Universitaet Kiel, Federal Republic of Germany

The gradual shoaling of the Central American Seaway during the Pliocene altered the distribution of freshwater and heat in the global ocean. Surface- and deep-water circulation changed in the Atlantic, Pacific, and Arctic Oceans occurred as a consequence of the restriction of interbasin surface-water exchange by the tectonic closure of the Central American Seaway between about 4.6 and 2.7 million years ago. The altered oceanic circulation patterns increased thermohaline heat and moisture transports from low to high northern latitudes (Haug and Tiedemann 1998, Billups et al. 1999, Haug et al. 2001). The closure of the Central American Seaway initially pushed the climate system toward warmer conditions, the so-called Pliocene Warm Period between 4.6 and 3.1 million years ago (e.g., Budyko et al. 1985). However, the change in physical boundary conditions ultimately preconditioned the global climate system towards major ice sheet growth in the Northern Hemisphere, which started between 3.1 and 2.5 million years ago (e.g., Tiedemann et al. 1995).