Collaborative Research: Tracing Pacific Ocean circulation and ventilation during the warm Pliocene Epoch

合作研究：追踪上新世温暖时期的太平洋环流和通风

• 批准号: 2225829
• 负责人: Mariano Remírez
• 金额: $ 63.61万
• 依托单位: George Mason University
• 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: 2023-01-15 至 2025-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2225829&HistoricalAwards=false
• 关键词: Collaborative; Research; Tracing; Pacific; Ocean

A large portion of human-induced carbon dioxide emissions, and the heat that they trap within Earth’s climate system, are being absorbed by the global ocean. The long-term impacts of this absorption on climate and ocean circulation are poorly understood. Forecasts of 21st-century climate change suggest that global warming will lead to a more stratified ocean and weaker global ocean circulation, which would have major ramifications for regional and global climate. However, recent studies suggest that ocean circulation was stronger, not more sluggish, during warm intervals earlier in Earth’s history. This potential discrepancy warrants a better characterization of ocean conditions during warmer-than-present climates of the past. To do so, the study will focus on intervals in the geologic past during which atmospheric carbon dioxide concentrations were similar to today, and temperatures were several degrees warmer. The most recent geologic interval that meets this criterion is the Pliocene Epoch (5.33 to 2.58 million years ago). The primary goal of this project is to generate paleoceanographic records to test models suggesting that there was a strong overturning circulation in the North Pacific Ocean during the Pliocene Epoch. This award will support the careers and training of five early-career scientists, and train and mentor high school and undergraduate students.The goals of this proposal are to: 1) test the recent hypothesis that there was North Pacific deep-water formation and an active Pacific Meridional Overturning Circulation present at times during the warm Pliocene; 2) trace the regional distribution of ocean ventilation; and 3) refine the use of redox, temperature, and productivity proxies in bulk sediments and foraminifera for reconstructing Pliocene North Pacific Ocean ventilation, nutrient availability, and water mixing. A multi-proxy approach will examine intermediate to deep ocean circulation patterns across two key geologic intervals: the mid-Pliocene warm period through the intensification of Northern Hemisphere glaciation (~2.5 to 3.3 Ma) and the early Pliocene (~4.9 to 5.1 Ma). This project will generate new records of i) redox and productivity proxies from bulk sediments, ii) redox, productivity, and water mass mixing proxies from benthic foraminifera, and iii) productivity and temperature proxies from planktic foraminifera, at four sites (IODP 882, 883, 887, and 1208) that cover a range of depths and locations across the North Pacific Ocean. In parallel, the study will analyze a series of coupled climate model simulations with active biogeochemical and d13C cycling. The model tracer, circulation, isotope, and ventilation age results will aid in the interpretation of the newly generated data. This multi-proxy approach, underpinned by climate model analysis, will help ensure the feasibility of the proxy-inferred dynamics.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.

全球海洋吸收了大部分人类诱导的二氧化碳排放量以及它们在地球气候系统中的热量。这种吸收对气候和海洋循环的长期影响知之甚少。对21世纪气候变化的预测表明，全球变暖将导致更加分层的海洋和较弱的全球海洋循环，这将对地区和全球气候产生重大影响。但是，最近的研究表明，在地球历史早期温暖的间隔内，海洋循环更强壮，更迟钝。这种潜在的差异值得在过去的温暖气候中更好地表征海洋状况。为此，这项研究将集中在地质过去的间隔上，在此期间，大气中的二氧化碳浓度与今天相似，温度温暖了几度。符合该标准的最新地质间隔是上新世时期（5.33至258万年前）。该项目的主要目的是生成古虫学记录，以测试模型，这表明在上新世时期，北太平洋的循环中有很强的循环。该奖项将支持五名早期职业科学家的职业和培训，并培训和指导高中和本科生。该提议的目标是：1）测试最近在温暖新世时期存在的北太平洋深水形成和活跃的太平洋子午线倒闭的循环； 2）追踪海洋通风的区域分布； 3）完善在散装沉积物和有孔虫中使用氧化还原，温度和生产力代理，以重建上新近北太平洋通风，营养供应和水混合。多种方法将在两个关键的地质间隔内检查中间至深海循环模式：中新世的温暖时期，通过北半球冰川的强化（〜2.5至3.3 Ma）和早期的上新世（〜4.9至5.1 mA）。该项目将产生i）氧化还原和生产力的新记录，ii）来自底栖有孔虫的氧化还原，生产力和水量混合代理，以及iii）浮游物有孔虫的生产力和温度代理，在四个地点，在四个地点（IODP 882，882，883，883，887，887和1208），范围遍布该范围和范围。同时，该研究将分析具有活性生物地球化学和D13C循环的一系列耦合气候模型模拟。模型示踪剂，循环，同位素和通风年龄结果将有助于解释新生成的数据。这种受气候模型分析为基础的多种方法的方法将有助于确保代理依据的动态的可行性。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子优点和更广泛的影响来审查标准，认为通过评估来获得支持。