MOMS: a Minimal Ocean Mixing System

尽管发生在厘米和更小的尺度上，但海洋中的湍流分层混合影响了盆地尺度的环流。许多工作都致力于理解如何用局部湍流参数来表示过程的效率。然而，最近的研究表明，分层混合的物理学不能从它发生的更大背景中抽象出来。在这个项目中，实验室实验将在一个足够大并适当施加压力的水箱中进行，以便它可以更真实地接近在海洋中观察到的条件，这是一个最小的海洋混合系统(MOMS)。实验室测量将提供一种方法来测试在计算机模型中表示混合的理论和实践方法。类似环境中的分层湍流混合也存在于大气中，因此这项研究将在大气科学中产生溢出效应。目前的测量和数值模拟还将构成一个新的数据集，可用作人工智能算法、降阶模型和数据同化技术的训练集，这些技术需要大量的流动知识才能进行验证。最后，利用本研究减少不可逆混合的不确定性将提高大气环流模式在气候尺度上的预测能力。PI将尽一切努力广泛宣传博士后职位，以便接触到传统上被边缘化的候选人。PI还将与SCIREN的当地分会合作，SCIREN是一个将STEM研究人员与当地教师联系起来，以提高年轻人的质量和科学素养的组织。显然，最近调查的工作表明，重点从纯粹的分层混合的局部表征(例如，寻求基于浮力雷诺数的混合效率的参数化)转变为将混合视为动力的最终产物，这种动力始于更大的规模，(潜在)比先前认识的更相互交织。在实验上，这需要重新思考分层混合的问题，以包括一种更自然的方式来强迫问题，以及一个足够大的域，以容纳光谱的各向异性和各向同性部分，即MOMS。因此，在这些实验和数值模拟中收集的数据集将构成一种新的方法来检验和验证理论论点，以模拟横跨各向异性/各向同性分水岭的分层湍流中的能量交换。此外，这项研究旨在提供垂直/水平拖曳仪器与平面/体积分辨率测量之间的联系。该项目还打算在近海条件之间建立联系，将理论和技术挑战结合起来，达到前所未有的规模，北卡罗来纳大学联合流体实验室就是为此而设计的。此外，Craya-Herring框架与结构函数方法相结合，将提供最先进的理论基础来分析湍流的作用，其中间歇性仍然是分析和解释现场测量的关键开放问题，因为在强分层湍流的现场测量中很少观察到混合事件，也很少静态收敛。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。

Despite occurring on centimeter and smaller scales, turbulent stratified mixing in the ocean affects the circulation at basin scales. Much work has been devoted to understanding how to express the efficiency of the process in terms of local turbulent parameters. Recent work though suggests that the physics of stratified mixing cannot be abstracted from the larger context in which it occurs. In this project, laboratory experiments will be conducted in a tank large enough, and suitably forced, that it may approximate more faithfully the conditions observed in the ocean, a Minimal Ocean Mixing System (MOMS). The laboratory measurements will provide a way to test theoretical and practical ways to represent mixing in computer models. Stratified turbulent mixing in a similar environment is also present in the atmosphere, and this research will therefore have a spill-over effect in atmospheric sciences. The present measurements and numerical simulations will also constitute a new dataset which can be used as a training set for Artificial Intelligence algorithms reduced order models and data-assimilation techniques which require a substantial knowledge of the flow for their validation. Finally, reducing uncertainties of irreversible mixing using the present research will improve the predictive power of general circulation models at climate scales. The PI will make every effort to advertise the postdoc position broadly so to reach candidates that traditionally have been marginalized. The PI will also work with the local chapter of SCIREN, an organization that connects STEM researchers with local teachers to improve the quality and scientific literacy of youths.It is clear that the recent work surveyed shows a shift in the focus from a purely local characterization of stratified mixing (e.g., the quest for parameterizations of mixing efficiency based on the buoyancy Reynolds number) to a view that sees mixing as the end product of a dynamic that starts at much larger scales and is (potentially) much more intertwined than previously recognized. Experimentally, this requires rethinking the problem of stratified mixing to include a more natural way to force the problem, and a domain sufficiently large to accommodate both the anisotropic and the isotropic part of the spectrum, a MOMS. The dataset collected in these experiments and numerical simulations will therefore, constitute a novel way to test and validate theoretical arguments to model the energy exchanges in stratified turbulent flows across the anisotropic / isotropic divide. In addition, this research aims to provide a link between vertically/horizontally towed instruments and planar / volume-resolved measurements. This project also intends to establish a link between near-ocean conditions combining theoretical with technical challenges at unprecedented scales for which the UNC Joint Fluids lab is designed. In addition, the Craya-Herring framework combined with the structure functions methods will provide the state-of-the-art theoretical foundations to analyze the role of the turbulence where intermittency remains a key open question to analyze and interpret field measurements, since mixing events are rarely observed nor statically converged in field measurements of strongly stratified turbulence.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.