Stripping back the modern to reveal the Cenomanian-Turonian climate and temperature gradient underneath

• Published in: Climate of the Past
• Main Authors: Laugié, Marie, Donnadieu, Yannick, Ladant, Jean-Baptiste, Green, J., Bopp, Laurent, Raisson, François
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), NASA Headquarters, Bangor University, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre scientifique et Technique Jean Feger (CSTJF), TOTAL FINA ELF
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Laplace; Ice Sheet
• Online Access: https://hal.sorbonne-universite.fr/hal-02877750; https://hal.sorbonne-universite.fr/hal-02877750/document; https://hal.sorbonne-universite.fr/hal-02877750/file/cp-16-953-2020.pdf; https://doi.org/10.5194/cp-16-953-2020

International audience During past geological times, the Earth experienced several intervals of global warmth, but their driving factors remain equivocal. A careful appraisal of the main processes controlling past warm events is essential to inform future climates and ultimately provide decision makers with a clear understanding of the processes at play in a warmer world. In this context, intervals of greenhouse climates , such as the thermal maximum of the Cenomanian-Turonian (∼ 94 Ma) during the Cretaceous Period, are of particular interest. Here we use the IPSL-CM5A2 (IPSL: In-stitut Pierre et Simon Laplace) Earth system model to unravel the forcing parameters of the Cenomanian-Turonian greenhouse climate. We perform six simulations with an in-cremental change in five major boundary conditions in order to isolate their respective role on climate change between the Cenomanian-Turonian and the preindustrial. Starting with a preindustrial simulation, we implement the following changes in boundary conditions: (1) the absence of polar ice sheets, (2) the increase in atmospheric pCO 2 to 1120 ppm, (3) the change in vegetation and soil parameters, (4) the 1 % decrease in the Cenomanian-Turonian value of the solar constant and (5) the Cenomanian-Turonian palaeo-geography. Between the preindustrial simulation and the Cre-taceous simulation, the model simulates a global warming of more than 11 • C. Most of this warming is driven by the increase in atmospheric pCO 2 to 1120 ppm. Palaeogeo-graphic changes represent the second major contributor to global warming, whereas the reduction in the solar constant counteracts most of geographically driven warming. We further demonstrate that the implementation of Cenomanian-Turonian boundary conditions flattens meridional temperature gradients compared to the preindustrial simulation. Interestingly , we show that palaeogeography is the major driver of the flattening in the low latitudes to midlatitudes, whereas pCO 2 rise and polar ice sheet retreat dominate the high-latitude ...