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Do tropical conditions determine climate sensitivity? Lessons from the warm PlioceneChristina RaveloAssociate Professor of Ocean Sciences The last 5 Ma of Earth's history includes a shift from global warmth of the early Pliocene to globally cold conditions of the Pleistocene, and therefore provides an opportunity to understand the causes of major climate transitions. It also provides an opportunity to compare how climate behavior such as its sensitivity to solar forcing is different in a exist, the lack of records from tropical and subtropical regions has prevented scientists from testing theories about the causes of the warm to cold transition and of the changes in climate sensitivity. Using tropical and subtropical records from the Pacific we document that major reorganization of low latitude conditions, specifically the development of Walker circulation in the tropical Pacific and cooling of upwelling regions in the subtropics, occurred just after 2.0 Ma. This is well after major tectonic events in the tropical regions and after the onset of significant Northern Hemisphere Glaciation, indicating that glaciation was not driven by tropical processes. However, an analysis of how ice sheet respond to solar forcing demonstrates that the sensitivity of the response is greatest just after about 2.0 Ma. This indicates that mean tropical conditions potentially have a large influence on the sensitivity of global climate to perturbations. About the LecturerAreas of interestpaleoceanography, paleoclimatology, stable isotope geochemistry Education
1991 Columbia University, NY, NY Ph. D. in Geological Sciences Current ProjectsMy students and I are currently working on generating records of the evolution of the tropical oceans and of the California and Peru-Chile margins through the Pliocene to try to understand the causes of the transition from the warm early Pliocene to the cold Pleistocene and how perturbations such as solar forcing are amplified. We are working on details of tropical paleoclimatology during the last glacial cycle, with the goal of understanding the applicability of modern day analogs, such as El Niño, to understanding climate change that occurred on geological timescales. Another project is focused on understanding the generation of sub-Milankovitch climate cycles in the Atlantic using statistical techniques for understanding the non-linear couplings between records and between different frequencies of change. In addition, we have collaborative projects with other labs focusing on high accumulation rate sediments from Palmer Deep, submerged ancient corals from Papua New Guiniea, modern corals from the Northwest Hawaiian Islands, and the calibration of paleoproxies such as calcium isotopes and Mg/Ca. More Information |
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