P2C2: Collaborative Research: The consumption rate of a CO2 pulse: Lessons from the middle Miocene

由于人类活动产生的大气二氧化碳浓度已经超过了地球过去300万年历史上已知的最高水平，因此对社会来说，更好地了解化石燃料燃烧和其他人类活动产生的大气二氧化碳的命运至关重要。对未来气候情景的更准确预测，需要更详细地了解自然过程从地球大气中去除工业时代社会产生的二氧化碳脉冲的速度有多快。这些过程的模型预测了人类产生的二氧化碳脉冲的长尾，表明这些碳将对我们的气候和社会产生长期影响。由于这些过程在相对较长的时间尺度上进行，这些预测可以通过查看过去事件的地质记录来验证。这个项目将提供一个高分辨率的重建，一个古老的自然脉冲的二氧化碳注入到大气中是如何被地球系统中和的地质过去。因此，这项研究将提供从过去到现在大气中碳被自然过程吸收的速率的重要视角，从而帮助地球科学家对未来的气候变化做出更准确的预测。研究人员还将与一个面向高中生的地球科学夏令营合作，非科学专业的本科生将参加有关气候变化影响的实地体验学习。这两项活动都将有助于将不同背景的学生带入STEM和地球科学的职业道路。这项研究将评估美国太平洋西北部哥伦比亚河玄武岩群火山爆发期间大量二氧化碳注入大气的快速脉冲后，大气二氧化碳在年代际尺度上的演变。与此同时，在爱达荷州北部附近，玄武岩流可能阻塞了当地的排水系统，形成了一个古老的湖泊（中新世克拉基亚湖）。在新形成的克拉基亚湖中开始积聚的沉积物保存了地质记录中这些事件的历史，可以用来以高分辨率评估火山爆发导致的大气二氧化碳浓度峰值的演变。研究人员将使用微量xrf扫描元素分布，将他们的研究重点放在未氧化的样沉积物上。他们将利用保存在沉积物中的化石叶片气孔的特性，结合保存在化石有机质中的碳的稳定同位素的信息，重建这种自然的二氧化碳脉冲的演变。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

As human activity has already produced atmospheric carbon dioxide concentrations that have surpassed the highest levels known during of the past three million years of Earth history, it is critical for society to better understand the fate of atmospheric carbon dioxide produced by fossil fuel burning and other human activities. More accurate projections of future climate scenarios will require a more detailed understanding of how fast natural processes can remove from Earth's atmosphere the pulse of carbon dioxide that is being produced by society in the industrial era. Models of these processes predict a long tail of the pulse of human-produced carbon dioxide, suggesting that this carbon will have a long-term impact on our climate and society. As these processes play out over relatively long timescales, such predictions can be verified by looking to the geological record of past events. This project will provide a high-resolution reconstruction of how an ancient natural pulse of carbon dioxide injected into the atmosphere was neutralized by the Earth system in the geological past. As such, this study will provide important perspective from the past on the present rate at which atmospheric carbon can be taken up by natural processes, and hence help Earth scientists make more accurate projections of future climate change. The researchers will also work with a Geoscience summer residence camp for high school students and non-science major undergraduate students will participate in experiential learning in the field on the impact of climate change. Both activities will contribute to bringing students with diverse backgrounds into STEM and geoscience career paths.This research will evaluate the evolution of atmospheric CO2 on decadal timescales following a rapid pulse of large amounts of carbon dioxide injected into the atmosphere during volcanic eruptions that was part of the Columbia River Basalt Group in the US Pacific Northwest. At the same time as these eruptions and nearby in northern Idaho, an ancient lake (Miocene Lake Clarkia) was formed when basalt flows presumably dammed a local drainage system. Sediments that began to accumulate in the newly formed Lake Clarkia preserve a history of these events in the geological record that can be used to evaluate, in high-resolution, the evolution of the spike of atmospheric CO2 concentrations that resulted from the volcanic eruptions. The researchers will use micro-XRF scanning of elemental distributions to focus their study on the unoxidized, varve-like sediments. They will reconstruct the evolution of this natural pulse of CO2 using the properties of stomatal pores in fossil leaves preserved in the sediments, combined with information from the stable isotopes of carbon preserved in the fossil organic matter.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.