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: 2225830
• 负责人: Jordan Abell
• 金额: $ 54.48万
• 依托单位: University of Arizona
• 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=2225830&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.

人类引起的二氧化碳排放及其在地球气候系统中吸收的大部分热量正在被全球海洋吸收。人们对这种吸收对气候和海洋环流的长期影响知之甚少。本世纪的气候变化表明，全球变暖将导致海洋更加分层和全球海洋环流减弱，这将对区域和全球气候产生重大影响。然而，最近的研究表明，在温暖时期，海洋环流更强，而不是更缓慢。这种潜在的差异需要更好地描述过去比现在气候温暖的时期的海洋条件。为此，该研究将重点关注过去地质时期大气二氧化碳浓度与现在相似的时期。今天，温度升高了几度，符合这一标准的最近地质区间是上新世（5.33 至 258 万年前）。该项目的主要目标是生成古海洋记录。测试上新世期间北太平洋存在强烈翻转环流的模型。该奖项将支持五位早期职业科学家的职业生涯和培训，并培训和指导高中生和本科生。该奖项的目标建议：1）检验最近的假设，即在温暖的上新世期间有时存在北太平洋深水形成和活跃的太平洋经向翻转环流；2）追踪海洋通风的区域分布；3）完善使用；大量沉积物和有孔虫中的氧化还原、温度和生产力代理，用于重建上新世北太平洋通风、营养物可用性和水混合。多代理方法将检查两个关键地质区间的中到深海洋环流模式：中-深海洋环流模式。通过北半球冰川作用（约 2.5 至 3.3 Ma）和上新世早期（约 4.9 至 5.1 Ma）的强化，本项目将产生上新世温暖期。四个地点的 i) 散装沉积物的氧化还原和生产力指标，ii) 底栖有孔虫的氧化还原、生产力和水体混合指标，以及 iii) 浮游有孔虫的生产力和温度指标的新记录（IODP 882、883、887、和1208）覆盖了北太平洋的一系列深度和位置。同时，该研究将分析一系列气候耦合模型。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，这种以气候模型分析为基础的多代理方法将有助于确保该模型的可行性。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。