Near-Surface Conversions of Semi-Diurnal Internal Tide Beam Energy

当重力作用下的潮汐流过地形时，它们会扰乱海洋的内部分层（例如，在冷水上的温暖层），产生内部振荡（内部潮汐），具有相对较强的电流和较短的空间尺度。内潮的能量在深海混合方面起着重要作用，随后对温度、盐度和营养物分布产生影响，对海洋动力学和海洋地球化学，包括气候-时间尺度的变化产生深远的影响。因此，内潮中能量的分布是一个相当重要的课题。该项目的重点是阐明内部潮汐能如何以及有多少到达深海。调查人员将进行一系列数值调查，以描述和量化向上传播的半日内潮与海洋表面附近的可变分层相互作用并向下反射时发生的过程。首要的问题是“有多少能量是'失去'从内部潮汐在其过境和反射？“尽管海洋上层内部潮汐能量的这种损失很少受到关注，但它可能导致海洋混合可用的能量显著减少，这对于维持深度分层以及为表面附近的初级生产提供营养物质至关重要。由于海洋和气候数值模式对混合分布的敏感性，这些过程在海洋和气候数值模式中的适当表示仍然是一个深入研究的课题。.一位研究生Sherry Chou女士，她为这个项目的提案提供了大量的材料，她将继续她在内波科学和数值模拟技术方面的培训，并将完成她的论文。数值模拟的结果也将告知如何最好地应用海洋仪器来研究复杂的内波过程在未来。该项目的主要目标如下：（1）确定从内潮到其他现象的能量通量的范围（例如，孤波次谐波;超谐波），因为它在不同的环境条件下与上层海洋分层和自由表面相互作用（如不同的小尺度和大尺度分层结构）;以及（2）从数值研究中探索如何最好地尝试区分和量化不同的现象，这些现象可能在内潮通过真实的海洋期间同时出现，鉴于海洋学仪器在空间和时间上的取样限制，

As the gravitationally-forced tides flow over topography they disturb the ocean's internal stratification (e.g., layers of warm over cold water), creating internal oscillations (internal tides) with relatively strong currents and short spatial scales. The energy of the internal tides plays an important role in mixing the deep ocean with subsequent impacts on temperature, salinity and nutrient distributions that have far-reaching consequences for ocean dynamics and biogeochemistry, including climate-time-scale variability. The distribution of the energy in the internal tides is therefore a subject of considerable consequence. This project is focused on elucidating how, and how much, internal tide energy reaches the deep ocean. The investigators will undertake a set of numerical investigations to characterize and quantify the processes occurring when an upward-propagating, semi-diurnal, internal tide interacts with the variable stratification near the surface of the ocean and reflects back downward. The overarching question is "how much energy is 'lost' from the internal tide during its transits and reflection?"Even though this loss of internal tide energy in the upper ocean has received little attention, it may result in a significant reduction in the amount of energy available to ocean mixing, which is critical for maintaining the stratification at depth, as well as the supply of nutrients for primary production near the surface. Proper representation of such processes in oceanic and climate numerical models continues to be a subject of intense research due to the sensitivity of these models to mixing distributions. . A graduate student, Ms. Sherry Chou, who has provided much material for the proposal resulting in this project, will continue her training in internal wave science and numerical modeling techniques, and will complete her dissertation. The numerical modeling results will also inform how best to apply oceanographic instrumentation to study intricate internal wave processes in the future. The project's principal objectives are as follows: (1) To ascertain the range of the fluxes of energy from the internal tide into other phenomena (e.g., solitary waves; sub-harmonic waves; super-harmonic waves) as it interacts with the upper ocean stratification and free surface under different environmental conditions (such as different small-scale and large-scale stratification structures); and, (2) To explore from the numerical investigations how best to try to discriminate and quantify the different phenomena, which may all be present at once during the internal tide's transit through the real ocean, given the spatial and temporal sampling limitations of oceanographic instrumentation.