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Climate of the Past An interactive open-access journal of the European Geosciences Union

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Clim. Past Discuss., 9, 297-328, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research Article
18 Jan 2013
Review Status
This discussion paper has been under review for the journal Climate of the Past (CP). A final paper in CP is not foreseen.
A Last Glacial Maximum world-ocean simulation at eddy-permitting resolution – Part 1: Experimental design and basic evaluation
M. Ballarotta1, L. Brodeau1, J. Brandefelt2, P. Lundberg1, and K. Döös1
1Department of Meteorology/Oceanography, Stockholm University, 106 91 Stockholm, Sweden
2Department of Mechanics, KTH (Royal Institute of Technology), 106 91 Stockholm, Sweden

Abstract. Most state-of-the-art climate models include a coarsely resolved oceanic component, which has difficulties in capturing detailed dynamics, and therefore eddy-permitting/eddy-resolving simulations have been developed to reproduce the observed World Ocean. In this study, an eddy-permitting numerical experiment is conducted to simulate the global ocean state for a period of the Last Glacial Maximum (LGM, ~ 26 500 to 19 000 yr ago) and to investigate the improvements due to taking into account these higher spatial scales. The ocean general circulation model is forced by a 49-yr sample of LGM atmospheric fields constructed from a quasi-equilibrated climate-model simulation. The initial state and the bottom boundary condition conform to the Paleoclimate Modelling Intercomparison Project (PMIP) recommendations. Before evaluating the model efficiency in representing the paleo-proxy reconstruction of the surface state, the LGM experiment is in this first part of the investigation, compared with a present-day eddy-permitting hindcast simulation as well as with the available PMIP results. It is shown that the LGM eddy-permitting simulation is consistent with the quasi-equilibrated climate-model simulation, but large discrepancies are found with the PMIP model analyses, probably due to the different equilibration states. The strongest meridional gradients of the sea-surface temperature are located near 40° N and S, this due to particularly large North-Atlantic and Southern-Ocean sea-ice covers. These also modify the locations of the convection sites (where deep-water forms) and most of the LGM Conveyor Belt circulation consequently takes place in a thinner layer than today. Despite some discrepancies with other LGM simulations, a glacial state is captured and the eddy-permitting simulation undertaken here yielded a useful set of data for comparisons with paleo-proxy reconstructions.

Citation: Ballarotta, M., Brodeau, L., Brandefelt, J., Lundberg, P., and Döös, K.: A Last Glacial Maximum world-ocean simulation at eddy-permitting resolution – Part 1: Experimental design and basic evaluation, Clim. Past Discuss., 9, 297-328, doi:10.5194/cpd-9-297-2013, 2013.
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