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窖条件的重大转变，伴随着南极洲大冰盖的首次建立和其他全球气候重组。这些事件发生在几十万年至数百万年的时间尺度上，并且具有内在的时间连续性，长期成分（如冰盖、二氧化碳）的剧烈变化取决于短期准平衡成分（大气、上层海洋）的当前状态，并对其进行反馈。全球生物地球化学循环的箱型模式可用于研究海洋、大气和生物群的长期演变，而耦合的海洋-大气环流模式则适用于研究少数平衡状态和年代际至百年气候变化。然而，这些工具都不能模拟重要的长期事件和具有足够空间和时间分辨率的转换，以提供可测试的预测。知识价值。该项目将长期生物地球化学成分与最新开发的长期物理气候模拟耦合技术相结合，对始新世-渐新世过渡进行首次时空分辨率的生物地球化学调查。耦合技术包括a /OGCM解决方案的矩阵查找表和三维冰盖模型的异步驱动，该模型由R. DeConto和D. Pollard在其他nsf资助的项目中开发。生物地球化学成分由L. Kump等人开发并广泛应用，包括2-D陆地风化和OGCM生物地球化学。最近，J. Zachos和L. Kump应用了这些组件的盒子模型版本，跨越了数百万年的E-O转换。他们发现，生物地球化学反馈可以与物理气候系统产生重要的相互作用，导致过渡期后的超调和百万年的振荡，正如在底栖生物-18O记录中观察到的那样。利用新的耦合技术和2-D/3-D模型，我们将测试关于E-O过渡之前、期间和之后事件的五个具体假设。我们将与广泛的、暂时解决的古海洋学数据进行比较并验证结果，并辅以陆地代用指标：—底栖生物的氧和碳同位素记录限制了底水温度和冰体积、平均海洋同位素组成和深盆地梯度；-温度Mg/Ca记录；-被动边缘的层序地层记录进一步限制了海平面；-对大气二氧化碳的地质限制；-陆地风化强度、速率和对海洋的影响的代用物。更广泛的影响。一名本科生（做她的毕业论文）和一名研究生将参与这项研究。本科生主要关注我们关于碳酸盐沉积的陆架-盆地划分的假设之一。在世界大学网络（WUN; WUN .ac.uk）的资助下，我们将在宾夕法尼亚州立大学举办夏季研讨会，以促进数值模拟专业知识的传播。第一次WUN-SIES/TA研讨会的主题将是深度时间研究中的建模和数据解释，主要面向研究生、博士后和早期地球科学专业人员。L. Kump在宾夕法尼亚州立大学wun赞助的活动中发挥了重要作用，包括每月的视频研讨会、研究生交流和讲习班。通过WUN，参与该项目的学生将有机会前往南安普顿（英国）与他们的气候模拟小组一起工作。

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.