Ocean circulation and carbon cycling during Eocene 'greenhouse' warmth

海洋环流通过向极地输送热量和盐分强烈地影响气候。更新世深海沉积物记录表明，海洋环流可以通过控制海洋翻转的半球开关（千年尺度Dansgaard-Oeschger气候周期的“两极跷跷板”）以及通过其在二氧化碳储存和释放中的作用（例如跨越冰川-间冰期周期）来驱动全球气候。然而，海洋环流对大气中二氧化碳水平的根本不同有多敏感，这一点还不得而知。预计人为的二氧化碳排放将使这种温室气体在大气中的浓度升高，到本世纪末，其浓度将高于始新世以来的任何时候。然而，实际上没有合适的数据从始新世与测试的性质和稳定性的海洋环流在这种“温室”气候制度的特点是高CO2水平，最小的大陆冰量和对比模式的碳cycleization.This工作的目的是重建全球配置和相对强度的海洋环流的早期和中期始新世的关键间隔。我将使用综合大洋钻探计划从纽芬兰边缘以及全球一系列地点恢复的深海沉积物序列。对底栖有孔虫方解石的稳定氧和碳同位素分析将提供全球沉积物序列之间的强有力的相关性，并为重建海洋环流模式提供替代。对南极有孔虫成岩涂层和鱼牙氟磷灰石的新同位素分析将为重建海洋环流的变化提供独立的工具。

Ocean circulation strongly influences climate by poleward transport of heat and salt. The Pleistocene deep-sea sediment record shows that ocean circulation can drive global climate via switches in the hemisphere dominating ocean overturning (the 'bipolar seesaw' of millennial-scale Dansgaard-Oeschger climate cycles) and via its role in storage and release of carbon dioxide (e.g. across glacial-interglacial cycles). However, what is not known is how sensitive ocean circulation is to radically different levels of atmospheric carbon dioxide. Man-made CO2 emissions are projected to elevate atmospheric concentrations of this greenhouse gas to levels that, by the end of this century, will be higher than at any time since the Eocene epoch. Yet there are virtually no appropriate data from the Eocene with which to test the nature and stability of ocean circulation during such 'greenhouse' climate regimes characterized by high CO2 levels, minimal continental ice volume and contrasting modes of carbon cycling.This work aims to reconstruct the global configuration and relative strength of ocean circulation through key intervals of the early and middle Eocene. I will use deep sea sediment sequences recovered by the Integrated Ocean Drilling Program from the Newfoundland margin, in addition to a series of locations worldwide. Stable oxygen and carbon isotope analyses of benthic foraminiferal calcite will provide robust correlations between sediment sequences worldwide and a proxy for reconstructing ocean circulation patterns. Neodymium isotope analyses of planktic foraminiferal diagenetic coatings and of the fluorapatite of fish teeth will provide independent tools for reconstructing changes in ocean circulation.