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

冰河时代后的东太平洋碳化学：深入了解持久的碳循环之谜

• 批准号: 2015647
• 负责人: Patrick Rafter
• 金额: $ 32.61万
• 依托单位: University of California-Irvine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2015647&HistoricalAwards=false
• 关键词: Eastern; Pacific; carbon; chemistry; after

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.

目前，由于化石燃料燃烧等人类活动，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。这些变化发生在过去100万年的冰河时代。海洋被认为在冰河时代大气二氧化碳变化中发挥了关键作用，因为海洋吸收二氧化碳有助于全球变冷，海洋释放二氧化碳有助于变暖。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，这些化石记录了海水的14C。这项研究将开发来自海洋沉积岩心的微化石14C记录，并用它们来揭示上一次冰川盛期(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。了解这种异常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研讨会。拟议的工作将使用东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--在冰川消融期间，东北太平洋东部异常低的14C的起源是什么？这一特征也被解释为以下证据：(I)异常低的海水14C/C平流到北太平洋东部，(Ii)来自海底火山活动的局部或区域低14C碳添加，或(Iii)代理记录的沉积后改变。拟议的分析将在脱冰期14C异常低的地点上游的东北太平洋核心地点产生4个新的底栖有孔虫14C/C记录。这些记录将使用底栖有孔虫d18O记录进行同步，并将用于创建北太平洋东部脱冰期海水14C的新地图。这张图将用于区分低14C信号的平流源和局地源。这项研究将支持加州大学欧文分校(一家少数民族服务机构)对本科生的培训。该项目还将支持为来自少数民族人口比例较高的当地高中的潜在第一代大学生组织一个为期3天的研讨会，目标是增加未被代表性的少数民族参与地球科学。该奖项反映了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。