HR: 11:05h
AN: PP32B-04    [Abstracts]
TI: Late Miocene Washhouse Climate due to Temporary Closure of Panama Seaway
AU: * Bohme, M
EM: m.boehme@lrz.uni-muenchen.de
AF: University Munich, Deptm. Geoscience, Section Paleontology, Richard-Wagner-Str. 10, Munich, 80333, Germany
AU: Ilg, A
EM: august.ilg@t-online.de
AF: University Munich, Deptm. Geoscience, Section Paleontology, Schumannstrasse 83, Duesseldorf, 40237, Germany
AU: Winklhofer, M
EM: m.winklhofer@gepphysik.uni-muenchen.de
AF: University Munich, Deptm. Geoscience, Section Geophysics, Theresienstrasse 41, Munich, 80333, Germany
AB: Tectonic processes have played an important role in driving long-term climatic change. It has been shown that the final closure of the Central American Seaway (CAS) in the Pliocene caused a major reorganization of ocean and atmospheric circulation. A comparable tectonic situation existed in the time interval between ~ 10.9 and 8.3 Ma, when the CAS was temporarily closed. To study the effects of such a major paleogeographic change on continental climate, we reconstructed an 8 million-year proxy record of European precipitation and runoff variations for the Middle to Late Miocene (5.3 to 13 Ma, temporal resolution ~ 60 kyr), based on the ecophysiological structure of herpetological (amphibians and reptiles) assemblages. Our data provide strong evidence of a washhouse climate in mid latitudes, characterized by a several-fold increase in the continental runoff induced by up to more than 200% increase in precipitation relative to recent. We interpret the washhouse climate in terms of a weakened Azores High due to a reversed oceanic northward heat transport upon closure of the CAS. The two intervals of washhouse climate (between 10.2-9.8 Ma and 9.0 -8.5 Ma) occur in warm periods, while the in-between interval (from 9.7 to 9.2 Ma) with a reduced hydrological cycle occurs in a globally cool period when the Atlantic Meridional Overturning Circulation (AMOC) was weaker. The transition between the washhouse and the cool climate may well have been fuelled by the enhanced atmospheric moisture transport into high latitudes and promoted by increasing amplitudes of obliquity variations. The reduced European hydrological cycle in the cool interval caused a severe biotic crisis, including the extinction of hominoids in Europe. Our data corroborate results from coupled ocean-atmosphere-land models predicting significant increases in the hydrological cycle in response to global warming.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1655 Water cycles (1836)
DE: 4914 Continental climate records
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting