Collaborative Research: Global eddy-driven transport estimated from in situ Lagrangian observations

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。本项目将研究全球海洋中尺度长周期连贯涡旋的流体输送，包括涡旋核内的体积、涡旋外围的瞬时被困流体以及涡旋影响下的环境水团的搅拌效应。该项目将依赖于一种新的涡流识别分析技术（由pi在之前的工作中开发），该技术应用于全球表面漂浮物数据集和声学跟踪的水下浮子历史集的现场测量。这与网格卫星产品中涡流检测的通常方法不同，而是依赖于信号处理技术对浮动轨迹数据的适应。先前基于这种网格产品的研究大大低估了涡流的数量，高估了涡流的大小和被困在其中的水的输送。数据分析将辅以理论、理想和现实的数值模拟。这项工作将解决观察到的无处不在的连贯涡流实际上在它们对大规模流动的影响方面所完成的工作。这是一个具有社会重要性的问题，因为它与发展精确的亚网格尺度参数化一般环流模式有关。该项目将推进拉格朗日数据可行使用的边界，从而为社区提供涡流检测的新工具。该项目将为基础和高级海洋学数据分析的免费在线课程提供支持和信息，以便下一代研究人员能够广泛地使用这些最先进的方法。该项目支持一名早期职业拉丁裔科学家，他将开发与该项目相关的本科教学模块。本项目将以现场拉格朗日观测的重要涡流探测为起点，对相干涡流在驱动流体输运中的作用进行明确的研究。这种检测方法称为涡信号提取，它从拉格朗日轨迹中恢复时变振荡信号分量，而不要求振荡是严格周期性的。可用的数据包括大约24,000个全球地表漂移轨迹，以及另外3,000个来自历史上一组涡流解析浮标的地下轨迹，这两个数据集都是NOAA的数据集。数据分析将辅以理想化和超高分辨率的现实建模。这些组件将用于探索从拉格朗日角度观察涡流场的微妙之处，检查涡流检测方法的理论性质，并研究感兴趣的传输过程的动力学。该项目将分三个部分进行：(i)直接和间接涡旋驱动运输的动力学，（ii）涡旋可观测性问题，以及（iii）全球估计。预期的产品将是通过统计建模对相干涡流特性、种群和边界的新的全球估计，这些统计建模是通过对长期和短暂捕获物理的改进理解而获得的。该项目将进一步提供一个校准过程，通过该过程，遥感特征可以更准确地映射到流体结构上，而水文分析将把面积运输估计转化为质量运输。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This project will examine fluid transport by long-lived coherent mesoscale eddies in the global ocean, including volumes within their coherent cores, transiently trapped fluids in eddy peripheries, and stirring effects in the ambient watermasses due to eddy influence therein. The project would rely on a novel eddy-identifying analysis technique (developed in prior work by the PIs) applied to in-situ measurements from global surface drifter dataset and the historical set of acoustically-tracked subsurface floats. This is a departure from the usual approach of eddy detection in gridded satellite products, relying instead on the adaptation of signal processing techniques to float trajectory data. Prior studies based on such gridded products significantly underestimate numbers of eddies, and overestimate eddy sizes and transport of water trapped within them. Data analysis will be supplemented by theoretical idealized and realistic numerical modeling. This work will address what observed ubiquitous coherent eddies actually accomplish in terms of their effect on the large-scale flow. This is a question of societal importance because of its relevance for the development of accurate subgrid-scale parameterizations for general circulation models. The project will advance the boundaries of the viable use of Lagrangian data, and thus provide new tools for eddy examination to the community. The project will support and inform free online courses in fundamental and advanced oceanographic data analysis, so that that these state-of-the-art methodologies will be broadly accessible to the next generation of researchers. The project supports an early career latino scientist, who will develop an undergraduate-level teaching module related to this project.This project will produce a definitive study on the role of coherent eddies in driving fluid transport, taking significant eddy detections from in situ Lagrangian observations as the starting point. The detection method, called vortex signal extraction, recovers time-varying oscillatory signal components from Lagrangian trajectories, without a requirement for the oscillations to be strictly periodic. Available data include approximately 24,000 global surface drifter trajectories plus another 3,000 subsurface trajectories from an historical set of eddy-resolving floats, both NOAA datasets. Data analysis will be complemented by idealized and ultra-high-resolution realistic modeling. These components will be used to explore the subtleties of observing the eddy field from the Lagrangian perspective, to examine the theoretical properties of the eddy detection methods, and to investigate the dynamics of the transport processes of interest. The project will proceed in three branches: (i) dynamics of direct and indirect eddy-driven transport, (ii) the vortex observability problem, and (iii) global estimates. Anticipated products will be new global estimates of coherent eddy properties, populations, and boundaries through statistical modeling informed by an improved understanding of the physics of long-term and transitory trapping. The project will further provide a calibration process by which remotely-sensed features can be more accurately mapped onto fluid structures, and a hydrographic analysis will convert areal transport estimates into mass transports.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.