Quantifying biological, diagenetic and global redox effects on uranium “stable” isotopes in deep-sea corals across glacial-interglacial cycles

量化冰期-间冰期循环中深海珊瑚中铀“稳定”同位素的生物、成岩和全球氧化还原效应

基本信息

批准号：
2054892
负责人：
Francois Tissot
金额：
$ 48.23万
依托单位：
California Institute of Technology
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054892&HistoricalAwards=false
关键词：
Quantifying biological diagenetic global redox

项目摘要

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Most life in the ocean requires an adequate supply of dissolved oxygen. The oxygen concentration of seawater is impacted by temperature, ocean circulation, and biological activity. All of these factors may change in response to rising atmospheric carbon dioxide levels. Geologic records of ocean oxygen concentration can show how changing climate has influenced marine oxygen concentrations in the past. That knowledge will improve predictions of ocean oxygen levels in the future. Natural glacial cycles are linked to changes in atmospheric carbon dioxide concentrations. This study will reconstruct marine oxygen levels across the last glacial cycle. The study will estimate dissolved oxygen using a new method - records of natural uranium isotopes preserved in deep-sea corals. These corals record the composition of seawater at the time of their growth. The study will analyze fossil corals spanning the last more than 200,000 years. These records will improve understanding of the links between climate and ocean oxygen levels. The Broader Impacts of the project include support for a postdoctoral researcher and a graduate student. The research team will work with the Caltech Center for Teaching, Learning & Outreach to arrange education and outreach activities. Those activities include visits to K-12 schools, mentoring of high-school summer research projects, and hosting of public lectures. The goal of these activities is to increase public awareness of past and current climate change. To understand how ocean oxygen levels have fluctuated during glacial-interglacial cycles, this work will apply a new U isotope (238U/235U) paleo-redox proxy to a unique collection of deep-sea corals. Uranium is a redox-sensitive element whose isotopic composition in the ocean (i) is predominantly controlled by the global extent of seafloor anoxia, and (ii) can be faithfully recorded in carbonates when they are devoid of diagenetic and detrital influences. The deep-sea corals to be studied here grew in oxygenated environments on seamounts in the open ocean, meaning that local and/or secondary processes are unlikely to have impacted their U isotopic composition. By characterizing, at high temporal resolution, the 238U/235U of these exceptionally well-preserved deep-sea corals from multiple sites and depths over the last approximately 200,000 years, a detailed seawater 238U/235U record will be reconstructed. To resolve even subtle variations in 238U/235U, state-of-the-art methods achieving precision and accuracy of ±0.01-0.03‰ on 238U/235U data will be employed. To most robustly interpret the high-resolution and high-precision record to be acquired, a novel inverse isotope mass balance model will be used, which will allow quantification of the extent of seafloor anoxia across glacial-interglacial cycles.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.

该奖项是根据2021年《美国救援计划法》（公法117-2）全部或部分资助的。海洋中的大多数寿命都需要足够的溶解氧。海水的氧浓度受到温度，海洋循环和生物学活性的影响。所有这些因素可能会随着大气二氧化碳水平上升而变化。海洋氧气浓度的地质记录可以表明气候变化如何影响海洋氧浓度。这些知识将在未来改善海洋氧气水平的预测。天然冰川周期与大气二氧化碳浓度的变化有关。这项研究将在最后一个冰川周期重建海洋氧气水平。这项研究将使用一种新方法估算溶解的氧 - 深海珊瑚中保存的天然铀同位素的记录。这些珊瑚在生长时记录了海水的组成。该研究将分析过去超过20万年的化石珊瑚。这些记录将提高人们对气候和海洋氧气之间的联系的理解。该项目的更广泛影响包括支持博士后研究人员和研究生。研究团队将与加州理工学院的教学，学习和宣传中心合作，进行安排教育和外展活动。这些活动包括访问K-12学校，高中夏季研究项目的心理以及举办公开讲座。这些活动的目的是提高公众对过去和当前气候变化的认识。为了了解在冰川间冰期循环期间海洋氧水平如何波动，这项工作将应用新的U同位素（238U/235U）古雷克斯代理，以将其用于独特的深海珊瑚集合。铀是一种对氧化还原敏感的元素，其在海洋中的同位素组成主要由海底缺氧的全球范围控制，并且（ii）当它们缺乏成岩成分和有害影响时，可以忠实地记录在碳酸盐中。这里要研究的深海珊瑚在开阔的海洋海山的氧化环境中生长，这意味着局部和/或次要过程不太可能影响其U同位素组成。通过表征，在高度暂时的分辨率下，将在过去大约200,000年中从多个地点和深度提供的这些特殊保存完好的深海珊瑚中的238U/235U进行表征，将重建详细的Seawater 238U/235U记录。为了解决238U/235U的微妙变化，将雇用238U/235U数据的最先进方法±0.01-0.03‰。为了大多数强烈地解释要获得的高分辨率和高精度记录，将使用一种新型的逆同位素质量平衡模型，这将允许量化跨冰川间际循环的海底缺氧程度的量化。这项奖项反映了NSF的法定任务，并通过评估智力效果，并通过评估了Crcriatial and crotial and througial and crotia and crowia and Broadia and througia and crowia and tocria and tocria and tocriatial and tobrit and tocria and tobrit and tocria and tobrit。