Eastern Pacific carbon chemistry after the ice age: gaining insight to a persistent carbon cycle mystery

由于燃烧化石燃料等人类活动，目前大气中二氧化碳（CO2）的增加正在使地球变暖。更好地预测未来气候的一种方法是研究过去大气中二氧化碳的自然变化。这种变化发生在过去100万年的冰河时期。海洋被认为在冰河时期大气中二氧化碳的变化中发挥了关键作用，因为海洋吸收二氧化碳导致全球变冷，而海洋释放二氧化碳导致全球变暖。重建过去海洋二氧化碳循环最有用的工具之一是碳的放射性同位素14C。放射性碳是在海洋微化石中测量的，它记录了海水的14C。这项研究将开发海洋沉积物岩心的微化石14C记录，并利用它们来揭示末次盛冰期（大约2万年前）发生在北太平洋东部的低放射性碳异常的原因。了解这一异常现象将提高我们对过去海洋-大气二氧化碳交换的认识，从而有助于我们预测大气二氧化碳上升对未来气候的影响。该项目将支持加州大学欧文分校的本科生参与研究。该项目还包括支持一系列旨在向未来的第一代大学生介绍地球科学的讲习班。这项工作将利用北太平洋东部边缘的一组新的沉积物14C/记录来解决一个长期存在的古海洋学问题——在冰川消退期间，北太平洋东部异常低的14C的来源是什么？这一特征被解释为：(i)异常低的海水14C/C平流到北太平洋东部，（ii）海底火山作用在局部或区域增加了低14C碳，或（iii）代用记录的沉积后蚀变。所提出的分析将产生四个新的底栖有孔虫14C/C记录，这些记录来自北太平洋东部冰期14C异常低的地点上游的核心地点。这些记录将与底栖有孔虫d18O记录同步，并将用于创建北太平洋东部冰川海水14C的新地图。这张图将用于区分低14c信号的平流源和本地源。这项研究将支持加州大学欧文分校（少数族裔服务机构）的本科生培训。该项目还将支持组织一个为期3天的讲习班，面向来自少数族裔人数较少的当地高中的未来第一代大学生，目的是增加少数族裔在地球科学领域的参与。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。

The current rise in atmospheric carbon dioxide (CO2) due to human activities such as fossil fuel burning is warming the planet. One way to better predict future climate is to study past natural changes in atmospheric CO2. Such changes occurred through the ice ages of the past 1 million years. The ocean is thought to have played a key role in ice age atmospheric CO2 changes because ocean uptake of CO2 contributes to global cooling and CO2 release by the ocean contributes to warming. One of the most useful tools for reconstructing past ocean CO2 cycles is the radioactive isotope of carbon, 14C. Radiocarbon is measured in marine microfossils which record the 14C of seawater. This study will develop microfossil 14C records from ocean sediment cores and use them to unravel the causes of a low-radiocarbon anomaly that occurred in the eastern North Pacific Ocean at the time of the Last Glacial Maximum (roughly 20,000 years ago). Understanding this anomaly will improve our knowledge of ocean-atmosphere CO2 exchange in the past, and thus will help us predict the impact of rising atmospheric CO2 on future climate. The project will support research participation by undergraduate students at UC Irvine. The project also includes support for a series of workshops designed to introduce prospective First Generation college students to the Earth Sciences.The proposed work will use a set of new sediment 14C/ records along the Eastern North Pacific margin to address a long-standing paleoceanographic question—what is the origin of the anomalously low 14C in the Eastern North Pacific during the deglaciation? This feature has alternately been explained as evidence for: (i) an anomalously low seawater 14C/C advected to the eastern North Pacific sites, (ii) the local or regional addition of low-14C carbon from seafloor volcanism, or (iii) post-depositional alteration of the proxy record. The proposed analyses will yield four new benthic foraminifera 14C/C records from Eastern North Pacific core sites upstream of the sites with anomalously low deglacial 14C. These records will be synchronized using benthic foraminifera d18O records and will be used to create a new map of Eastern North Pacific deglacial seawater 14C. This map will be used to distinguish between advected and local sources for the low-14C signal. The study will support the training of undergraduate students at UC Irvine (a Minority Serving Institution). The project will also support organization of a 3-day workshop for prospective First Generation college students from local high schools with high under-represented minority populations, with the goal of increasing the participation of under-represented minorities in the Earth Sciences.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.