Core Stratigraphy and Paleotemperature Estimates to Characterize Last Interglacial Tropical Pacific Climate Variability and El Nino Southern Oscillation During MIS 5e

年际气候变率主要受厄尔尼诺南方涛动（ENSO）影响。厄尔尼诺/南方涛动表现为热带太平洋海面温度的变化，它影响着地球仪的自然和人类系统。目前还不清楚ENSO事件未来是否会变得更强，部分原因是控制ENSO的过程尚未完全了解。过去的ENSO活动可以重建地球化学代用证据从赤道东太平洋的海洋沉积物。最后一个温暖的气候时期，被称为海洋同位素阶段5e（MIS 5e），发生在大约119，000 - 126，000年前。因此，东太平洋沉积物从MIS 5e记录ENSO行为在以前的温暖状态。这项研究将使用有孔虫的壳化学来表征赤道东太平洋沉积物芯中MIS 5e沉积物。这些新记录将为沉积物岩心提供可靠的年龄控制。从这个核心的数据，然后可以与其他地点的古气候数据进行比较。该研究将支持外联工作，通过有意义的本科生研究机会，扩大对STEM和地球科学的参与。本科生研究助理将参与该项目的所有阶段。地球化学分析将是本科生暑期讲习班的一个关键组成部分。这将为学生提供现代分析技术的宝贵经验。由于我们对控制热带太平洋变化的机制的理解还不完全，ENSO对大气二氧化碳浓度升高的反应还没有得到很好的限制。ENSO在以往温暖时期，特别是末次间冰期（MIS 5e）的重建是有限的。这种重建将能够在没有现代二氧化碳强迫的情况下测试ENSO与不断变化的气候背景条件、轨道强迫和季节变化的关系。赤道东太平洋冷舌区是ENSO的作用中心，但具有足够的材料，分辨率和特征的沉积物芯稀少。这项研究将产生一个稳定的同位素和微量元素地层使用表面和地下有孔虫识别和表征MIS 5e沉积物在赤道东太平洋沉积物芯。生成从末次盛冰期到MIS 5e的长期地表和地下地层，将使沉积物的成分、积累速率和分辨率得到表征，从而能够在未来利用有孔虫地球化学代用指标对热带太平洋变化进行高分辨率分析，该奖项反映了NSF的法定使命，并被认为是值得通过评估来支持的使用基金会的知识价值和更广泛的影响审查标准。

Inter-annual climate variability is dominated by the El Niño Southern Oscillation (ENSO). ENSO is expressed as changes in tropical Pacific sea surface temperatures, and it impacts natural and human systems across the globe. Whether ENSO events will become stronger in the future is unclear, in part because the processes that control ENSO are not fully understood. Past ENSO activity can be reconstructed using geochemical proxy evidence from ocean sediments from the eastern equatorial Pacific. The last warm climate period, known as Marine Isotope Stage 5e (MIS 5e), occurred ~119,000-126,000 years ago. Thus, Eastern Pacific sediments from MIS 5e record ENSO behavior during a previous warm state. This research will characterize MIS 5e sediments in an eastern equatorial Pacific sediment core using the shell chemistry of foraminifera. These new records will provide reliable age control for the sediment core. The data from this core can then be compared with paleoclimate data from other locations. The study will support outreach efforts to broaden participation in STEM and in the geosciences through meaningful undergraduate research opportunities. Undergraduate research assistants will be involved in all phases of the project. The geochemical analyses will be a key component of a summer workshop for undergraduates. This will give the students valuable experience on modern analytical techniques. ENSO’s behavior in response to elevated atmospheric carbon dioxide is not well constrained as our understanding of the mechanisms controlling tropical Pacific variability is incomplete. Reconstructions of ENSO during previous warm periods, and in particular the last interglacial (MIS 5e) are limited. Such reconstructions would enable testing of ENSO’s relationship with changing climate background conditions, orbital forcing, and seasonal changes in the absence of modern carbon dioxide forcing. The eastern equatorial Pacific cold tongue region is a center-of-action for ENSO, but sediment cores with adequate material, resolution, and characteristic are sparse. This research will generate a stable isotope and trace elemental stratigraphy using surface and subsurface foraminifera to identify and characterize MIS 5e sediments in an eastern equatorial Pacific sediment core. Generation of a long-term surface and subsurface stratigraphy spanning the last glacial maximum to MIS 5e will allow the sediments to be characterized for composition, accumulation rates and resolution, enabling future, high-resolution analysis of tropical Pacific variability using foraminiferal geochemical proxies, and allow for testing of key hypotheses of ENSO control.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.