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: 1940962
• 负责人: Elisabeth Sikes
• 金额: $ 11.5万
• 依托单位: Rutgers University New Brunswick
• 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 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1940962&HistoricalAwards=false
• 关键词: Collaborative; Research; Determining; climate; related

The modern oceans hold about fifty times more CO2 than the atmosphere, but scientists think this may have been even greater during glacial periods causing a significant reduction in the amount found in the atmosphere. Reduced atmospheric CO2 concentration during ice ages likely contributed to colder global temperatures. Much of the atmospheric-oceanic CO2 exchange takes place in the Southern Ocean and is associated with processes of oceanic and atmospheric circulation. By studying the water mass structure and chemical characteristics, scientists hope to define key controls over the exchange of CO2, namely where water masses rise and sink from the surface and the pathways they travel in the deeper ocean. This study will establish age models and allow detailed correlations between a unique set of sediment cores previously collected from the Indian Ocean. These cores span a range of depths and locations that will support associated efforts of an international team of researchers to study and track important water masses in the area using a variety of chemical tracers found in the sediments deposited as the Earth transitioned out of the last glacial ice age into the modern climate. This work provides undergraduate student research opportunities and supports an early career post-doctoral scientist.The circulation and ventilation of water masses at intermediate depths (~500-1400 m) in the Southern Indian Ocean are central to atmosphere-ocean CO2 partitioning. During glaciations, changes in both thermohaline circulation and wind-driven Southern Ocean ventilation are believed to have played an important role 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, leading to the idea that processes in the Southeast Indian Ocean had a significant influence on glacial CO2 exchange. Consequently, this proposed work will provide foundational stratigraphy in 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. Provisional multi-sensor core logger and CaCO3 data suggest coherent glacial-interglacial stratigraphies between these core sites. Efforts will concentrate on expanding this initial stratigraphy, principally via planktonic and benthic δ18O analyses. Associated efforts will constrain surface frontal locations that shift in response to changes in atmospheric circulation, as well as deep water mass boundaries and properties that vary with ocean circulation patterns. The ultimate scientific objective is to determine the temporal evolution of the horizontal and vertical distribution of proxies (e.g.13C, 18O, Nd isotopes) that will reconstruct the water source and ventilation history of 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.

现代海洋中的二氧化碳含量约为大气的五十倍，但科学家认为，在冰河时期，这一含量可能更高，导致大气中二氧化碳含量显着减少。冰河时期大气中二氧化碳浓度的降低可能导致全球气温下降。大部分大气-海洋二氧化碳交换发生在南大洋，并与海洋和大气环流过程相关。通过研究水团结构和化学特征，科学家希望确定二氧化碳交换的关键控制因素，即水的位置。质量上升和下降这项研究将建立年龄模型，并允许以前从印度洋收集的一组独特的沉积物岩心之间的详细相关性，这些岩心跨越一系列深度和位置，以支持相关的研究。一个国际研究小组的成员致力于利用在地球从最后一个冰川时代过渡到现代气候时沉积的沉积物中发现的各种化学示踪剂来研究和跟踪该地区的重要水团这项工作为本科生提供了研究。机会和支持早期职业生涯博士后科学家。南印度洋中等深度（~500-1400 m）水团的循环和通风是冰川期大气-海洋二氧化碳分配的核心，温盐环流和风驱动的南大洋发生变化。通风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之间的相互作用，需要精确定义整个水体边界和特性的变化。沉积物核心材料的垂直和水平横断面的使用对于识别过去海洋结构的变化至关重要。已发表的古代理断面在冰川期南大西洋与西南太平洋有很大不同，从而得出这样的观点：东南印度洋的过程对冰川二氧化碳交换产生了重大影响，这项拟议的工作将为 2018 年 CROCCA-2S 巡航中获得的一组选定的六个岩心提供基础地层学。 （取芯以重建跨 2 个海洋的海洋环流和二氧化碳）这 6 个岩心被选择用于在澳大利亚以西和以南的地区创建东南印度洋亚南极和亚热带水域的深度和纬度横断面。传感器岩心记录仪和碳酸钙数据表明，这些岩心地点之间存在连贯的冰期-间冰期地层。主要工作将集中于扩大这一初始地层。通过浮游和海底 δ18O 分析，相关工作将限制随大气环流变化而变化的表面锋面位置，以及随海洋环流模式变化的深水团边界和特性。最终的科学目标是确定时间演化。代理（例如 13C、18O、Nd 同位素）的水平和垂直分布，将重建南大洋这一关键区域的水源和通风历史。该奖项反映了 NSF 的法定使命通过使用基金会的智力优点和更广泛的影响审查标准进行评估，并被认为值得支持。

项目成果

Neodymium isotope evidence for coupled Southern Ocean circulation and Antarctic climate throughout the last 118,000 years

过去 118,000 年南大洋环流和南极气候耦合的钕同位素证据

• DOI: 10.1016/j.quascirev.2021.106915
• 发表时间: 2021
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Williams, Thomas John;Martin, Ellen E.;Sikes, Elisabeth;Starr, Aidan;Umling, Natalie E.;Glaubke, Ryan
• 通讯作者: Glaubke, Ryan