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

这项提议的总体目标是重建过去100 Ma的特定时间间隔内的温度和冰量变化及其对海洋环流和海洋生态系统的影响，这对我们理解地球的古气候动力学特别关键。为了解决有争议的古气候和古海洋学问题，拟议的项目将采用新的碳酸盐“块状同位素”古温度计(CCIP)，这是一种基于海底有孔虫孔隙特征(BFPC)和有孔虫组合数据的新的古氧代用品。总体项目目标将通过三个阶段的方法实现，其中包括(I)测试CCIP和BFPC，(Ii)校准选定有孔虫分类群的两个替代物，以及(Iii)将其用于研究中新生代和中生代选定的时间片。阶段(三)将包括7个案例研究，在这些案例研究中，将结合“经典”替代指标(例如，δ18O、镁/钙和集合体计数)进行CCIP和BFPC分析。这一综合方法将能够将温度信号与冰/盐度信号分开，并破译对海洋环流和生态系统的各自影响，这将对有争议的古气候和古海洋过程产生新的见解。这项拟议的研究最终可以向解决白垩纪温室到今天的冰库世界的冰温难题迈出重要的一步。

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.