Climate and low latitude water cycle variations during the Quaternary : a model-data approach

• Main Author: Extier, Thomas
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Paris Saclay (COmUE), Amaëlle Landais, Didier Roche
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2019
• Subjects: Low latitude hydrological cycle; Isotopic composition of atmospheric oxygen; Ice core; Chronology; Climate modeling; Cycle hydrologique des basses latitudes; Composition isotopique de l'oxygène de l'air; Carotte de glace; Chronologie; Modélisation du climat; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; EPICA; ice core
• Online Access: https://theses.hal.science/tel-02986449; https://theses.hal.science/tel-02986449/document; https://theses.hal.science/tel-02986449/file/79543_EXTIER_2019_archivage.pdf

Quaternary glacial-interglacial cycles are recorded in various climatic archives from high to low latitudes. The EPICA Dome C ice core provides a high-resolution record over the last 800 ka of δ18Oatm (i.e. δ18O of atmospheric O2) which combines past variations of the low latitude water cycle and of the biosphere productivity. In absence of annual layer counting, this proxy can be used for orbital dating in association with the June 21st insolation at 65°N to build an ice core chronology. However a lag of 6 ka between the δ18Oatm and the insolation, classically observed during glacial-interglacial terminations, is applied to the entire record during the chronology construction. This lag and the complexity of the δ18Oatm signal are the main reasons why the ice core chronology presents a high 6 ka uncertainty which limits their interpretation, jointly with other paleoclimate archives, in terms of past climate and environmental variations. To solve this issue I have developed a new ice core chronology based on the relation between the δ18Oatm and the δ18Ocalcite of east-asian speleothems, using new isotope measurements allowing for the first time a complete record over the last 800 ka at Dome C. This new chronology reduces the uncertainties compared to the actual ice core chronology strongly based on δ18Oatm and shows a better sequence of events between the high and low latitudes records. Then, I have developed a model to reproduce the isotopic composition of atmospheric O2 to address the lack of quantitative interpretations of this proxy and to check our assumption of synchronicity with the δ18Ocalcite over several climatic cycles. To reproduce the variations of the δ18Oatm, it was necessary to couple the intermediate complexity climate model iLOVECLIM and the vegetation model CARAIB. Finally, the δ18Oatm variations simulated with the new coupled model over several thousand years are in phase with the insolation of the Northern hemisphere (except during Heinrich events) and with low latitudes δ18Ocalcite ...