OCE-PRF Unraveling Southern Hemisphere westerly wind variability through the last ~150 ky using Tasman Sea sediments

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。南半球的西风，通常被称为“西风”，在区域和全球气候中起着至关重要的作用。现代观测表明，这些风正在向南极洲移动，并且由于人为变暖而变得更强。这些风的位置和强度的变化可能会影响海洋环流、自然和人为气溶胶的分布以及碳循环。因此，更好地了解地球上的条件与今天不同时西风是如何变化的，对于加强我们对其未来变化的限制至关重要。这里提出的研究旨在重建过去15万年中南半球西风带在比现在更冷或更暖的气候状态下的特征。为了实现这一目标，PI Abell将利用塔斯曼海几个岩心的海洋沉积物，开发粉尘通量、海面温度和澳大利亚植被状况的记录。只有将这些与西风有关的独立代用物结合起来，再加上覆盖南北~10°样带的多个采样岩心，才能确定南半球西风的位置和强度。作为NSF博士后研究员，PI Abell将通过几个项目指导高中生和本科生。其中之一是南亚利桑那研究、科学和工程基金会的S.T.A.R实验室项目，在那里他将指导一名当地高中生开发和执行与这项拟议研究相关的研究项目。此外，PI Abell将与亚利桑那大学的一名本科生合作，通过Ronald E. McNair成就计划为他们的研究生院做准备。该项目将重点重建过去~150天不同气候状态下南半球西风的特征。PI Abell将利用塔斯曼海横跨约10°纬度的三个海洋沉积物岩心样本，以及四种独立的（有机和无机）地球化学方法，研究西风带的位置和强度的变化。具体而言，PI Abell将：(1)基于无机沙尘代理生成恒定通量代理衍生的沙尘通量记录；(2)使用正构烷烃作为沙尘代理，开发不受火山输入影响的沙尘通量的附加记录；(3)生成植物蜡碳同位素记录，获得澳大利亚C3/C4植被边界信息，进而获得降水季节性信息；(4)利用alkenone UK’37海温代理，重建亚热带和塔斯曼锋的移动。综合这些不同的代用资料，可以重建全新世、末次极大冰期和末次间冰期等关键气候时期南半球西风带的位置和强度。这些数据集将对气候模拟界有用，因为它们将提供西风带自然变率对潜在驱动机制（如冰量和大气温度梯度）变化的约束，从而有助于西风未来变化的基本模拟。从这项工作中得出的解释和结论将通过非技术设置，如图森图书节科学中心的公开演讲和演讲/活动，向公众展示。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The Southern Hemisphere westerly winds, commonly referred to as the “westerlies”, play a crucial role in regional and global climate. Modern observations suggest that these winds are moving towards Antarctica and becoming stronger in response to anthropogenic warming. Shifts in the position and intensity of these winds can potentially impact ocean circulation, the distribution of natural and anthropogenic aerosols, and the carbon cycle. As such, developing a better understanding of how the westerly winds change when conditions on Earth were different from today is critical to enhancing our constraints on their future variability. The research proposed here seeks to reconstruct the characteristics of the Southern Hemisphere westerlies during climate states both colder and warmer than today over the last 150,000 years. To accomplish this, PI Abell will develop records of dust fluxes, sea-surface temperatures, and Australian vegetation regimes utilizing marine sediments from several cores in the Tasman Sea. It is the combination of these independent proxies related to the westerly winds, along with sampling multiple cores that cover an ~10° north-south transect, that will allow for information on both the position and strength of the Southern Hemisphere westerlies to be ascertained. As an NSF Postdoctoral Fellow, PI Abell will mentor high school and undergraduate students through several programs. One of these is the Southern Arizona Research, Science, and Engineering Foundation S.T.A.R Labs Program, where he will guide a local high school student through developing and executing a research project related to this proposed research. Additionally, PI Abell will work with a University of Arizona undergraduate student to prepare them for graduate school through the Ronald E. McNair Achievement Program. The proposed project will focus on reconstructing the characteristics of the Southern Hemisphere westerly winds during various climate states over the last ~150 ky. PI Abell will utilize samples from three marine sediment cores spanning ~10° latitude in the Tasman Sea, along with four independent (organic and inorganic) geochemical methods, to investigate shifts in the position and intensity of the westerlies. Specifically, PI Abell will 1) produce constant flux proxy-derived dust flux records based on inorganic dust proxies, 2) use n-alkanes as a dust proxy to develop additional records of dust fluxes that are not influenced by volcanic inputs, 3) generate records of plant-wax carbon isotopes to gain information on C3/C4 vegetation boundaries, and in turn precipitation seasonality, in Australia, and 4) reconstruct shifts in the Subtropical and Tasman Fronts by utilizing the alkenone UK’37 SST proxy. Combined, information from these various proxies will allow for the reconstruction of both the position and intensity of the Southern Hemisphere westerlies during key climatic intervals such as the Holocene, the Last Glacial Maximum, and the last interglacial period. These datasets will be useful to the climate modeling community, as they will provide constraints on the natural variability of the westerlies to changes in potential driving mechanisms such as ice volume and atmospheric temperature gradients, thus aiding essential modeling of future changes in the westerly winds. Interpretations and conclusions drawn from this work will be brought to the public via non-technical settings such as public talks and presentations/activities at The Science Center at the Tucson Festival of Books.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.