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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/gmd-2019-332
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gmd-2019-332
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: model description paper 09 Dec 2019

Submitted as: model description paper | 09 Dec 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).

IPSL-CM5A2. An Earth System Model designed for multi-millennial climate simulations

Pierre Sepulchre1, Arnaud Caubel1, Jean-Baptiste Ladant1,2, Laurent Bopp3, Olivier Boucher4, Pascale Braconnot1, Patrick Brockmann1, Anne Cozic1, Yannick Donnadieu5, Victor Estella-Perez6, Christian Ethé8, Frédéric Fluteau7, Marie-Alice Foujols8, Guillaume Gastineau6, Josefine Ghattas8, Didier Hauglustaine1, Frédéric Hourdin4, Masa Kageyama1, Myriam Khodri6, Olivier Marti1, Yann Meurdesoif1, Juliette Mignot6, Anta-Clarisse Sarr5, Jérôme Servonnat1, Didier Swingedouw9, Sophie Szopa1, and Delphine Tardif7 Pierre Sepulchre et al.
  • 1Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 2Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor MI 48109, USA
  • 3Laboratoire de Météorologie Dynamique, Sorbonne Université/CNRS/École Normale Supérieure, Paris, France
  • 4Laboratoire de Météorologie Dynamique, IPSL, CNRS, Sorbonne Université, Paris, France
  • 5CEREGE, Aix-Marseille University, CNRS, IRD, Coll. France, INRA, Technopole Arbois-Méditerranée, BP80, 13545 Aixen Provence cedex 4, France
  • 6Laboratoire d’Océanographie et du Climat : Expérimentations et Approches Numériques, Sorbonne Université/CNRS, 4place Jussieu, 75252 Paris Cedex 05, France
  • 7Université de Paris, Institut de physique du globe de Paris, CNRS, 75005 Paris, France
  • 8Institut Pierre-Simon-Laplace, Sorbonne Université/CNRS, Paris, France
  • 9Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR CNRS 5805, EPOC, OASU, Universitéde Bordeaux, Allée Geoffroy Saint-Hilaire, Pessac 33615, France

Abstract. Based on the CMIP5-generation previous IPSL earth system model, we designed a new version, IPSL-CM5A2, aiming at running multi-millennial simulations typical of deep-time paleoclimates studies. Three priorities were followed during the set-up of the model: (1) improving the overall model computing performance, (2) overcoming a persistent cold bias depicted in the previous model generation, and (3) making the model able to handle the specific continental configurations of the geological past. Technical developments have been performed on separate components and on the coupling system to speed up the whole coupled model. These developments include the integration of hybrid parallelization MPI-OpenMP in LMDz atmospheric component, the use of a new library to perform parallel asynchronous input/output by using computing cores as “IO servers”, the use of a parallel coupling library between the ocean and the atmospheric components. The model can now simulate ~100 years per day, opening new possibilities towards the production of multi-millennial simulations with a full earth system model. The tuning strategy employed to overcome a persistent cold bias is detailed. The confrontation of an historical simulation to climatological observations shows overall improved ocean meridional overturning circulation, marine productivity and latitudinal position of zonal wind patterns. We also present the numerous steps required to run the IPSL-CM5A2 for deep-time paleoclimates through a preliminary case-study for the Cretaceous. Namely, a specific work on the ocean model grid was required to run the model for specific continental configurations in which continents are relocated according to past paleogeographic reconstructions. By briefly discussing the spin-up of such a simulation, we elaborate on the requirements and challenges awaiting paleoclimate modelling in the next years, namely finding the best trade-off between the level of description of the processes and the computing cost on supercomputers.

Pierre Sepulchre et al.
Interactive discussion
Status: open (until 13 Feb 2020)
Status: open (until 13 Feb 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Pierre Sepulchre et al.
Data sets

IPSL-CM5A2. An Earth System Model designed for multi-millennial climate simulations: Boundary conditions and outputs. Pierre Sepulchre; Arnaud Caubel; Jean-Baptiste Ladant; Laurent Bopp; Olivier Boucher; Pascale Braconnot; Patrick Brockmann; Anne Cozic; Yannick Donnadieu; Victor Estella-Perez; Christian Ethé; Frédéric Fluteau; Marie-Alice Foujols; Guillaume Gastineau; Josefine Ghattas; Didier Hauglustaine; Frédéric Hourdin; Masa Kageyama; Myriam Khodri; Olivier Marti; Yann Meurdesoif; Juliette Mignot; Anta-Clarisse Sarr; Jérôme Servonnat; Didier Swingedouw; Sophie Szopa; Delphine Tardif https://doi.org/10.5281/zenodo.3549769

Model code and software

IPSL-CM5A2-diags: Jupyter notebook first release Pierre Sepulchre; Patrick Brockmann https://doi.org/10.5281/zenodo.3549652

Pierre Sepulchre et al.
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Short summary
Our paper describes IPSL-CM5A2, an earth system model that can be integrated for long (several thousands of years) climate simulations. We describe the technical aspects, assess the model computing performances and evaluate the strengths and weaknesses of the model, by comparing pre-industrial and historical runs to the previous generation model simulations and to observations. We also present a Cretaceous simulation as a case-study to show how the model simulate deep time paleoclimates.
Our paper describes IPSL-CM5A2, an earth system model that can be integrated for long (several...
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