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

目前，由于人类活动，如化石燃料燃烧，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100万年的冰河时代。海洋被认为在冰河时期大气CO2变化中发挥了关键作用，因为海洋吸收的CO2有助于全球变冷，海洋释放的CO2有助于变暖。重建过去海洋二氧化碳循环的最有用工具之一是碳的放射性同位素14 C。放射性碳是在记录海水14 C的海洋微化石中测量的。这项研究将从海洋沉积物岩心中开发微体化石14 C记录，并利用它们来揭示在末次冰期最大期（大约20，000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有助于提高我们对过去海洋-大气CO2交换的认识，从而有助于我们预测大气CO2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。拟议的工作将使用一套新的沉积物14 C/记录沿着东北太平洋边缘，以解决一个长期存在的古海洋学问题-什么是在冰消期东北太平洋异常低的14 C的起源？这一特征也被解释为以下证据：（i）一个异常低的海水14 C/C平流到北太平洋东部的网站，（ii）本地或区域添加低14 C碳从海底火山活动，或（iii）沉积后的代用记录的改变。拟议的分析将产生四个新的底栖有孔虫14 C/C记录从东北太平洋核心网站上游的网站与冰消期14 C异常低。这些记录将与底栖有孔虫d18 O记录同步，并将用于创建北太平洋东部冰消期海水14 C的新地图。该图将用于区分低14 C信号的平流源和本地源。这项研究将支持在加州大学欧文分校（少数民族服务机构）的本科生的培训。该项目还将支持组织一个为期3天的研讨会，为来自当地高中的未来第一代大学生提供高代表性的少数民族人口，目的是提高代表性不足的少数民族在地球科学中的参与。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智力价值和更广泛的影响审查标准进行评估来支持。

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.