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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 17 Jul 2019

Submitted as: research article | 17 Jul 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Climate of the Past (CP).

Modelling a Modern-like-pCO2 Warm Period (MIS KM5c) with Two Versions of IPSL AOGCM

Ning Tan1,2, Camille Contoux2, Gilles Ramstein2, Yong Sun3, Christophe Dumas2, and Pierre Sepulchre2 Ning Tan et al.
  • 1Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
  • 2Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
  • 3State Key Laboratory of Numerical Modellingfor Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

Abstract. The mid-Piacenzian warm period (3.264 to 3.025 Ma) is the most recent geological period with a present-like atmospheric pCO2 exhibiting significant warming relative to present conditions. With the advanced understanding of the climate variability of this interval, a specific interglacial (marine isotope stage KM5c, MIS KM5c, 3.205 Ma) is selected for Pliocene Model Intercomparison Project phase 2 (PlioMIP 2) and updated boundary conditions are provided. In this study, we carried out series of experiments according to the design of PlioMIP2 with two versions of the IPSL Atmosphere-Ocean Coupled General Circulation Model (AOGCM) (IPSL-CM5A and IPSL-CM5A2). By comparing with PlioMIP 1 experiment, run with IPSL-CM5A, our results show that the simulated MIS KM5c climate presents enhanced warming in mid-to-high latitudes, especially in ocean regions. This warming can be attributed to the largely enhanced Atlantic Meridional Overturning Circulation caused by the high latitude seaway changes. The tier experiments, conducted with IPSL-CM5A2 (with faster computation scheme), show that besides the increased pCO2, both modified orography and reduced ice sheets contribute substantially in mid-to-high latitudes warming of MIS KM5c. When considering the pCO2 uncertainties, the warming pattern changes, our model response to the variation of pCO2 by ±50 ppmv is not symmetric in the surface air temperature, due to the non-linear response of the cryosphere (snow cover and sea ice extent). By analysing the Greenland Ice Sheet surface mass balance, we also demonstrate its vulnerability under both MIS KM5c and modern warm climate.

Ning Tan et al.
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Ning Tan et al.
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Publications Copernicus
Short summary
To understand the warm climate occurred during the late Pliocene (~ 3.205 Ma), several simulations with the PlioMIP2 boundary conditions based on the IPSL AOGCM are launched and analysed. It is found that the warming in mid-to-high latitudes enhanced due to the modifications of land sea mask and land ice configuration. The pCO2 uncertainties within the records can affect this warm pattern asymmetrically. Moreover, the margin of Greenland ice sheet become more vulnerable under this warm climate.
To understand the warm climate occurred during the late Pliocene (~ 3.205 Ma), several...