Collaborative Research: Investigation of pCO2 Changes Since the Pliocene Based on Alkenone Carbon Isotopes

合作研究：基于烯烃碳同位素的上新世以来二氧化碳变化的研究Mark Pagani/A.Christina Ravelo耶鲁大学/加州大学圣克鲁斯摘要这项提议试图重建过去500万年上新世/更新世气候转变的大气二氧化碳，这将提供一个框架来测试上新世-更新世气候转变的可能原因。这一提议的主要目的是检验这样一种假设，即上新世早期暖期的变暖模式以及随后的降温模式是由二氧化碳的相应增加和减少所强迫的。PI‘s将通过重建藻类光合作用(EP)期间发生的总碳同位素分馏记录来评估PCO2的变化。该方法将提取和确定从全球分布的一组dsdp和dpp岩心获得的由触角生物衍生的长链酮生物标志物(烯酮)的碳同位素(D13C)值。此外，将从同一样本中分析一种或多种浮游有孔虫的碳同位素和镁/钙组成，以分别限制海水和表面温度的碳同位素组成的变化。烯酮的d13C与同时代的浮游近地表浮游有孔虫的d13C之间的差异代表了产生烯酮的浮游有孔虫在光合作用固碳过程中发生的大致的碳同位素分馏。这项技术已被用于重建新生代PCO2的变化幅度，被认为是目前可用的最可靠的古PCO2替代物之一。更广泛的影响包括两个美国主要机构之间的沿海合作，两名本科生和一名博士后参与了该项目，以及Pi Pagani参与了一个初中和高中教育项目，该项目将把这项研究的结果纳入到向该项目的学生和实习生的演示中。

Collaborative Research: Investigation of pCO2 Changes Since the Pliocene Based on Alkenone Carbon IsotopesMark Pagani/A. Christina RaveloYale University/UC Santa CruzAbstractThis proposal seeks to reconstruct atmospheric pCO2 across the Pliocene/Pleistocene climate transition of the last 5 million years, which will provide a framework to test possible causes of the Plio-Pleistocene climatic transition. The primary objective of this proposal is to test the hypothesis that the pattern of warming during the early Pliocene warm period, as well as the subsequent cooling, was forced by a corresponding increase and decrease in pCO2. The PI's will evaluate pCO2 changes by reconstructing records of the total carbon isotopic fractionation that occurs during algal photosynthesis (Ep). The approach will be to extract and determine the carbon isotopic (d13C) values of haptophyte-derived long-chain ketone biomarkers (alkenones) obtained from a globally distributed set of DSDP and ODP cores. In addition, the carbon isotopic and Mg/Ca composition of one or more species of planktonic foraminifers will be analyzed from the same sample to constrain changes in the carbon isotopic composition of seawater and surface temperatures respectively. The difference between the d13C of alkenones and of the coeval near-surface dwelling planktonic foraminifera represents the approximate carbon isotopic fractionation that occurs during photosynthetic carbon fixation specific to alkenone-producing haptophyte algae. This technique has been used to reconstruct the magnitude of pCO2 change during the Cenozoic and is considered one of the most reliable paleo- pCO2 proxies presently available. Broader impacts include the bi-coastal collaboration between two major U.S. institutions, participation in the project by two undergraduates and a post-doc, and PI Pagani's participatetion in a middle and high school education program that will incorporate the results of this study into presentations to students and interns in the program.