Collaborative Research: Studying Carbon Injection and the Silicate Weathering Feedback over the Paleocene Eocene Thermal Maximum Using Ca Isotopes and Modeling

古新世-始新世最热期（PETM）是发生在5500万年前的一次强烈的变暖事件。PETM是由当时海洋和大气中大量增加的二氧化碳驱动的。该项目将量化PETM二氧化碳的增加，并记录地球碳循环对这种增加的反应。这项研究将探讨地球系统如何对气候扰动作出反应，包括这种反应的速度和机制。地质记录中的事件显示了地球对快速变暖的气候、水文和地球化学演变。因此，这项研究将为现代气候变化和未来气候提供有价值的比较。该项目更广泛的影响包括支持一名研究生和本科生研究人员。该项目还将创建YouTube视频内容用于本科课程。这项研究将利用钙同位素作为记录器的时间演变的底层水方解石饱和度状态的恢复间隔的PETM，间隔已收到较少的关注相比，发病和海洋酸化阶段。了解动态的恢复间隔是至关重要的，因为这是在此期间，硅酸盐风化对气候变暖的反应表示，主要是作为一个碱度的“过冲”。这段时间是一个有利的研究重点，因为它比强烈的碳酸盐溶解的时间更有可能被记录和保存在海洋沉积物中。互补的数值模拟方法-反应性运输（RTM）和中等复杂性地球系统（cGENIE）建模-和现有的海洋溶解无机碳（DIC）的重建将用于阐明（i）海洋-大气系统的C输入量，和（ii）硅酸盐风化响应。这种方法的一个显著优点是解释框架不受碳注入速率的影响（即，对于最可能的注入时间尺度10 ka），从而消除了重建碳注入质量中的显著不确定性。地球系统从高温中恢复的速度主要取决于硅酸盐风化反馈作用的速度和反馈的强度。尽管这些知识意义重大，但很少有限制因素可以最大限度地减少不确定性。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The Paleocene-Eocene Thermal Maximum (PETM) was a strong warming event that took place 55 million years ago. The PETM was driven by a large addition of carbon dioxide to the ocean and atmosphere at that time. This project will quantify the PETM carbon dioxide addition and document the response of the Earth’s carbon cycle to that addition. The study will explore how the Earth system responds to climatic perturbations, including the rates and mechanisms of that response. Events in the geologic record show the climatic, hydrological, and geochemical evolution of the Earth in response to rapid warming. Thus, this study will provide a valuable comparison with modern climate change and future climate. The project broader impacts include support for a graduate student and undergraduate researchers. The project will also create YouTube video content for use in undergraduate courses.This study will utilize Ca isotopes as recorders of the temporal evolution of bottom water calcite saturation state over the recovery interval of the PETM, an interval that has received less attention in comparison to the onset and ocean acidification phases. Understanding the dynamics of the recovery interval is critical because this is the time during which the silicate weathering response to climatic warming is expressed, primarily as an alkalinity 'overshoot'. This interval is a favorable focus for study because it is more likely than the interval of intense carbonate dissolution to be recorded, and preserved, in marine sediments. Complementary numerical modeling approaches – reactive transport (RTM) and intermediate complexity Earth System (cGENIE) modeling – and existing reconstructions of oceanic dissolved inorganic carbon (DIC) will be used to elucidate (i) the amount of C input to the ocean-atmosphere system, and (ii) the silicate weathering response. A significant advantage of this approach is that the interpretive framework is not impacted by the rate of carbon injection (i.e., for the most likely injection time scales 10 ka), removing a significant uncertainty in reconstructing the mass of carbon injection. The rate at which the Earth System recovers from hyperthermals depends critically on the rate at which the silicate weathering feedback operates and the strength of the feedback. Despite the significance of this knowledge, there are few constraints available to minimize uncertainties.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.