A high-density, high-precision zonal section of nitrate isotopes across the South Indian Ocean

南印度洋高密度、高精度硝酸盐同位素纬向剖面

基本信息

批准号：
1851430
负责人：
Daniel Sigman
金额：
$ 29.65万
依托单位：
Princeton University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-10-01 至 2024-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1851430&HistoricalAwards=false
关键词：
density precision zonal section nitrate

项目摘要

The ocean covers most of the Earth's surface, and its physical, biological, and chemical processes determine many aspects of Earth's climate and the chemistry of the atmosphere. Biologically available nitrogen (or "fixed N") is an essential nutrient for the microscopic plants (phytoplankton) in the ocean. The supply of fixed N can limit the growth of phytoplankton and the capacity of the ocean to absorb carbon dioxide, the most important greenhouse gas. Following the flow and transformation of fixed N is a powerful approach for understanding how the physics, biology, chemistry interact to determine the biological fertility of the ocean and its storage of carbon dioxide away from the atmosphere. With such an understanding, we may be able to predict how the ocean will change in response to human activities and thus affect the conditions for life in the future. Nitrate (NO3-) is the primary form of fixed N in the ocean, and both its nitrogen (N) and oxygen (O) atoms occur in more than one mass, or "isotope": 14N and 15N for N and 16O and 18O for O. The ratios of these isotopes are affected by biological processes, and so isotopic measurements of nitrate reveal processes at work in the ocean that are otherwise hard to disentangle. Moreover, the isotope ratio of N in the ocean through time is recorded in the organic matter of the sediments that accumulate on the seafloor. Thus, the isotopes allow us to reconstruct important features of the past ocean, such as how the sequestration of carbon dioxide by ocean life has changed over past climate changes, which may indicate how this sequestration will change in the future. This project will produce the largest data set so far on the isotopic composition of nitrate in the Indian Ocean. The Indian Ocean is one of the three major basins of the global ocean, the one that has been studied the least, and it may prove to be the best basin for reconstructing past surface ocean conditions because of the abundance of microfossils in its sediments. The measurements of nitrate isotopes generated in this project will serve many purposes. As one example, it will allow for a determination of the circulation path by which nitrate is transferred up from the deep waters to the sunlit surface waters where growing phytoplankton require this nutrient. As a second example, the measurements will help to calibrate new nitrogen isotopic methods for reconstructing past ocean conditions, which utilizes the organic matter trapped in the fossil shells of foraminifera, a type of zooplankton. In order to explain these goals and to spread our understanding of the ocean to educators, each of the two years of the project, a 1-day workshop will be held for the Teachers as Scholars program of the Princeton University Program in Teacher Preparation, which brings middle and high school teachers to Princeton to interact with faculty and learn about important scientific questions and research. The workshop will focus on accessing and visualizing ocean data sets and other oceanographic content for active learning in the classroom. Undergraduates will be involved in the research through summer internships, junior projects, and/or senior theses.This project will produce analyses of the nitrate 15N/14N and 18O/16O ratios in samples collected during the upcoming 2019-2020 GO-SHIP I05 zonal section across the South Indian Ocean from South Africa to Australia at 30-33 deg S. Nitrate 15N/14N and 18O/16O provide critical constraints on the cycle and input/output budget of marine fixed N. The I05 nitrate isotope data will be broadly useful, potentially serving as a cornerstone in the global ocean's nitrate isotope data set. Given the lack of nitrate isotope measurements in the Indian Ocean, especially in the main basin away from the low-[O2] regions to the North, this project will fill a major geographic gap. Moreover, it will provide dense spatial and depth coverage with the highest level of precision currently available, allowing for novel hydrography-based calculations of N fluxes. The nitrate isotope samples will be taken from the same bottles from which the GO-SHIP hydrographic and biogeochemical measurements will be made, maximizing the power of the nitrate isotope data set. The data set will be of use to the growing number of numerical ocean model simulations including biogeochemistry, for identifying regional oceanographic processes, and for ground-truthing paleoceanographic tools.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.

海洋覆盖了地球的大部分表面，其物理，生物学和化学过程决定了地球气候的许多方面和大气的化学。生物学上可用的氮（或“固定N”）是海洋中微观植物（浮游植物）的必不可少的营养。固定N的供应可以限制浮游植物的生长以及海洋吸收二氧化碳，最重要的温室气体的能力。遵循固定N的流量和转化是一种强大的方法，用于了解物理，生物学，化学如何相互作用，以确定海洋的生物生育能力及其将二氧化碳储存的储存。有了这样的理解，我们也许能够预测海洋将如何响应人类活动，从而影响未来的生活条件。硝酸盐（NO3-）是海洋中固定n的主要形式，其氮（N）和氧原子（O）原子都以多个质量或“同位素”或“同位素”的形式出现：n和14o和15n的O。解开。此外，通过时间在海洋中的N n同位素比在海底积累的沉积物的有机物中记录。因此，同位素使我们能够重建过去海洋的重要特征，例如，海洋生命二氧化碳的隔离如何在过去的气候变化中发生了变化，这可能表明这种隔离将来会如何变化。该项目将在印度洋的同位素组成上生产最大的数据集。印度洋是全球海洋的三个主要盆地之一，该盆地的研究最少，由于其沉积物中的微化石丰富，它可能被证明是重建过去的表面海洋条件的最佳盆地。该项目中产生的硝酸盐同位素的测量将有许多目的。例如，它将允许确定硝酸盐从深水转移到阳光地表水的循环路径，在那里生长的浮游植物需要这种营养。作为第二个例子，测量结果将有助于校准新的氮同位素方法，以重建过去的海洋条件，该方法利用了被困在有孔虫壳中的有机物（一种浮游动物）。为了解释这些目标并将我们对海洋的理解传播给教育工作者，该项目的两年中的每一个都将为教师举办为期1天的讲习班，作为普林斯顿大学教师准备的学者计划，将中学和高中教师带到普林斯顿，与普林斯顿进行与教师互动，并了解重要的科学问题和研究。研讨会将着重于访问和可视化海洋数据集和其他海洋学内容，以在课堂上积极学习。本科生将通过暑期实习，初级项目和/或高级论点参与研究。该项目将对即将在2019 - 2020年统治的2019 - 2020年GO-SHIP I05领域收集的样品进行硝酸盐分析，并在南非地区的澳大利亚地区，在30-330-30-3 degrate/14 no norrate inter Indration and Inifage of 2019-2020 GO-SHIP I05地区收集的样品中进行分析。海洋固定N的周期和输入/输出预算的约束。I05硝酸盐同位素数据将广泛有用，可能是全球海洋硝酸盐同位素数据集中的基石。鉴于印度洋缺乏硝酸盐同位素测量值，尤其是在北部低位区域的主要盆地中，该项目将填补一个主要的地理差距。此外，它将提供密集的空间和深度覆盖范围，目前可用的最高级别的精度水平，从而可以对N通量进行新的基于水文的计算。硝酸盐同位素样品将取自相同的瓶子，从中可以从中进行船舶水文和生物地球化学测量，从而最大程度地提高硝酸盐同位素数据集的功率。数据集将用于越来越多的数值海洋模型模拟，包括生物地球化学，识别区域海洋学过程，并用于地面流动古海洋学工具。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力和更广泛影响的评估来通过评估来获得支持的。