Numerical Modeling of the Greenhouse-Icehouse Transition: Eocene-Oligocene Boundary

目前可用的数值模式不足以研究生物圈历史上最重要的事件。其中一个事件是大约3400万年前始新世-渐新世边界从温室到冰室条件的重大转变，南极洲第一次建立了大冰盖和其他全球气候重组。这些事件发生在几十万年到几百万年的时间尺度上，并且本质上是时间连续的，长期成分（例如，冰盖，二氧化碳）取决于和反馈的短期准平衡成分（大气，海洋上层）的当前状态。全球海洋地球化学循环的箱式模型对于研究海洋、大气和生物区系的长期演变很有用，而海洋-大气环流耦合模型对于研究几种平衡状态和十年至百年气候变化是理想的。然而，这些工具都无法模拟重要的长期事件和感兴趣的过渡，并具有足够的空间和时间分辨率，以提供可测试的预测。该项目将联合收割机长期地球化学成分与为长期物理气候模拟开发的新的可用耦合技术相结合，对始新世-渐新世过渡进行首次空间和时间分辨的地球化学调查。耦合技术包括A/OGCM解的矩阵查找表和异步驱动由R。DeConto和D.其他NSF资助项目的Pollard。生物地球化学成分已被L. Kump和合作者，包括二维陆地风化和OGCM地球化学。最近，J. Zachos和L. Kump在跨越E-O过渡的几百万年中应用了这些组件的盒子模型版本。他们发现，地球化学反馈可以与物理气候系统产生重要的相互作用，导致过渡后的超调和百万年的振荡，如在海底-18O记录中观察到的那样。使用新的耦合技术和2-D/3-D模型，我们将测试有关E-O转变之前、期间和之后的事件的五个具体假设。我们将比较和验证结果对广泛的和时间分辨的古海洋学数据，增强了陆地代理：-底栖氧和碳同位素记录约束底层水温度加上冰量，平均海洋同位素组成和深盆梯度; - Mg/Ca记录的温度; -层序地层记录被动边缘进一步约束海平面; -大气CO2的地质约束;- 陆地风化强度、速率和海洋输入的指标。一个本科生（做她的毕业论文）和一个研究生将参与这项研究，与本科生主要集中在我们的假设之一，关于陆架盆地碳酸盐沉积分区。我们将促进数值模拟专业知识的传播，在本项目的资助间隔期间在宾夕法尼亚州立大学举办夏季研讨会，由全球大学网络（WUN;wun.ac.uk）赞助。第一次WUN-SIES/TA研讨会的主题是深时研究中的建模和数据解释，主要面向研究生，博士后和早期职业地球科学专业人员。L. Kump在WUN赞助的宾夕法尼亚州立大学活动中发挥了重要作用，包括每月的视频研讨会、研究生交流和研讨会。通过WUN，参与该项目的学生将有机会前往南安普顿（英国）与他们的气候建模小组合作。

EAR-0652020KUMPCurrently available numerical models are inadequate for the study of the most important events in the history of the biosphere. One such event is the major transition from Greenhouse to Icehouse conditions at the Eocene-Oligocene boundary ~34 million years ago, with the first establishment of a large ice sheet on Antarctica and other worldwide climate reorganizations. Such events have taken place over time scales of a few hundred thousand to millions of years, and are inherently time continuous, with drastic changes in long-term components (e.g., ice sheets, CO2) depending on and feeding back on the current state of short-term quasi-equilibrium components (atmosphere, upper ocean). Box models of global biogeochemical cycles are useful for studying long-term evolution of the oceans, atmosphere and biota, while coupled ocean-atmosphere general circulation models are ideal for studying a few equilibrium states and decadal to centennial climate change. However, none of these tools is able to simulate important long-term events and transitions of interest with adequate spatial and temporal resolution to provide testable predictions.Intellectual Merit. This project will combine long-term biogeochemical components with newly available coupling techniques developed for long-term physical climate modeling, to perform the first spatially and temporally resolved biogeochemical investigation of the Eocene-Oligocene transition. The coupling techniques involve a matrix look-up table of A/OGCM solutions and asynchronous driving of a 3-D ice sheet model, developed by R. DeConto and D. Pollard in other NSF-funded projects. The biogeochemical components have been developed and used extensively by L. Kump and collaborators, and include 2-D land weathering and OGCM biogeochemistry. Recently J. Zachos and L. Kump have applied box-model versions of these components through several million years spanning the E-O transition. They found that biogeochemical feedbacks can have important interactions with the physical climate system, resulting in post-Transition overshoots and million-year oscillations as observed in benthic -18O records. Using the new coupling techniques and 2-D/3-D models, we will test five specific hypotheses concerning events leading up to, during and after the E-O transition. We will compare and validate results against extensive and temporally resolved paleoceanographic data, augmented by terrestrial proxies: - Benthic oxygen and carbon isotopic records constraining bottom-water temperatures plus ice volume, mean ocean isotopic composition and deep basin gradients; - Mg/Ca records for temperature; - Sequence stratigraphic records on passive margins further constraining sea level; - Geologic constraints on atmospheric CO2; - Proxies for terrestrial weathering intensities, rates, and inputs to the ocean.Broader Impacts. One undergraduate (doing her senior thesis) and one graduate student will be involved in this research, with .the undergraduate focusing primarily on one of our hypotheses concerning shelf-basin partitioning of carbonate deposition. We will facilitate the dissemination of numerical modeling expertise by holding a summer workshop at Penn State during the funding interval of this project, sponsored by the Worldwide Universities Network (WUN;wun.ac.uk). The theme of this first WUN-SIES/TA workshop will be on modeling and data interpretation in deep-time studies, primarily for graduate students, postdocs, and early-career Earth science professionals. L. Kump has been instrumental in WUN-sponsored activities at Penn State, including monthly video seminars, graduate student exchanges and workshops. Through WUN, students involved in this project will have the opportunity to travel to Southampton (UK) to work with their climate modeling group.