HR: 15:05h
AN: U13A-05    [Abstracts]
TI: Understanding Chad Basin Evolution Since Miocene: Climate and Vegetation Simulations, Roles of Orbital Parameters and East African Rift.
AU: * Sepulchre, P
EM: psepul@cea.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS, L'Orme des Merisiers, batiment 709, Gif sur Yvette, 91191 France
AU: Ramstein, G
EM: Gilles.Ramstein@cea.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS, L'Orme des Merisiers, batiment 709, Gif sur Yvette, 91191 France
AU: Krinner, G
EM: krinner@ujf-grenoble.fr
AF: LGGE / CNRS, 54 Rue Moliere, BP 96, Saint Martin d'HŠres, 38402 France
AU: Schuster, M
EM: mathieu.schuster@uni-koeln.de
AF: Cologne University - Heinrich Barth Institute, Jennerstrasse 8., COLOGNE, 50823 Germany
AU: Fluteau, F
EM: fluteau@ipgp.jussieu.fr
AF: IPG Paris, 4, place jussieu, Paris, 75252 France
AU: Kageyama, M
EM: masa@lsce.saclay.cea.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS, L'Orme des Merisiers, batiment 709, Gif sur Yvette, 91191 France
AU: Tiercelin, J
EM: tiercelin@univ-brest.fr
AF: Institut Universitaire Europeen de la Mer. UMR 6538 "Domaines Oc‚aniques", Place N. Copernic, Plouzan‚, 29280 France
AU: Vignaud, P
EM: Patrick.Vignaud@univ-poitiers..fr
AF: Laboratoire de Geobiologie, Biochronologie et Paleontologie Humaine UFR - SFA Universit‚ de Poitiers, 40, avenue du Recteur Pineau, Poitiers, 86022 France
AU: Brunet, M
EM: Michel.Brunet@univ-poitiers.fr
AF: Laboratoire de Geobiologie, Biochronologie et Paleontologie Humaine UFR - SFA Universit‚ de Poitiers, 40, avenue du Recteur Pineau, Poitiers, 86022 France
AB: Since the discovery of the earliest hominid known, Chad basin is a major place to study paleoclimates and hominid evolution. This discovery implies to re-evaluate the "East Side Story" paradigm for early hominids. To achieve this goal, we have performed numerical simulations to quantify the climatic and vegetation response of the Rift Uplift. We used a zoomed (144 X 108) AGCM (LMDz from IPSL). On the one hand, offline continental biosphere model (ORCHIDEE) has been used to simulate the vegetation response over western and eastern parts of the rift. On the other hand, since geomorphologic evidences have shown that from Upper Miocene to mid-Holocene Lake Chad had known several level oscillations leading to a huge lake known as Mega Lake Chad (MLC), we also ran atmospheric simulations to demonstrate, with boundary conditions at 6 000 BP, that orbital forcing allowed the existence of a MLC. Volume and surface of the lake have been calculated using an adapted lake model. These simulations have shown that the ITCZ shift induced by the mid-Holocene orbital parameters drives the existence of a MegaChad. Our model result having been tested successfully for the last occurrence of the MLC, we will apply it to Upper Miocene accounting for topographic changes, in order to reconstruct as accurately as possible the first hominids environments.
DE: 9305 Africa
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
SC: Union [U]
MN: 2004 AGU Fall Meeting