Internal Waves in the General Oceanic Circulation

内波在海洋的体积中传播，受到密度变化和地球自转的影响。当它们破裂时，它们混合在一起，从寒冷的深渊中将水向上移动，并从沐浴在阳光下的表面上加热。当受到风的强迫时，内波在上层海洋非常活跃，参与直接的大气-海洋交换，并可能从包含大部分海洋动能的大尺度涡旋中提取能量。这些涡旋被称为地转涡旋，其特征是压力梯度和科里奥利力之间的平衡。我建议研究内波如何在大空间尺度（100公里到全球）和长时间尺度（数月到数百年）上影响海洋环流。我和我的小组将主要使用分析和数值工具，并将这个项目分为三个主要方向。第一个方向是关于内部潮汐，即以潮汐频率振荡的波浪。我们将研究它们如何产生或破坏势涡，势涡是最能描述地转涡旋的量。我们还将研究相反的情况：内部潮汐是如何被地转涡旋折射的，以及这种不稳定的潮汐折射如何影响SWOT的测量，SWOT是未来的美法卫星高度计，加拿大也为该高度计做出了贡献。第二个方向将研究地转流在流过波纹底时如何将能量转化为内波，以及这些内波最终如何耗散这些能量。我们的假设是，内波与深层水力跳跃（可以描述为水下瀑布）相互作用，以增强深层破裂、消散和混合。我们将在二维和三维数值模拟中研究这种现象。研究的第三个方向将是研究内波与小尺度地转流之间的相互作用，如海洋表面附近的小涡旋或海洋锋。我们将研究在锋面中传播的波如何破裂以及它们如何从锋面中提取能量。我们还将进行理论研究，以了解调节内波和小尺度地转流之间相互作用的守恒定律。这项工作可能会阐明SWOT观察到的过程。

Internal waves propagate in the volume of the ocean, and are influenced by density variations, as well as the Earth's rotation. When they break, they mix and move water up from the cold abyss, and heat down from the sun-bathed surface. When forced by wind, internal waves are very active in the upper ocean, participate in direct atmosphere-ocean exchanges, and might extract energy out of the large-scale vortices that contain the majority of the ocean's kinetic energy. These vortices are called geostrophic and are characterized by a balance between pressure gradients and the Coriolis force. ***I propose to study how internal waves influence the oceanic circulation over large spatial scales (100 km to global) and long time scales (months to centuries). My group and I will mostly use analytical and numerical tools and organise this program into three main directions. The first direction is about internal tides, namely waves, that oscillate at tidal frequencies. We will investigate how they create or destroy potential vorticity, which is the quantity that best describes geostrophic vortices. We will also study the opposite situation: how internal tides are refracted by geostrophic vortices, and how this unsteady refraction of the tide could affect measurement made by SWOT, the future USA-French satellite altimeter to which Canada also contributes. The second direction will investigate how geostrophic flows lose energy to internal waves when they flow against the corrugated bottom, and how these internal waves eventually dissipate this energy. Our hypothesis is that internal waves interact with deep hydraulic jumps (which could be described as underwater waterfalls) to enhance deep breaking, dissipation and mixing. We will study this phenomenon in two- and three-dimensional numerical simulations. The third direction of research will be to study the interactions between internal waves and small-scale geostrophic flows, such as small vortices or oceanic fronts near the surface of the ocean. We will study how waves propagating in fronts break and how they extract energy out of fronts. We will also undertake a theoretical study to understand the conservation laws that regulate interactions between internal waves and small-scale geostrophic flows. This work might shed light on processes, observable by SWOT.