Collaborative Research: Determining climate related changes in water mass structure, paleoventilation, and paleocirculation in the Southeast Indian and Southern Oceans

合作研究：确定东南印度洋和南大洋与气候相关的水团结构、古通风和古环流变化

• 批准号: 2230999
• 负责人: Ellen Martin
• 金额: $ 34.97万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-01 至 2026-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2230999&HistoricalAwards=false
• 关键词: Collaborative; Research; Determining; climate; related

Today fifty times more CO2 resides in the ocean than the atmosphere. Consequently, exchange of CO2 between the ocean and atmosphere is an important control on atmospheric concentrations. During recent ice ages, atmospheric CO2 was naturally 30% lower than pre-industrial levels. Extensive evidence indicates this reduction was caused by greater storage of CO2 in the ocean. During the last glacial interval, changes in ocean circulation, and the resulting changes in ocean chemistry, are widely believed to have played an important role in storing more CO2 in the ocean. However, there is ongoing debate about the specific state of glacial circulation in the Southern Ocean. Previous studies have largely concentrated in the South Atlantic and Southwestern Pacific. There are clearly changes in the chemistry and circulation of water masses between these two regions, but there remains little information from the critical region of the Southern Indian Ocean. This is where much of the CO2 exchange occurs today. Work for this project will focus on cores collected during a recent cruise to Southeast Indian Ocean waters. These cores provide new material from key locations and ocean depths that are needed to fill this knowledge gap. The samples will be analyzed for isotopes of carbon, oxygen, and neodymium to determine water mass and ventilation histories. Initial analyses recently completed by this research group form the foundation for this work that seeks to determine changes in deep ocean circulation and CO2 sequestration. Collaborations with Australian and British scientists is an integral part of this work as these cores are expected to be an important resource for scientists around the world. This work will also support undergraduate and graduate students, and postdoctoral researchers.The circulation and ventilation of water masses at intermediate depths (~500-1400 m) in the Southern Indian Ocean are central to CO2 partitioning between the atmosphere and ocean. During glaciations, changes in both thermohaline circulation and wind-driven Southern Ocean ventilation are believed to have played important roles in sequestering atmospheric CO2. A detailed understanding of the interaction between the physical mechanisms of thermohaline overturning circulation and wind-driven ventilation requires precise definition of changes in water mass boundaries and properties across the deglaciation. The use of vertical and horizontal transects of sediment core material has been fundamental in identifying past variations in the structure of the ocean. Published transects of paleo-proxies in the glacial South Atlantic differ substantially from the Southwest Pacific, suggesting that processes in the Southeast Indian Ocean had a significant influence on glacial CO2 exchange. Consequently, this proposed work will focus on a selected suite of six cores obtained on the CROCCA-2S cruise in 2018 (Coring to Reconstruct Ocean Circulation and Carbon-dioxide Across 2 Seas). These 6 cores have been selected to create depth and latitudinal transects underlying both subantarctic and subtropical waters in the Southeast Indian Ocean from a region west and south of Australia. Our 18O stratigraphies suggest continuous sedimentation and coherent glacial-interglacial signals between these core sites. Efforts will concentrate on constraining surface frontal locations that shift in response to changes in atmospheric circulation, as well as deep water mass boundaries and properties that vary with changes in meridional overturning circulation patterns. The ultimate scientific objective is to determine the temporal evolution of the horizontal and vertical distribution of proxies that will be used to reconstruct water sources (e.g. 18O and Nd isotopes) and the ventilation history (e.g.13C) in this critical region of the Southern Ocean.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.

如今，海洋中的二氧化碳含量是大气中的五十倍。因此，海洋和大气之间的二氧化碳交换是对大气浓度的重要控制。在最近的冰河时期，大气中的二氧化碳含量自然比工业化前水平低 30%。大量证据表明，这种减少是由于海洋中二氧化碳储存量增加造成的。人们普遍认为，在最后一个冰期期间，海洋环流的变化以及由此产生的海洋化学变化在海洋中储存更多二氧化碳方面发挥了重要作用。然而，关于南大洋冰川环流的具体状态一直存在争论。此前的研究主要集中在南大西洋和西南太平洋。这两个区域之间的水团化学和循环存在明显变化，但南印度洋关键区域的信息很少。这是当今大部分二氧化碳交换发生的地方。该项目的工作重点是在最近前往东南印度洋水域的航行中收集的岩芯。这些岩心提供了填补这一知识空白所需的来自关键地点和海洋深度的新材料。将分析样品的碳、氧和钕同位素，以确定水质量和通风历史。该研究小组最近完成的初步分析为这项旨在确定深海环流和二氧化碳封存变化的工作奠定了基础。与澳大利亚和英国科学家的合作是这项工作不可或缺的一部分，因为这些核心预计将成为世界各地科学家的重要资源。这项工作还将为本科生、研究生以及博士后研究人员提供支持。南印度洋中等深度（~500-1400 m）水团的循环和通风是大气和海洋之间二氧化碳分配的核心。在冰川作用期间，温盐环流和风驱动的南大洋通风的变化被认为在封存大气二氧化碳方面发挥了重要作用。要详细了解温盐翻转环流和风驱动通风的物理机制之间的相互作用，需要精确定义冰消过程中水体边界和特性的变化。 使用沉积物芯材的垂直和水平横断面对于识别过去海洋结构的变化至关重要。已发表的南大西洋冰川古代理断面与西南太平洋有很大不同，这表明东南印度洋的过程对冰川二氧化碳交换具有重大影响。因此，这项拟议工作将重点关注 2018 年 CROCCA-2S 巡航中获得的一组选定的六个核心（取芯以重建跨 2 个海域的海洋环流和二氧化碳）。选择这 6 个核心来创建澳大利亚西部和南部地区东南印度洋亚南极和亚热带水域下方的深度和纬度横断面。我们的 18O 地层表明这些核心地点之间有连续的沉积作用和连贯的冰期-间冰期信号。工作重点将集中于约束随大气环流变化而变化的地表锋面位置，以及随经向翻转环流模式变化而变化的深水团边界和特性。最终的科学目标是确定代理的水平和垂直分布的时间演变，这些代理将用于重建南大洋这一关键区域的水源（例如 18O 和 Nd 同位素）和通风历史（例如 13C）。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。