| Summary: | Over the last 800 ky the Earth’s climate system has been triggered by orbitally- forced oscillations, referred to as glacial- interglacial cycles. However, the detailed dynamics of these cycles, specifically the transition between glacial into interglacial phase, are still to be completely understood. An interesting feature of these phases is that atmospheric CO2 and CH4 concentrations are better correlated with Antarctica and Greenland rather than with North Hemisphere temperatures, and this suggests the hypothesis that greenhouse gases are important amplifiers of the orbital forcing in the glacial-interglacial cycles. The cyclicity of biological marine productivity on glacial-interglacial scale observed both in the Pacific and further supports the idea that climate changes are cyclic and control the global carbon dynamics. Here, we investigate the role played by coccolithophores, a group of calcifying phytoplankton tightly connected to the global climate through the carbon cycle, during the last deglaciation in the Southern Ocean and Eastern Equatorial Pacific. The present thesis focuses on Termination I (TI), the latest warming event that the Earth has experienced, with the final aim to provide new insights on climate dynamics that are not still completely understood. In this PhD thesis, the response of calcareous phytoplankton to increased temperatures (global warming), shifts in the carbonate system (ocean acidification) and enhanced water column stratification (as a response to the increase in temperatures) have been analyzed. Our results are based on sediment samples recovered from two sites located in the South Atlantic area of the Southern Ocean (ODP1089 and PS2498-1; Chapters 2,3,4) and one in the Eastern Equatorial Pacific Ocean, off the coast of Ecuador (Site ODP1238; Chapter 5). These three case studies allowed an evaluation of the repeatability of our analyses (Chapter 2) and, more importantly, a better comprehension on several aspects related to coccolithophore community evolution and coccolith ...
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