Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 5 1 2009 10.5194/cpd-5-251-2009 http://www.clim-past-discuss.net/5/251/2009/ http://www.clim-past-discuss.net/5/251/2009/cpd-5-251-2009.html http://www.clim-past-discuss.net/5/251/2009/cpd-5-251-2009.pdf 251 285 2009-01-26 Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates* M. Sarnthein ms@gpi.uni-kiel.de M. Prange A. Schmittner B. Schneider M. Weinelt Institute for Geosciences, University of Kiel, 24098 Kiel, Germany Institute for Geology and Paleontology, University of Innsbruck, 6020, Austria MARUM Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, 28334 Bremen, Germany College of Ocean and Atmospheric Sciences, Oregon State University, Corvallis OR 97331-5503, USA * Invited contribution by M. Sarnthein, EGU Milutin Milankovic Medal winner 2006 A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern Hemisphere Glaciation (NHG) and pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic, that and continue until today. The severe deterioration of climate occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma (glacial MIS G6/4). Various models and paleoceanographic records (intercalibrated using orbital age control) suggest clear linkages between the onset of NHG and three steps in the final closure of the Central American Seaways (CAS), deduced from rising salinity differences between Caribbean and East Pacific. Each closing event led to enhanced North Atlantic meridional overturning circulation and strengthened the poleward transport of salt and heat (warmings of +2–3°C). 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