Collaborative Research: Mesoscale Drivers of Oxygen in the Tropical Pacific

热带太平洋拥有丰富的海洋生物多样性和丰富的渔业资源。它也是世界上最缺氧的盆地，拥有世界上最大的氧气最少区(OMZ)。北太平洋和南太平洋热带海洋保护区由赤道富氧水域隔开，为远洋渔业提供了重要的可居住空间，其摄食行为受到氧气水平降至不适宜居住阈值以下的深度的限制。确定控制这一低氧阈值深度的过程对于了解生态系统动态以及预测和管理该区域的渔业十分重要。该项目的主要目标是了解区域物理过程在确定赤道太平洋氧的三维结构及其在季节和年际时间尺度上的变化方面的作用。研究人员将使用计算机模型和现有观测相结合的方法来描述区域环流模式在维持太平洋海洋保护区的体积和含氧量方面所起的作用。这些模型包括全球海洋环流模型和控制海洋大气圈的生物和化学过程，以及侧重于海洋环流的区域尺度特征(如旋涡)并由观测提供信息的模型。海洋氧循环综合了物理、生物和化学现象，使其成为将下一代科学标准(NGSS)应用到K-12课堂的理想课程主题。在这个项目中，调查人员将与来自当地学区的NGSS早期实施者密切合作，将该项目的研究问题、知识以及相关数据和可视化工具引入教学计划，使学生和教师直接接触到科学过程。一个主要的认识缺口涉及到赤道洋流系统(ECS)和热带不稳定涡旋(TIV)在OMZ通风中的作用，以及这些通风途径的氧气供应在多大程度上被它们对养分运输、生产力和呼吸速率的影响所补偿，引发了以下问题：1.赤道洋流系统及其与中尺度涡旋的相互作用如何调节OMZ的边界和通风？2.是什么决定了该地区OMZ通风的季节和年际变化？3.TIV通过什么物理和生物地球化学机制影响赤道太平洋氧？这一建议的一个中心假设是，赤道潜流和TIV介导的通量的横向输送在决定赤道上太平洋平均氧结构和可变性方面起主导作用。这些问题将使用不同配置的一系列模式来研究，包括涡旋分辨率和粗略全球模式、热带太平洋的涡旋分辨率数据同化区域模式和拉格朗日分析。这项工作预计将：1)阐明氧与热带太平洋海洋环流和气候变化的耦合机制；2)在模型中告知OMZ偏差的驱动因素；3)指导观测需求，包括正在进行的热带太平洋观测系统(TPOS 2020)的努力和该地区未来生物地球化学(BGC)ARGO浮标的部署。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The tropical Pacific Ocean is home to rich marine biodiversity and abundant fisheries. It is also the most oxygen-deficient basin in the world, hosting the world’s largest oxygen minimum zones (OMZs). The northern and southern tropical Pacific OMZs are separated by oxygen-rich waters along the equator that provide important habitable space for open ocean fisheries whose feeding behavior is limited by the depth at which oxygen levels decrease below uninhabitable thresholds. Characterizing the processes that control the depth of this low oxygen threshold is important to understanding ecosystem dynamics and to predicting and managing fisheries in this region. The primary goal for this project is to understand the role of regional physical processes in setting the 3-dimensional structure of oxygen in the equatorial Pacific and its changes on seasonal and interannual time scales. The investigators will use a combination of computer models and existing observations to describe the role that regional circulation patterns play in maintaining the volume and oxygen content of the Pacific OMZs. These include global models of ocean circulation and biological and chemical processes controlling the OMZ, as well as models that focus on regional scale features of ocean circulation (such as eddies) and that are informed by observations. The oceanic oxygen cycle integrates physical, biological, and chemical phenomena, making it an ideal curriculum topic for applying Next Generation Science Standards (NGSS) into K-12 classrooms. In this project, the investigators will work closely with NGSS early implementers from the local school districts to introduce this project’s research questions, knowledge, and relevant data and visualization tools into the lesson plans, exposing students and teachers directly to the scientific process. A major knowledge gap concerns the role of the equatorial current system (ECS) and tropical instability vortices (TIVs) in ventilating the OMZs, and the extent to which oxygen supply by these ventilation pathways is compensated by their effects on nutrient transport, productivity, and respiration rates, motivating the following questions: 1. How does the equatorial current system and its interaction with mesoscale eddies modulate the boundaries and ventilation of the OMZs? 2. What governs the seasonal to interannual variability of OMZ ventilation in this region? 3. Through what physical and biogeochemical mechanisms do TIVs influence equatorial Pacific oxygen? A central hypothesis for this proposal is that lateral transport by the Equatorial Undercurrent and TIV-mediated fluxes play a dominant role in setting the mean oxygen structure and variability of the upper equatorial Pacific. These questions will be examined using a hierarchy of models of various configurations, including an eddy resolving and coarse global model, an eddy resolving data-assimilating regional model of the tropical Pacific, and Lagrangian analysis. The work is expected to i) elucidate the mechanisms coupling oxygen to ocean circulation and climate variability in the tropical Pacific, ii) inform drivers of OMZ biases in models, and iii) guide observing needs including the on-going Tropical Pacific Observing System (TPOS 2020) efforts and future deployments of biogeochemical (BGC) Argo floats in this region.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.