Collaborative Research: US GEOTRACES PMT: Investigating geochemical tracers of the Pacific nitrogen cycle and budget

合作研究：US GEOTRACES PMT：研究太平洋氮循环和预算的地球化学示踪剂

• 批准号: 1736756
• 负责人: Karen Casciotti
• 金额: $ 42.07万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-01-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736756&HistoricalAwards=false
• 关键词: Collaborative; Research; US; GEOTRACES; PMT

Nitrate is an important nutrient that marine plants and algae need for growth. It is abundant in deep ocean waters, but scarce in most sunlit surface waters. The purpose of this project is to better understand what controls the availability of nitrate in the deep ocean and its delivery to surface waters. Researchers from Stanford University, Princeton University, and Brown University will analyze the stable isotopes of seawater nitrate collected between Alaska and Tahiti in the Pacific Ocean. The data will provide information about the supply of nitrate to a large section of the Pacific Ocean and allow informed decisions on past and future changes in marine photosynthesis. This collaborative project will be carried under the GEOTRACES program, an international effort to understand the distribution of elements in the global ocean. This study will include undergraduate, graduate, and postdoctoral researchers at all three academic instititutions. The investigators will develop a 1-day workshop for the Teachers as Scholars program, for middle and high school teachers at Princeton University. The workshop will focus on accessing and visualizing ocean data sets and other content available on the internet for project-based learning in the classroom. Investigators will also participate in teacher workshops offered each summer at Stanford University. Data from this project will be made available to the public through the Biological and Chemical Oceanography-Data Management Office (www.bco-dmo.org). The data will also be compiled in GEOTRACES data products that will be freely available.The isotopic composition of nitrate in the ocean interior records biogeochemical and physical processes on the time scales of years, decades, centuries, and millennia, with the shallow subsurface and deep ocean recording shorter and longer time scales, respectively. These are meaningful time scales in the efforts to (1) understand the feedbacks that structure the biogeochemistry of N in the ocean, ocean productivity, and the global carbon cycle, (2) reconstruct past changes in ocean biogeochemistry and carbon cycling, and (3) perhaps predict future changes. This proposal seeks to analyze the nitrate isotopes during the upcoming US GEOTRACES Pacific Meridional Transect (GP15) between Alaska and Tahiti. Nitrate isotopes provide critical constraints on the ocean N cycle and budget, especially in the Pacific Ocean where a variety of processes affect the distribution of nitrate and its supply to surface waters. This largely meridional section of nitrate isotope data will be broadly useful as part of the growing nitrate isotope dataset for the global ocean and for comparison to the many complementary geochemical data sets that will be generated as part of this GEOTRACES effort. In addition, nitrate isotopes in aerosols will be measured to support interpretations of nitrate isotopes in surface waters along the section. The proposed measurements will contribute to the investigation of three overarching questions: 1) What are the similarities and differences in N biogeochemistry among the different nutrient-rich regions in the Pacific basin: the Southern Ocean, equatorial Pacific, and subarctic North Pacific, and how do they affect nitrate supply to low-latitude surface waters? 2) What sources of nitrogen fuel export production in surface waters across the Pacific? 3) What are the roles in surface and subsurface processes in the distribution of nitrate isotopes in the ocean interior?

硝酸盐是海洋植物和藻类生长所需的重要营养素。它在深海水域中含量丰富，但在大多数阳光照射的表层水域中却很少。该项目的目的是更好地了解是什么控制着深海硝酸盐的供应及其向地表水域的输送。来自斯坦福大学、普林斯顿大学和布朗大学的研究人员将分析在太平洋阿拉斯加和塔希提岛之间收集的海水硝酸盐的稳定同位素。这些数据将提供有关太平洋大部分地区硝酸盐供应的信息，并有助于就海洋光合作用过去和未来的变化做出明智的决策。该合作项目将在 GEOTRACES 计划下进行，该计划是一项旨在了解全球海洋元素分布的国际努力。这项研究将包括所有三个学术机构的本科生、研究生和博士后研究人员。研究人员将为普林斯顿大学的初中和高中教师举办为期一天的“教师学者计划”研讨会。该研讨会将重点关注访问和可视化海洋数据集以及互联网上提供的其他内容，以便在课堂上进行基于项目的学习。研究人员还将参加斯坦福大学每年夏天举办的教师研讨会。该项目的数据将通过生物和化学海洋学数据管理办公室（www.bco-dmo.org）向公众提供。这些数据还将被编译成免费提供的 GEOTRACES 数据产品。海洋内部硝酸盐的同位素组成记录了数年、数十年、数百年和数千年时间尺度上的生物地球化学和物理过程，浅层地下和深层海洋分别记录较短和较长的时间尺度。这些都是有意义的时间尺度，旨在 (1) 了解构成海洋中氮生物地球化学、海洋生产力和全球碳循环的反馈，(2) 重建海洋生物地球化学和碳循环过去的变化，以及 (3 ）也许可以预测未来的变化。该提案旨在分析即将进行的阿拉斯加和塔希提岛之间的美国 GEOTRACES 太平洋经线横断面 (GP15) 期间的硝酸盐同位素。硝酸盐同位素对海洋氮循环和预算提供了关键限制，特别是在太平洋，那里的各种过程影响硝酸盐的分布及其对地表水的供应。硝酸盐同位素数据的大部分经向部分将作为全球海洋不断增长的硝酸盐同位素数据集的一部分而广泛有用，并可与作为 GEOTRACES 工作的一部分生成的许多补充地球化学数据集进行比较。此外，还将测量气溶胶中的硝酸盐同位素，以支持对该剖面沿线地表水中硝酸盐同位素的解释。拟议的测量将有助于研究三个首要问题：1）太平洋盆地不同营养丰富区域（南大洋、赤道太平洋和亚北极北太平洋）氮生物地球化学有何异同？它们会影响低纬度地表水的硝酸盐供应吗？ 2) 跨太平洋地表水域氮燃料出口生产的来源是什么？ 3）地表和地下过程对海洋内部硝酸盐同位素的分布有何作用？