@lsce.cnrs-gif.fr
AF: LSCE, UMRS CEA_CNRS 1572, Domaine du CNRS, avenue de la terrasse, Gif-sur-Yvette, 91198 France
AU: Guiot, J
EM: guiot@cerege.fr
AF: Universite P Cezanne, CEREGE, Europole de l'Arbois, BP 80, Aix-en-Provence, 13545 France
AU: Duzer, D
EM: duzer@isem.univ-montp2.fr
AF: Universite Montpellier II - CNRS, Institut Sciences Evolution, case 61, pl. E. Bataillon, Montpellier, 34095 France
AU: Schevin, P
EM: schevin@isem.univ-montp2.fr
AF: Universite Montpellier II - CNRS, Institut Sciences Evolution, case 61, pl. E. Bataillon, Montpellier, 34095 France
AU: Kukla, G
EM: kukla@ldeo.columbia.edu
AF: Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY 10964 United States
AB: A new method to reconstruct past climatic conditions from pollen and isotopic data is applied to new counts from a new core, GP21, in the Grande Pile area. The climatic conditions reconstructed concerns the 130 to 100 kyr interval, which includes the Eemian lato sensu. To do so, we applied the Biome4 vegetation model in inverse mode to both pollen counts and δ¹³C values. The method considers the δ¹³C, measured in parallel to the pollen samples, as another constraint for the model. First the biomes and the δ¹³C simulated by the model are compared with the biome allocation, yielded after the biomisation of the pollen data, and the measured δ¹³C considered after a determined degradation effect on the preserved organic matter δ¹³C. This procedure allowed us the reconstruction of the mean annual temperature and precipitation and of the warmest and coldest months mean temperatures. We show that during the Eemian itself, the precipitation indicates similar values to the modern ones with no particular variation, contrary to the cold stadials and the penultimate glaciation characterized by very low values. Conversely the temperature estimates indicate different pattern. Indeed several oscillations are identified during the studied interval. The peak interglacial values are reached early at about 125-124 kyr, but two other warm intervals are identified afterwards. The variations of the temperature estimates seem related to sea surface oscillations occurring in the North Atlantic region and support the reconstruction of Northern Hemisphere ice-sheets building timing. Furthermore seasonality variations are also identified through the comparison of the warmest and coldest month temperatures, which indicate a different pattern during the studied interval.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1637 Regional climate change
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4914 Continental climate records
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005