Uranium isotopes and past changes in Southern Ocean circulation

铀同位素和南大洋环流过去的变化

• 批准号: 1658445
• 负责人: Christopher Hayes
• 金额: $ 23.95万
• 依托单位: University of Southern Mississippi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658445&HistoricalAwards=false
• 关键词: Uranium; isotopes; past; changes; Southern

Ocean circulation has deep connections with processes around the Earth including the melting or growing of continental ice sheets. The exact mechanisms linking ocean circulation to ice sheet variability can be difficult to tease out using modern observations alone. Geologists therefore look to the past for examples of when ocean circulation changed and how those changes relate to other phenomena in past eras. In particular, it has been found that the circulation of Antarctic Bottom Water, dense water that sinks around the Antarctic continent and fills the deepest parts of the world?'s ocean, may have a very intimate link with melting of the West Antarctic Ice Sheet. The concentration of naturally-occurring uranium in Southern Ocean sediments, formed under low oxygen conditions, is a key tool that has been applied to reconstruct past circulation changes during one past warm period, ~125,000 years ago, in one area of the Southern Ocean. This project will apply this recently developed method to other areas of the Southern Ocean and to other time periods in the past (up to 500,000 years ago) in order to investigate a more robust mechanism for how circulation around Antarctica is linked to ice sheet melting and how this might change in the future. The project supports an early-career researcher as well the training of a graduate and undergraduate students in the research. Outreach will be accomplished through the development of a new course and with high school students through events such as the Ocean Sciences Bowl competition. The project will contribute to infrastructure by developing a new proxy for paleoceanography, which has the potential to better constrain models of ice sheet melting and inform on issues related to climate change and sea level rise.To more accurately reconstruct past deep Southern Ocean oxygenation conditions, and therefore Antarctic Bottom Water (AABW) circulation, the project will utilize a novel geochemical approach using the isotope composition of authigenic uranium (U-234/U-238), augmented by other redox sensitive metals (Re and Mn). This combination of measurements allows for periods of changing oxidation to be identified that elemental proxies alone could not detect. This approach will be applied in multiple Southern Ocean cores to test for reproducibility and sensitivity to varying sedimentary environments. Furthermore, the project will investigate multiple interglacial periods over the past 500,000 years to examine the response of AABW across a range of forcings and Antarctic Ice sheet extents. The result will be a robust perspective on AABW variability during interglacial periods and its relationship to external forcings (orbital configuration, CO2, Southern Ocean productivity) and West Antarctic Ice Sheet melting.

海洋循环与地球周围的过程有着深厚的联系，包括大陆冰盖的融化或生长。将海洋循环与冰盖变异性联系起来的确切机制可能很难仅使用现代观察结果来取消。因此，地质学家将过去介绍了何时改变海洋循环以及这些变化与过去时代的其他现象的关系。特别是，已经发现，南极底水的循环，在南极大陆周围下沉的密集水，填充了世界上最深的海洋，可能与西南极冰盖的融化有着非常紧密的联系。在低氧气条件下形成的南海洋沉积物中自然出现的铀的浓度是一种关键工具，用于在过去一个温暖的时期（约125，000年前）在南大洋的一个地区重建过去的循环变化。 该项目将把这种最近开发的方法应用于南大洋的其他领域以及过去（长达500，000年前）的其他时期，以调查一种更强大的机制，以解决南极周围的循环与冰盖融化以及未来可能如何改变。 该项目支持早期研究人员以及研究研究生和本科生的培训。 外展将通过开发新课程和高中生通过诸如海洋科学碗比赛等活动来实现。 The project will contribute to infrastructure by developing a new proxy for paleoceanography, which has the potential to better constrain models of ice sheet melting and inform on issues related to climate change and sea level rise.To more accurately reconstruct past deep Southern Ocean oxygenation conditions, and therefore Antarctic Bottom Water (AABW) circulation, the project will utilize a novel geochemical approach using the isotope composition of authigenic uranium （U-234/U-238），由其他氧化还原敏感金属（RE和MN）增强。这种测量的组合允许确定仅元素代理无法检测到改变氧化的时期。这种方法将在多个南方海洋核心中应用，以测试对不同沉积环境的可重复性和敏感性。此外，该项目将在过去500，000年内研究多个冰间时期，以检查AABW在一系列强迫和南极冰盖范围内的响应。结果将是对冰间期间AABW变异性的强大视角，及其与外部强迫（轨道构型，CO2，南洋生产力）和南极冰盖融化的关系。

项目成果

Changes in Antarctic Bottom Water Formation During Interglacial Periods

间冰期南极底层水形成的变化

• DOI: 10.1029/2020pa003867
• 发表时间: 2020
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Glasscock, S. K.;Hayes, C. T.;Redmond, N.;Rohde, E.
• 通讯作者: Rohde, E.

Southern Ocean Oxygenation Changes Inferred From Redox‐Sensitive Trace Metals Across Marine Isotope Stage 11

根据海洋同位素第 11 阶段的氧化还原敏感痕量金属推断南大洋氧合变化

• DOI: 10.1029/2021gc009921
• 发表时间: 2021
• 期刊: Geosystems
• 作者: Rohde, E. E.;Hayes, C. T.;Redmond, N.;Glasscock, S. K.
• 通讯作者: Glasscock, S. K.

Global Ocean Sediment Composition and Burial Flux in the Deep Sea

• DOI: 10.1029/2020gb006769
• 发表时间: 2021-04-01
• 期刊: GLOBAL BIOGEOCHEMICAL CYCLES
• 影响因子: 5.2
• 作者: Hayes, Christopher T.;Costa, Kassandra M.;Zhang, Jing
• 通讯作者: Zhang, Jing