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

年际气候变化主要受厄尔尼诺南方涛动(ENSO)的影响。ENSO被表示为热带太平洋海面温度的变化，它影响着全球的自然和人类系统。ENSO事件在未来是否会变得更强尚不清楚，部分原因是控制ENSO的过程还没有完全了解。利用赤道东太平洋海洋沉积物的地球化学替代证据，可以重建过去的ENSO活动。最后一个暖气候期，即海洋同位素阶段5e(MIS5e)，发生在11.9万-12.6万年前。因此，来自MIS5E的东太平洋沉积物记录了前一个暖态期间的ENSO行为。这项研究将利用有孔虫的壳层化学特征来描述赤道东太平洋沉积岩芯的MIS5e沉积物。这些新记录将为沉积岩芯提供可靠的年龄控制。然后，可以将来自该岩心的数据与来自其他地点的古气候数据进行比较。这项研究将通过有意义的本科生研究机会，支持扩大对STEM和地球科学的参与的外展努力。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工作坊的关键组成部分。这将给学生提供关于现代分析技术的宝贵经验。由于我们对控制热带太平洋变率的机制的了解还不完整，ENSO对大气中二氧化碳浓度升高的反应没有受到很好的约束。以前暖期，特别是最后一次间冰期(MIS5e)的ENSO重建是有限的。这样的重建将能够测试ENSO与不断变化的气候背景条件、轨道强迫以及在没有现代二氧化碳强迫的情况下的季节变化的关系。赤道东太平洋冷舌区是ENSO的活动中心，但具有足够物质、分辨率和特征的沉积岩芯很少。这项研究将利用表层和地下有孔虫产生稳定的同位素和痕量元素地层学，以识别和表征赤道东太平洋沉积核心中的MIS5e沉积物。生成跨越最后一次冰川盛期至MIS5E的长期表层和地下地层学，将允许对沉积物的成分、累积速率和分辨率进行表征，从而能够使用有孔虫地球化学指标对热带太平洋的可变性进行未来的高分辨率分析，并允许测试ENSO控制的关键假设。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。

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.