Collaborative Research: Study of Convectively-Breaking Internal Solitary Waves of Depression: High Accuracy/Resolution Modeling and Observational Data Analysis

内孤立波（ISWs）是一种普遍存在的海洋现象，存在于大陆斜坡和大陆架、海底峡谷以及海洋地形特征上。它们可以在保持形状的同时长距离携带能量，是向上层海洋提供营养物质的有效提供者，并可以通过在公海和沿海水域之间交换热量、盐、营养物质和水团来影响初级生产和海洋生态。例如，最近对新泽西州大陆架内孤立波浅滩的测量表明，与内部剪切不稳定有关的波负责横跨斜斜的总热通量的50%，并驱动水平粒子在几公里内的输运，从而对大陆架能量学和生态学起着至关重要的作用。由于内部存在大量的倾覆，对流破裂isw的湍流扩散系数和颗粒输运预计比剪切不稳定isw大100倍。由于这些不稳定性的瞬态性质和仪器的限制，现有的对流不稳定isw的原位观测在解决相关湍流方面受到限制。该项目将能够可靠地确定浅滩isw的对流（和剪切）不稳定性的机制和首选位置。对流断裂的含义将通过量化相关的湍流通量和粒子输运作为参数空间的函数来解决。对于对流破裂isw是否是大多数富含高振幅波的环境的一个至关重要的特征，一个更可靠的评估将是可能的。在发生的首选位置、潜在物理、湍流通量和陆上颗粒输送方面，对浅滩性isw对流破裂过程的更好理解和量化，将有助于在更大规模模型中可靠地参数化这些过程。ISW破裂和由此产生的湍流（集中在大陆斜坡和大陆架上的现象）的参数化可能与通常用于公海内部潮汐、内部背风波和分层湍流的参数化有根本不同。一名波多黎各人、少数族裔的博士生将接受分层海洋物理学和高性能计算方面的培训。这项研究的结果将被整合到康奈尔大学环境流体力学的相关课程中，以及伊萨卡高中和华盛顿大学空间资助暑期本科生研究项目应用物理实验室正在进行的推广工作中。分析代码、后处理结果和精选的原始数据将通过专门的在线数据库提供给更广泛的社区。该项目将研究内部孤立波（ISWs）在缓慢倾斜的现实（和理想）水深上的破碎，主要是由于对流（但也有剪切）不稳定。高精度/分辨率大涡模拟（LES）将与南海大陆斜坡上对流破裂isw的广泛数据集分析相结合。先前对这些观测结果的分析表明，对流不稳定的大振幅ISWs内部有再循环的湍流核心，与100米级的倾覆和强化的消散和混合有关，大约是公海的1000倍。导致对流不稳定和相关湍流混合的机制尚不清楚。二维模拟将首先研究对流不稳定性导致ISW破裂的机制和首选位置（作为底部坡度、初始波陡度和背景斜压潮流的函数）。以对流破裂为重点，一系列计算/数据密集型并行三维LES，配备拉格朗日粒子跟踪，将提供破碎过程的增强时空分辨率，并将量化所产生的湍流通量和波尺度水平能量通量对上述参数的依赖。除了为LES提供水深和分层/电流强迫外，现有的SCS观测结果及其进一步分析将作为一致性检查和探索LES与现场数据之间参数空间共同趋势的基础。拉格朗日浮子的实际和模型数据分析将检验和量化对流破碎isw（即具有循环核心的波）对粒子的夹带、输运和沉降。湍流通量和耗散率的拉格朗日替代估计将使相关的涡扩散率的计算成为可能。这些结果将决定isw驱动的湍流如何与弱波-波相互作用和分层湍流以及它们之间的过渡有关。

Internal solitary waves (ISWs) are ubiquitous oceanic phenomena found on continental slopes and shelves, in submarine canyons, and over oceanic topographic features. They can carry energy over long distances while maintaining their shapes, are efficient suppliers of nutrients into the upper ocean, and can impact primary production and marine ecology through the exchange of heat, salt, nutrient, and water masses between the open ocean and coastal waters. For example, recent measurements of internal solitary waves shoaling on the continental shelf of New Jersey indicate that waves linked to shear instability in their interior are responsible for 50% of the total heat flux across the pycnocline and drive horizontal particle transport over a few kilometers, thereby exerting a critically important role for the shelf energetics and ecology. On account of the massive overturns in their interior, the turbulent diffusivities and particulate transport in convectively-breaking ISWs are expected to be as much as a hundred times larger than those in shear-unstable ISWs. Existing in-situ observations of convectively unstable ISWs are limited in their resolution of the associated turbulence due to the transient nature of these instabilities and instrument limitations. This project will enable the robust determination of the mechanisms and preferred locations of convective (and shear) instability of shoaling ISWs. The implications of convective breaking will be addressed through quantifying the associated turbulent fluxes and particle transport as a function of parameter space. A more reliable assessment of whether convectively-breaking ISWs are a critically important feature of most environments rich in high-amplitude waves will be possible. The improved understanding and quantification of the convective breaking process in shoaling ISWs, in terms of preferred locations of occurrence, underlying physics, turbulent fluxes and onshore particulate transport, will facilitate the reliable parameterization of such processes in larger-scale models. The parameterizations of ISW breaking and resulting turbulence, phenomena focused on the continental slope and shelf, might be fundamentally different from those typically used for internal tides, internal lee waves and stratified turbulence in the open ocean. One Ph.D. student, a native of Puerto Rico and member of a under-represented minority, will be trained in stratified ocean physics and high performance computing. The findings of this study will be integrated in relevant coursework in Environmental Fluid Mechanics at Cornell and in on-going outreach efforts at Ithaca High School and the Applied Physics Laboratory at the University of Washington's Space Grant Summer Undergraduate Research Program. Analysis codes, post-processed results and select raw data will be made available to the broader community through a dedicated online database.This project will investigate the breaking, due to primarily convective (but also shear) instability, of internal solitary waves (ISWs) shoaling over gently sloping realistic (and idealized) bathymetries. High-accuracy/resolution Large Eddy Simulations (LES) will be integrated with analysis of an extensive dataset of convectively breaking ISWs over the continental slope in the South China Sea. Previous analysis of these observations has revealed convectively unstable, large-amplitude ISWs with recirculating turbulent cores in their interior associated with order 100 meter overturns and intensified dissipation and mixing, roughly a thousand times greater than in the open ocean. The mechanisms leading to the convective instability and the associated turbulence mixing remain unknown. Two-dimensional simulations will first investigate the mechanisms and preferred locations of ISW breaking due to convective instability as a function of bottom slope, initial wave steepness and background baroclinic tidal current. Focusing on convective breaking, a range of computation/data intensive parallel three-dimensional LES, equipped with Lagrangian particle tracking, will then provide enhanced spatiotemporal resolution of the breaking process and will quantify the dependence of the resulting turbulent fluxes and wave-scale horizontal energy fluxes on the above parameters. Beyond providing bathymetric and stratification/current forcing to the LES, the existing SCS observations, and further analysis thereof, will serve as a basis for consistency checks and exploration of common trends in parameter space between LES and field data. Analysis of data from, actual and model, Lagrangian floats will examine and quantify particle entrainment, transport and detrainment by convectively-breaking ISWs, namely waves with recirculating cores. Alternative Lagrangian estimates of turbulent fluxes and dissipation rates will enable the computation of associated eddy diffusivities. These results will determine how ISW-driven turbulence relates to the regimes of weak wave-wave interaction and stratified turbulence and the transition between them.