Collaborative Research: Do arc-continent collisions in the tropics set the Earth's climate state?

在其历史上，地球经历了温暖的无冰和寒冷的冰川气候，但尚不清楚这些背景气候状态之间的转变是否是二氧化碳来源或汇变化的结果。在这些数百万年的地质时间尺度上，二氧化碳主要通过火山放气进入海洋和大气，并主要通过岩石的化学侵蚀被清除，岩石通过河流将钙和镁输送到海洋，在那里它们与二氧化碳反应形成碳酸盐。据推测，海洋盆地的构造闭合和赤道纬度山脉的形成可能通过创造地形和侵蚀温暖潮湿热带地区高度可溶的海洋岩石来推动降温。这一过程增加了全球的耐风化性，从而增加了地球通过化学侵蚀将二氧化碳隔离在碳酸盐中的潜力。研究人员的目标是通过地质、地球化学和模型研究相结合的方法来检验这一假设，即全球气候变化已经控制了地球的背景气候状态。这项工作的这种更广泛的影响将通过在K-12和大学层面产生和传播关于地质气候变化的知识来造福社会。研究人员通过显生界开发了一个弧陆碰撞的全球数据库，标志着以前的海洋盆地的关闭，并用最先进的古地理模型重建了它们的位置。这一分析的结果揭示了全球最大的热带弧陆碰撞范围与显生界的每个主要冰期之间的时间上的重合。调查人员将在五个关键地带完善地质约束和构造重建。通过这些案例研究，研究人员将产生热年代学数据，完善新几内亚的折返历史，并构建新的阿尔卑斯-喜马拉雅带缝合古地理模型。调查人员还将获得从墨西哥到南美洲的二叠纪-石炭纪缝合带、阿巴拉契亚北部的奥陶系缝合带和阿拉伯-努比亚地盾的新元古代缝合带的新的地层学、地质年代学、地质学、岩石学、地球化学和古地磁数据。这些现场和实验室数据将与古地理、风化和气候模型结合起来，利用GEOCLIM模型框架对热带弧陆碰撞引起的二氧化碳变化进行估计。该框架将在不同二氧化碳浓度下运行的气候模型与全球风化模型相结合，从而可以使用可变气候学来估计全球风化模型变化对长期稳态二氧化碳水平的影响。在这个框架中，调查人员将进行敏感性测试，以隔离岩性或地形等特定参数的影响。研究人员将通过现代和古蛇绿岩流域的源汇阳离子研究进一步校准这些模型。最后，他们将开发统计方法来评估相关性的强度，并测试环境变化的假设因果机制。通过这项研究，研究人员将直接培养1名博士后研究员、5名博士生和众多本科生研究助理。为了传播这项基础研究，该团队将与K-12教师举行公开研讨会和研讨会，并在高中和本科阶段使用在线课程材料构建关于构造和气候的课程。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Over its history, Earth has experienced warm ice-free and cold glacial climates, but it is unknown if transitions between these background climate states were the result of changes in CO2 sources or sinks. On these multi-million year geological timescales, CO2 enters the ocean and atmosphere primarily by volcanic outgassing and is removed primarily though the chemical erosion of rocks, which delivers calcium and magnesium via rivers to the ocean where they react with CO2 to form carbonate. It is hypothesized that the tectonic closure of ocean basins and formation of mountains at equatorial latitudes could drive cooling by creating topography and eroding highly soluble oceanic rocks in the warm, wet tropics. This process increases global weatherability, thereby increasing Earth's potential to sequester CO2 in carbonates through chemical erosion. The investigators aim to test the hypothesis that changes in global weatherability have controlled the Earth's background climate state with coupled geological, geochemical, and modelling studies. This broader impact of this work will benefit society by generating and disseminating knowledge about geological climate change at both the K-12 and college level. The researchers have developed a global database of arc-continent collisions through the Phanerozoic, which mark the closure of former ocean basins, and reconstructed their position with state-of-the-art paleogeographic models. The results from this analysis revealed a temporal coincidence between the maximum global extent of arc-continent collision in the tropics and the occurrence of every major glacial period in the Phanerozoic. The investigators will refine geological constraints and tectonic reconstructions in five critical belts. Through these case studies, the researchers will generate thermochronological data and refine the exhumation history of New Guinea and construct a new paleogeographic model for suturing in the Alpine-Himalaya belt. The investigators will also acquire new stratigraphic, geochronological, geological, petrographic, geochemical, and paleomagnetic data along Permo-Carboniferous sutures from Mexico to South America, Ordovician sutures in the northern Appalachian, and Neoproterozoic sutures in the Arabian-Nubian Shield. These field and laboratory data will be integrated with paleogeographic, weathering, and climate models to develop estimates for the change in pCO2 resulting from arc-continent collisions in the tropics utilizing the GEOCLIM model framework. This framework integrates climate models run at varying pCO2 with global weathering models such that the variable climatology can be used to estimate the effect of changes in global weatherability model on long-term steady-state pCO2 levels. In this framework, the investigators will perform sensitivity tests to isolate the effects of specific parameters such as lithology or topography. The researchers will further calibrate these models with source-to-sink cation studies in modern and paleo ophiolite watersheds. Finally, they will develop statistical methods to evaluate the strength of correlation and test hypothesized causal mechanisms for environmental change. Through this research the investigators will directly train a postdoctoral researcher, 5 PhD students and numerous undergraduate research assistants. To disseminate this basic research, the team will hold public seminars and workshops with K-12 teachers, and construct classes on Tectonics and Climate with online course materials, both at the high-school and undergraduate level.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.