Collaborative Research: A porewater perspective on benthic sources of neodymium to the North Atlantic

合作研究：从孔隙水角度了解北大西洋的底栖钕来源

• 批准号: 2210663
• 负责人: Sophia Hines
• 金额: $ 50.94万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2027-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2210663&HistoricalAwards=false
• 关键词: Collaborative; Research; porewater; perspective; benthic

Documenting deep ocean circulation changes is important to understanding past climate variability. Neodymium (Nd) isotopes, recorded in deep ocean sediments, have been used to reconstruct past ocean circulation. However, several recent studies suggest that some Nd is released into seawater from the underlying sediment, which would complicate the ability to use Nd isotopes to accurately track deep water in the ocean. This project will investigate Nd in seafloor sediments and near bottom water in the Northwest Atlantic. The study region is a location where North Atlantic Deep Water is formed. Broader impacts include mentoring support to allow two early-career scientists to serve as co-chief scientists for the field program. There is also support for high school students from an institution with a high percentage of students that are underrepresented in STEM, and undergraduates from a minority-serving institution.The interpretive framework of Nd isotopes as a paleo circulation proxy relies on deep ocean signals being driven by mixing between water masses with little influence from benthic sources of Nd to the ocean. It also requires that Nd isotopes are recorded accurately in sediments and endmember composition is independently known through time. Recent studies have challenged this framework, suggesting that benthic fluxes from ocean sediments may exert a primary control on deep water isotopic composition. However, the limited global coverage of direct benthic flux measurements (from only 10 published locations primarily in the North Pacific) prevents a complete understanding of the marine Nd cycle. This project will (i) quantify the fluxes of Nd to bottom water from sediments, (ii) examine how those fluxes affect the isotopic composition of North Atlantic Deep Water, (iii) investigate the role of diagenetic reactions in setting pore water rare earth element geochemistry, and (iv) determine what isotopic signals are recorded in marine archives. The field component of this project will occupy sites along two depth transects in the Labrador Sea, and it will involve collecting sediment and pore water from short cores, corresponding filtered bottom water, and deep-sea particles, in order to fully describe the system. The study location will allow for investigation of the role that regional geology and water depth play in setting the benthic flux of Nd to seawater. Altogether, this project will be one of the most thorough investigations to date of the controls on benthic Nd flux, the impact of benthic fluxes on the Nd isotopic composition of North Atlantic Deep Water, the sedimentary environmental conditions that facilitate Nd release, and the impact of these processes on authigenic Nd isotope records.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.

记录深海环流变化对于了解过去的气候变化非常重要。记录在深海沉积物中的钕同位素已被用来重建过去的海洋环流。然而，最近的几项研究表明，一些Nd从底层沉积物中释放到海水中，这将使使用Nd同位素准确跟踪海洋深水的能力变得复杂。该项目将调查西北大西洋海底沉积物和近底层水中的钕。研究区域是北大西洋深水形成的位置。更广泛的影响包括指导支持，使两名早期职业科学家担任该领域计划的联合首席科学家。也有支持高中学生从一个机构的学生比例很高，在STEM中代表性不足，和本科生从少数民族serving institutions.The解释框架的Nd同位素作为古环流代理依赖于深海信号被驱动的混合水团之间的影响很小，从海底来源的Nd海洋。它还要求在沉积物中准确记录Nd同位素，并通过时间独立了解端元组成。最近的研究对这一框架提出了挑战，表明海洋沉积物的底栖通量可能对深水同位素组成产生主要控制作用。然而，有限的全球范围内的直接底栖通量测量（从只有10个公布的地点，主要是在北太平洋）防止海洋钕循环的完整理解。该项目将（i）量化Nd从沉积物到底层水的通量，（ii）研究这些通量如何影响北大西洋深水的同位素组成，（iii）调查成岩反应在确定孔隙水稀土元素地球化学中的作用，以及（iv）确定海洋档案中记录的同位素信号。该项目的实地部分将占据拉布拉多海两个深度剖面的沿着地点，并将涉及从短岩心收集沉积物和孔隙水、相应的过滤后的底层水和深海微粒，以充分描述该系统。研究地点将允许调查的作用，区域地质和水深发挥设置底栖通量的钕海水。总而言之，该项目将是迄今为止对海底Nd通量控制、海底通量对北大西洋深水Nd同位素组成的影响、促进Nd释放的沉积环境条件、以及这些过程对自生Nd同位素记录的影响。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的学术价值和更广泛的影响审查标准。