Ocean circulation and the ice-temperature conundrum: Unraveling the transition from the Cretaceous greenhouse into today's icehouse world

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The overall goal of this proposal is to reconstruct temperature and ice-volume changes and their effects on ocean circulation and marine ecosystems for specific time intervals of the past 100 Ma that are particularly critical for our understanding of the Earth’s paleoclimatic dynamics. To tackle controversially discussed paleoclimatic and paleoceanographic issues, the proposed project will employ the novel carbonate “clumped-isotope” paleothermometer (CCIP), a new paleo-oxygenation proxy based on benthic foraminiferal pore characteristics (BFPC), and foraminiferal assemblage data. The overall project goals will be achieved following a threestage approach that comprises (I) testing of CCIP and BFPC, (II) the calibration of both proxies for selected foraminiferal taxa, and (III) their employment in studies on selected time slices of the Ceno- and Mesozoic. Stage (III) will comprise seven case studies where CCIP and BFPC analyses will be combined with “classical” proxies (e.g., δ18O, Mg/Ca, and assemblage counts). This integrated approach will allow to separate temperature from ice/salinity signals and to decipher the respective effects on ocean circulation and ecosystems, which will yield new insights into controversially discussed paleoclimatic and paleoceanographic processes. The proposed research can ultimately provide a significant step forward towards resolving the icetemperature conundrum for the Cretaceous greenhouse to the present-day’s icehouse world.