Collaborative Research: Causes and Effects of Shelf-Edge Internal Tide Variability

将使用四维数值模拟和诊断方法研究大陆坡附近内潮的产生和传播。 其目的是解释观测到的内潮变化和它们产生的非线性波。 该研究将集中于世界各地普遍存在的亚临界潮汐流（流速小于波速）产生的长波长线性内波（内潮）。 三个内部潮汐效应将被检查：变量生成，非均匀传播，并转换为非线性波形。 将使用麻省理工学院的多学科模拟、估计和同化系统（MSEAS）进行一系列模拟，其中大部分是通过与数据比较在中尺度上调整的流体静力原始方程模型。 模型配置的范围将从理想化的测深、分层和流动条件到通过数据驱动建模获得的现实条件。 收集的结果的相互比较将揭示可变四维内部潮汐产生和传播的物理学，目的是描述该过程如何发生在真实的海洋中。 新的MSEAS非流体静力学模式将用于研究非线性转换过程。 通过与遥感数据和一个月的现场观测数据的对比，验证了该结果对真实的海洋的适用性，从而更好地理解和准确模拟中尺度和亚中尺度特征、表面和内部潮汐、非线性内波的起源以及这些过程的强变率的相互作用。 将评价使用不同数值方案的流体静力和非流体静力原始方程模型，以进行内潮预测。 内潮和非线性内波，以及它们与更大尺度的相互作用，影响着广泛的自然和人为活动。 这些包括生命周期和分布的氧气，营养物质，浮游生物，鱼类和其他掠食者，海军的业务和监视，水下声学，和模式的diapycnal混合和水体发展在夏季的强烈分层。 此外，这些波浪是剪切、强底流和水在阳光和黑暗之间循环的主要来源。 它们是混合过程的能量来源，而混合过程对底栖生境、浮游生物和鱼类的生命周期以及营养物和污染物的分布都很重要。 所有结果，包括模型输出，将分发给海洋研究人员和社区。 一名沿海海洋学学生将接受教育，一名博士后研究员将接受进一步指导。

Internal tide generation and propagation near continental slopes will be studied using a four-dimensional numerical simulation and diagnosis approach. The purpose is to explain observed variability in internal tides and the nonlinear waves they spawn. The study will concentrate on long wavelength linear internal waves (internal tides) generated from sub-critical tidal flow (current speed less than wave speed), ubiquitous around the world. Three internal tide effects will be examined: variable generation, heterogeneous propagation, and conversion to nonlinear waveform. A set of simulations will be performed with the MIT Multidisciplinary Simulation, Estimation, and Assimilation System (MSEAS), mostly with the hydrostatic primitive equation model already tuned at mesoscales via comparison with data. Modeled configurations will range from idealized bathymetric, stratification, and flow conditions to realistic conditions obtained via data-driven modeling. Inter-comparisons of the collected results will divulge the physics of variable four-dimensional internal tide generation and propagation, with the intent of describing how the process occurs in the real ocean. The new MSEAS non-hydrostatic model will then be used to study nonlinear conversion processes. Applicability of the results to the real ocean will be verified via comparison to remote sensing and in situ data from a one-month long experiment.This work will lead to better understanding and accurate modeling of interactions of mesoscale and sub-mesoscale features, surface and internal tides, origins of nonlinear internal waves, and strong variability of these processes. Hydrostatic and non-hydrostatic primitive equation models using different numerical schemes will be evaluated for internal tide predictions. Internal tides and nonlinear internal waves, and their interactions with larger scales, impact a wide range of natural and man-made activities. These include life cycles and distributions of oxygen, nutrients, plankton, fish, and other predators, naval operations and surveillance, underwater acoustics, and patterns of diapycnal mixing and water mass development in the summer season of strong stratification. In addition, these waves are a major source of shear, strong bottom currents, and cycling of water between sunlight and darkness. They are energy sources for mixing processes which are important to benthic habitat, plankton and fish life cycles, and distributions of nutrients and contaminants. All results, including model outputs, will be disseminated to ocean researchers and communities. A coastal oceanography student will be educated and a post-doctoral fellow further instructed.