Eddy-internal wave interactions in regions of frontogenesis

近惯性波、中尺度涡旋和锋面在海洋中无处不在。经典理论预测，快速、不平衡的波浪和缓慢、平衡的涡流之间的相互作用通常很弱。然而，一项新的理论表明，这种相互作用在锋生区域可能很强，在那里，中尺度应变驱动着横跨锋面的非地转环流，并迅速增强热风切变。地转流的这种变化改变了存在的近惯性波的偏振关系，使它们的水平速度成直线，并导致雷诺应力，从涡流中汲取动能。涡旋传递的动能最终损失到非地转环流中，因此近惯性波在失去平衡中起到了催化作用。在这个过程中，海浪失去了所有的能量。基于一个简单的相互作用理论模型的尺度论证表明，它可以在关闭全球近惯性波和涡旋的动能收支方面发挥重要作用。然而，为了正确地评估这一过程对全球能量平衡的影响，必须理解这一机制的物理学，而不是在空间均匀的锋面和波场模型中使用的简化假设。该项目旨在通过对空间局部化锋面和波场进行一系列流体静力和非流体静力数值模拟来实现这一点。将进行二维模拟，旨在研究波浪的修改，并隔离波浪对平均流的影响。然而，这些将不允许平均流的变化对波动动力学进行反馈。没有这种约束的三维静力模拟将被用来研究这些反馈，并量化波浪对涡动动能的调节。高分辨率的非静力模拟将研究从波动和涡旋场损失的动能到可能的小尺度湍流的最终命运。智力价值：作为拟议研究的基础的理论融合了锋面动力学、内波物理和波平均流相互作用的研究，产生了丰富的新现象，可能有助于揭示地球物理流体动力学中动能如何从平衡运动转移到不平衡运动和消散的基本问题之一。同时，这项工作为近惯性波场中动能的去除提供了一种机制，这是一个尚未完全理解的问题。广泛的影响：拟议的研究解决了物理海洋学中的一个突出问题？中尺度动能是如何消散的。这一点很重要，因为涡旋失去动能的方式会影响它们的性质，从而影响大范围的环流，从而影响气候。这项研究指出了一种途径，在这种途径中，来自涡旋和内波的动能驱动锋面的混合，这对营养通量、初级生产力和水团转化具有影响。这项研究的见解将指导用于全球环流模式的涡旋和近惯性波消散的参数化的发展。该项目将用于培训一名研究生，并包括对一名博士后研究员的指导。研究成果将被纳入引起人们对海洋环流的兴趣和兴趣的讲座和推广活动中。

Near-inertial waves, mesoscale eddies, and fronts are ubiquitous in the ocean. Classical theory predicts that the interaction between the fast, unbalanced waves and the slow, balanced eddies is usually weak. A new theory demonstrates, however, that this interaction can be strong in regions of frontogenesis, where mesoscale strain drives a cross-front ageostrophic circulation and rapidly intensifies thermal wind shear. This change in geostrophic flow modifies the polarization relation of near-inertial waves that are present, making their horizontal velocity rectilinear, and resulting in a Reynolds stress that draws kinetic energy from the eddies. The kinetic energy transferred from eddies is ultimately lost to the ageostrophic circulation, hence the near-inertial waves play a catalytic role in loss-of-balance. In the process the waves lose all of their energy. Scaling arguments based on a simple theoretical model for the interaction suggest that it could play a significant role in closing the global kinetic energy budgets for both near-inertial waves and eddies. To correctly assess the impact of this process on global energy balances, however, the physics of the mechanism must be understood without the simplifying assumption used in the model of a spatially homogeneous front and wave field. This project aims to do this using a hierarchy of hydrostatic and non-hydrostatic numerical simulations of spatially localized fronts and wave fields. Two dimensional simulations will be performed that are designed to study the modifications of the waves and isolate the wave-induced changes to the mean flow. These will not, however, allow the changes in mean flow to feedback on the wave dynamics. Three-dimensional hydrostatic simulations without this constraint will be used to investigate these feedbacks and quantify the wave-induced adjustments to the eddy kinetic energy. The ultimate fate of the kinetic energy lost from the wave and eddy fields to presumably small-scale turbulence will be investigated with high-resolution non-hydrostatic simulations.Intellectual Merit: The theory that forms the basis of the proposed research merges studies of frontal dynamics, internal wave physics, and wave mean flow interactions, yielding rich new phenomena that may shed light on one of the fundamental problems in geophysical fluid dynamics of how kinetic energy is transferred from balanced to unbalanced motions and dissipated. At the same time, the work provides a mechanism for the removal of the kinetic energy in the near-inertial wave field, a problem that is not fully understood.Broader Impacts: The proposed research tackles one of the outstanding questions in physical oceanography ? how the kinetic energy in the mesoscale is dissipated. This is important because how eddies lose their kinetic energy affects their properties, with consequences for the large-scale circulation and hence climate. The research points to a pathway where kinetic energy from eddies and internal waves drives mixing at fronts, with implications for nutrient fluxes, primary productivity, and water mass transformation. Insights from this study will guide the development of parameterizations for the dissipation of eddies and near-inertial waves for use in global circulation models. The project will be used to train a graduate student and includes mentoring of a postdoctoral researcher. The research results will be incorporated into lectures and outreach activities that provoke interest and fascination in the ocean circulation.