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www.clim-past-discuss.net/7/1935/2011/
doi:10.5194/cpd-7-1935-2011
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The Middle Miocene climate as modelled in an atmosphere-ocean-biosphere model
1Max-Planck Institut für Meteorologie, Hamburg, Germany
2International Max Planck Research School on Earth System Modelling, Hamburg, Germany
Abstract. We present simulations with a coupled ocean-atmosphere-biosphere model for the Middle Miocene 15 million years ago. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulations, causes a global warming of 0.7 K compared to present-day. Higher than present-day CO2 levels of 480 and 720 ppm cause a global warming of 2.8 and 4.9 K, thereby matching proxy-based Middle Miocene global temperature estimates of 3–6 K warming. Higher CO2 levels and the associated water vapour feedback enhance the greenhouse effect and lead to a polar amplification of the warming. Although oceanic and atmospheric poleward heat transport are individually altered by 10–30 % in the mid and high latitudes, changes of the total heat transport account only for 4–8 %, pointing toward a compensation between oceanic and atmospheric heat transport. Our model reproduces a denser vegetation in agreement with fossil records. These results suggest that higher than present-day CO2 levels are essential to drive the warm Middle Miocene climate.
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Notice on Discussion StatusCitation: Krapp, M. and Jungclaus, J. H.: The Middle Miocene climate as modelled in an atmosphere-ocean-biosphere model, Clim. Past Discuss., 7, 1935-1972, doi:10.5194/cpd-7-1935-2011, 2011. Bibtex EndNote Reference Manager XML
