Collaborative Research: Southeast Pacific and Southern Ocean Seawater Isotopes Determined from US GEOTRACES GP17-OCE and GP17-ANT Samples

合作研究：从美国 GEOTRACES GP17-OCE 和 GP17-ANT 样品中测定东南太平洋和南大洋海水同位素

• 批准号: 2049577
• 负责人: Elisabeth Sikes
• 金额: $ 30.68万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049577&HistoricalAwards=false
• 关键词: Collaborative; Research; Southeast; Pacific; Southern

The stable isotopic composition of the oxygen atom in seawater (d18O) is controlled by evaporation, precipitation, and riverine or glacial meltwater input. Most of the deep interior water masses in the ocean are formed or modified in the Southern Ocean and sink to fill the deep layers that circulate throughout the world’s oceans. The d18O signatures in seawater can be used as tracers for these sub-surface water masses once they sink to depth. The Southern Ocean and South Pacific are critical locations for water mass formation and thus, for understanding global overturning circulation, carbon cycling and climate dynamics. However, data on the d18O of seawater, particularly in the sub-surface, is virtually nonexistent for the South Pacific and Southern Ocean. Moreover, our understanding of past temperature and oceanic processes based on the d18O signature in marine carbonates (e.g. corals and foraminifera) have relied on the assumption that variations in the oxygen isotopic composition of the sub-surface water masses are nominal through time, which can be directly tested on a wider basis using new technologies during this project. Investigators will conduct analyses of seawater d18O from samples collected from depth transects during the US GEOTRACES science expedition to the South Pacific (GP17-OCE) and the Amundsen Sea sector of the Antarctic continental margin (GP17-ANT). This ocean region is of particular significance because it is experiencing rapid environmental changes in the past few decades, including the fastest melting of ice shelves around the entire Antarctic. This project will support the development of diverse involvement in teaching and outreach efforts in a primarily undergraduate and Hispanic serving institution. The outreach activities will provide ample opportunities to engage students from underrepresented groups in both formal and informal settings. It is well-established from first principles that d18O and d2H of seawater have a positive relationship to salinity, but regional variations in the isotopic relationship of seawater to salinity are poorly constrained. Temperature reconstructions relying on d18O in calcite microfossils biologically precipitated in equilibrium with seawater and preserved in marine sediments are only quantitative if the seawater d18O (d18Osw) in which that carbonate was precipitated is known. Despite the reliance of these paleo-estimations on the d18O of modern seawater, surface measurements are few and far between and sub-surface data in the South Pacific and Southern Oceans is even more limited. Filling this fundamental gap in data to quantify the influence of precipitation, evaporation and glacial melt water on the d18O and d2H of interior seawater masses is globally relevant to our understanding of ocean circulation and broader climate dynamics. The development and improvement of new laser-based spectroscopy techniques such as off-axis integrated cavity output spectroscopy (OA-ICOS) and cavity ring-down spectroscopy, allows for seawater d18O and d2H analyses to be run quickly and cost effectively compared to traditional IRMS (Isotope Ratio Mass Spectrometry). A core aim of this project is to compare and contrast IRMS and OA-ICOS analyses to address accuracy, precision and offsets between methods. Obtaining d18Osw directly contributes to the GP17-OCE stated aims of characterizing near- and far-field trace element and isotope (TEI) inputs and to the GP17-ANT stated aims of quantifying gradients in TEI distributions and characterizing, glacial meltwater inputs in the Amundsen Sea and Southern Ocean.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.

海水中氧原子（D18O）的稳定同位素组成由蒸发，降水和河流或冰川融合水的输入控制。海洋中的大多数深层内部水块都是在南大洋中形成或修饰的，并下沉，以填充在世界海洋中循环的深层。一旦下沉到深度，海水中的D18O签名就可以用作这些地下水块的示踪剂。南大洋和南太平洋是水质量形成的关键位置，因此，了解全球倾覆循环，碳循环和气候动态。但是，对于南太平洋和南大洋几乎不存在有关海水D18O的数据，尤其是在地面上。此外，我们基于海洋碳酸盐（例如珊瑚和有孔虫）中D18O签名的过去温度和海洋过程的理解放松了以下假设：氧气同位素水质量的氧同位素组成的变化是标称整个时间的标称，可以在本项目的过程中使用更广泛的基础进行新的技术直接测试。研究人员将对从深度样本中的样品进行海水D18O进行分析，从美国地理学科学探险到南太平洋（GP17-OCE）和南极连续边缘（GP17-ANT）的Amundsen Sea Sea区。这个海洋地区特别重要，因为它在过去几十年中正在经历迅速的环境变化，包括整个南极周围冰架最快的融化。该项目将支持潜水员参与初级本科和西班牙裔服务机构的教学和外展工作的发展。外展活动将提供足够的机会，使来自代表性不足团体的学生在正式和非正式环境中。从第一原则中，海水的D18O和D2H与盐度建立了正相关，但是海水与盐度的同位素关系的区域变化受到很大的约束。仅当海水D18O（D18OSW）中，该碳酸盐含量是珍贵的，依赖于海水平衡并保存在海水中并保存在海水中并保存在海水中并保存在海水中并保存在海水中的温度重建。尽管这些古估计在现代海水的D18O上得到了缓解，但在南太平洋和南部海洋中，地面测量很少，而且在南太平洋的地下数据更加有限。在数据中填补了这一基本差距，以量化降水，经济和辉煌的熔体水对内部海水肿块的D18O和D2H的影响，与我们对海洋循环和更广泛的气候动态的理解有关。基于激光的新光谱技术的开发和改进，例如离轴集成腔输出光谱（OA-ICOS）和腔降低响射光谱，允许与传统IRMS（同位素IRMS相比）进行海水D18O和D2H分析。该项目的核心目的是比较和对比IRM和OA-ICOS分析，以解决方法之间的准确性，精度和偏移。 Obtaining d18Osw directly contributes to the GP17-OCE stated aims of characterizing near- and far-field trace element and isotope (TEI) inputs and to the GP17-ANT stated aims of quantifying gradients in TEI distributions and characterizing, glacial meltwater inputs in the Amundsen Sea and Southern Ocean.This award reflects NSF's statutory mission and has been deemed precious of support through使用基金会的智力优点和更广泛的影响评估标准进行评估。