HR: 0800h
AN: PP11A-1440    [Abstracts]
TI: Shift in Original Isotopic Signature of Plants due to Degradation and Paleoclimatic Implications: Contribution of the Modeling
AU: * Hatte, C
EM: hatte@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, UMR 1572 CEA-CNRS, Batt 12, Domaine du CNRS, Avenue de la Terrasse, Gif-sur-Yvette, 91198 France
AU: * Hatte, C
EM: hatte@lsce.cnrs-gif.fr
AF: NSF Arizona AMS Laboratory, Physics building, PO Box 210081, Tucson, AZ 85721-0081 United States
AU: Rousseau, D
EM: denis@dstu.univ-montp2.fr
AF: Institut des Sciences de l'Evolution, UMR CNRS-UM2 5554, Universite Montpellier II case 61, place E. Bataillon, Montpellier, 34095 France
AU: Rousseau, D
EM: denis@dstu.univ-montp2.fr
AF: Lamont-Doherty Earth Observatory, Columbia University, palissades, NY 10964 United States
AU: Rousseau, D
EM: denis@dstu.univ-montp2.fr
AF: Lehrstuhl fuer Geomorphologie, Universitaet Bayreuth, Bayreuth, 95447 Germany
AU: Guiot, J
EM: guiot@cerege.fr
AF: CEREGE, UMR CNRS - Universite P. Cezanne 6635, BP 80, Aix-en-Provence, 13545 France
AU: Kukla, G
EM: kukla@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, palissades, NY 10964 United States
AB: Isotopic studies performed on bulk organic matter or on specific biomarkers have been widely used to reconstruct climates of the past. However, they are based on the assumption that the measured isotopic composition perfectly reflects the original isotopic composition. But few natural environments agree with. Usually, microbial degradation induces a distortion of the original δ¹³C that is poorly known: ranging from a 1‰ enrichment to a 2‰ depletion according to the environments. We present here the benefit in applying the inverse modeling of a terrestrial vegetation model on δ¹³C measurements to evaluate the most probable degradation shift. This study, applied on the Grande Pile peat record, thrusts forward that microbial degradation induces a depletion of the bulk isotopic composition of the vegetation. This depletion is likely to be of 1‰ in magnitude. The second result addresses paleoclimatology reconstructions by specifying the added value of the isotopic composition associated to the palynological spectra as a forcing parameter for inverse modeling. Indeed, this study highlights variation ranges of annual precipitation and/or temperature narrower using an inverse modeling procedure with δ¹³C than without. These narrow ranges allow to reveal expected climatic trends that were noticed in marine sediments and on continent but not precisely reconstructed.
DE: 0429 Climate dynamics (1620)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1055 Organic and biogenic geochemistry
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 3354 Precipitation (1854)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005