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

古新世-始新世最高温度(PETM)是5500万年前发生的一次强烈变暖事件。当时PETM是由向海洋和大气中大量增加的二氧化碳推动的。该项目将量化PETM二氧化碳的增加，并记录地球碳循环对该增加的反应。这项研究将探索地球系统如何对气候扰动做出反应，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在快速变暖时的气候、水文和地球化学演变。因此，这项研究将提供与现代气候变化和未来气候的有价值的比较。该项目更广泛的影响包括对研究生和本科生研究人员的支持。该项目还将创建YouTube视频内容用于本科生课程。这项研究将利用钙同位素作为记录器，记录在PETM恢复期间底层水方解石饱和状态的时间演变。与开始和海洋酸化阶段相比，PETM恢复期间受到的关注较少。了解恢复间隔的动态是至关重要的，因为这是硅酸盐风化对气候变暖的响应表现出来的时间，主要是碱度“超调”。这段时间段是一个有利的研究重点，因为它比强烈的碳酸盐溶解时间段更有可能在海洋沉积物中被记录和保存。互补的数值模拟方法-反应输运(RTM)和中等复杂性地球系统(CGENIE)模拟-以及现有的海洋溶解无机碳(DIC)重建将用于阐明(I)输入到海洋-大气系统的碳的量，以及(Ii)硅酸盐的风化反应。这种方法的一个显著优点是，解释框架不受碳注入速度的影响(即，对于最有可能的注入时间尺度为10ka)，消除了在重建碳注入质量方面的重大不确定性。地球系统从高温中恢复的速度关键取决于硅酸盐风化反馈的运行速度和反馈的强度。尽管这些知识很重要，但几乎没有什么约束条件可以用来将不确定性降到最低。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。

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.