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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 27 Mar 2020

Submitted as: research article | 27 Mar 2020

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This preprint is currently under review for the journal CP.

Simulating Marine Isotope Stage 7 with a coupled climate-ice sheet model

Dipayan Choudhury1,2, Axel Timmermann1,2, Fabian Schloesser3, Malte Heinemann4, and David Pollard5 Dipayan Choudhury et al.
  • 1Center for Climate Physics, Institute for Basic Science (IBS), Busan 46241, South Korea
  • 2Pusan National University, Busan 46241, South Korea
  • 3International Pacific Research Center, University of Hawaii at Manoa, Honolulu, HI 96822, USA
  • 4Institute of Geosciences, Kiel University, 24118, Kiel, Germany
  • 5Earth and Environmental Systems Institute, Pennsylvania State University, Pennsylvania 16802, USA

Abstract. It is widely accepted that orbital variations are responsible for the generation of glacial cycles during the late Pleistocene. However, the relative contributions of the orbital forcing compared to CO2 variations and other feedback mechanisms causing the waxing and waning of ice-sheets have not been fully understood. Testing theories of ice-ages beyond statistical inferences, requires numerical modeling experiments that capture key features of glacial transitions. Here, we focus on the glacial build-up from Marine Isotope Stage (MIS) 7 to 6 covering the period from 240–170 ka (thousand years before present). This transition from interglacial to glacial conditions includes one of the fastest Pleistocene glaciation/deglaciation events which occurred during MIS 7e-7d-7c (236–218 ka). Using a newly developed three-dimensional coupled atmosphere-ocean-vegetation-ice-sheet model (LOVECLIP), we simulate the transient evolution of northern and southern hemisphere ice-sheets during the MIS 7-6 period in response to orbital and greenhouse-gas forcing. For a range of model parameters, the simulations capture the reconstructed evolution of global ice volume reasonably well. It is demonstrated that glacial inceptions are more sensitive to orbital variations, whereas terminations from deep glacial conditions need both orbital and greenhouse gas forcings to work in unison. For some parameter values, the coupled model also exhibits a critical North American ice sheet configuration, beyond which a stationary wave – ice-sheet topography feedback can trigger an unabated and unrealistic ice-sheet growth. The strong parameter sensitivity found in this study originates from the fact that delicate mass imbalances, as well as errors, are integrated during a transient simulation for thousands of years. This poses a general challenge for transient coupled climate-ice sheet modeling.

Dipayan Choudhury et al.

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Dipayan Choudhury et al.

Dipayan Choudhury et al.


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Latest update: 02 Jun 2020
Publications Copernicus
Short summary
Our study is the first study to conduct transient simulations over MIS 7, using a 3-D coupled climate – ice sheet model with interactive ice sheets in both hemispheres. We find glacial inceptions to be more sensitive to orbital variations, whereas glacial terminations need the concerted action of both orbital and CO2 forcings. We highlight the issue of multiple equilibria and an instability due to stationary wave – topography feedback that can trigger unrealistic North American ice sheet growth.
Our study is the first study to conduct transient simulations over MIS 7, using a 3-D coupled...