Generation of internal waves by ocean tides

海洋潮汐产生内波

• 批准号: 2113639
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2113639
• 关键词: Generation; internal; waves; ocean; tides

ides are the oceanic response to well-known gravitational forcing by the Sun and Moon. These hugely energetic oscillations influence various parts of the Earth system, such as the history of the lunar orbit, the transport of heat by the large-scale ocean circulation, and ice sheets flowing into the polar oceans.As tidal currents flow over the bottom topography of the ocean, they generate internal gravity waves of tidal frequency in the density-stratified ocean interior. Although almost invisible from the ocean surface, these internal tides play an important role in a range of coastal and open-ocean dynamics. Of particular interest is the amount of energy converted from the (surface) tide to internal tides (along with the magnitude of the implied internal tide drag on the depth-averaged flow), and how this energy is transported within the ocean interior.In this PhD project, simple mathematical models of internal tide generation and propagation will be developed in idealised three-dimensional geometries, building on previous two-dimensional studies. This involves making some combination of simplifying assumptions about the motion (e.g., linear, weakly nonlinear, time-periodic), density stratification (e.g., uniform, piecewise constant), and sea-floor topography (e.g., small-amplitude, stepped), so that the nonlinear partial differential equations of motion can be reduced to a more tractable system. Solutions can then be sought analytically or via simple numerical computations, allowing a wide range of parameter space to be explored. This gives a better understanding of the energy transfer from (surface) tides to internal tides in different forcing scenarios, which is known to have a non-trivial dependence upon topographic width and height.A particular focus would be on extending the solutions and methods of [7], which accounted for arbitrarily large topographic variations but only in two dimensions, to three-dimensional settings. The main targets are to1. Understand internal tides generated by a three-dimensional surface tide (in particular, the Kelvin wave) above a two-dimensional topography (representing a continental slope). The Kelvin wave is the dominant form of the surface tide in many coastal zones, and the implied energy transfers are significant on a global scale.2. Understand the role of topographic undulations in the along-shore direction, i.e., for a three-dimensional tide above a fully three-dimensional topography. It is known from observations that canyons (for exam-ple) lead to enhanced internal tide generation (and dissipation).

IDE是对众所周知的引力强迫的海洋反应。这些巨大的振荡影响了地球系统的各个部分，例如月球轨道的历史，大规模海洋循环的热量运输以及流入极地海洋的冰片。由于潮流流过海洋的底部地形，它们会产生潮汐频率的潮汐频率，在密度的海洋间隙中。尽管从海洋表面几乎看不见，但这些内部潮汐在一系列沿海和开放海洋动力学中起着重要作用。特别感兴趣的是从（表面）潮汐转化为内部潮汐的能量量（以及暗示的内部潮汐在深度平均流量上的拖累的大小），以及如何在海洋内部运输这种能量。在这个博士学位项目中，简单的潮汐生成和传播的简单数学模型将在理想化的三维层次上建立以前的两种构建，并在以前的两二维研究中开发。这涉及将简化的假设组合到有关运动（例如线性，弱的非线性，时间周期性），密度分层（例如，均匀，分段常数）和海底地形（例如，小振幅，步进），以使非线性部分差分平等的运动系统的运动系统更加偏低的系统。然后可以通过分析或通过简单的数值计算来寻求解决方案，从而可以探索广泛的参数空间。这可以更好地了解不同强迫场景中从（表面）潮汐到内部潮汐的能量转移，这是对地形宽度和高度的非平凡依赖性。特别的重点是扩展[7]的解决方案和方法[7]，该方法涉及任意较大的地形变化，但仅在两个维度中，到三维设置。主要目标是TO1。理解由二维地形（代表大陆斜率）上方的三维表面潮汐（尤其是开尔文波）产生的内部潮汐。开尔文波是许多沿海地区表面潮汐的主要形式，在全球范围内隐含的能量转移很重要。2。了解地形起伏在沿岸方向上的作用，即，对于完全三维地形上方的三维潮汐。从观察结果中知道，峡谷（为了进行检查）会导致内部潮汐产生（和耗散）增强。