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

半日内潮汐束能量的近地表转换

• 批准号: 1538427
• 负责人: Douglas Luther
• 金额: $ 37.99万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1538427&HistoricalAwards=false
• 关键词: Near; Surface; Conversions; Semi; Diurnal

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.

当重力驱动的潮汐流过地形时，它们会扰乱海洋的内部分层（例如，冷水上的温暖层），从而产生具有相对较强的洋流和较短的空间尺度的内部振荡（内部潮汐）。内潮汐的能量在混合深海以及随后对温度、盐度和营养物分布的影响方面发挥着重要作用，这些影响对海洋动力学和生物地球化学（包括气候时间尺度的变化）产生深远的影响。因此，内潮汐中的能量分布是一个具有相当大影响的主题。该项目的重点是阐明内潮汐能量如何以及有多少到达深海。研究人员将进行一系列数值研究，以描述和量化向上传播的半日内潮汐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。最重要的问题是“内潮汐在传输和反射过程中‘损失’了多少能量？”尽管上层海洋内潮汐能量的损失很少受到关注，但它可能会导致海洋混合可用的能量显着减少，而海洋混合对于维持深度分层以及为近地表初级生产提供营养物质至关重要。由于这些模型对混合分布的敏感性，在海洋和气候数值模型中正确表示此类过程仍然是深入研究的主题。 。研究生 Sherry Chou 女士为该项目的提案提供了大量材料，她将继续接受内波科学和数值建模技术的培训，并将完成她的论文。数值模拟结果还将告知如何最好地应用海洋仪器来研究未来复杂的内波过程。该项目的主要目标如下： (1) 确定不同环境条件（如不同的小尺度和大尺度层结结构）下内潮与上层海洋层结和自由表面相互作用时从内潮到其他现象（如孤立波、次谐波、超谐波）的能量通量范围； (2) 考虑到海洋学仪器的空间和时间采样限制，从数值研究中探索如何最好地区分和量化在内潮穿过真实海洋期间可能同时出现的不同现象。