NSFGEO-NERC: Energy transfer between submesoscale vortices and resonantly-forced inertial motions in the northern Gulf of Mexico

次中尺度流动和近惯性运动是上层海洋普遍存在的特征。最近发展的理论认为，亚中尺度流动和近惯性运动的相互作用在关闭平衡环流和非平衡波的能量收支方面发挥着重要作用。由于在相对可控的环境中观察这两种运动的挑战，这些理论尚未在现场得到充分检验。墨西哥湾北部是一个天然的实验室，非常适合做这项工作。在这里，密西西比-阿查法拉亚河羽流形成了丰富的亚中尺度涡旋和锋面，在夏季由陆地-海风驱动，迫使惯性运动接近共振。拟议的研究将涉及密集的现场运动，利用新的观测技术，将与理想化和现实的数值模拟紧密结合，研究密西西比-阿查法拉亚河羽流中亚中尺度涡旋和近惯性运动的相互作用。其目的将是描述、量化和理解平衡和不平衡运动之间的能量交换，以及由相互作用可能产生的湍流级联。更具体地说，数值和观测实验将被设计用来检验这样的假设：锋面上惯性运动引起的等压线的周期性应变，低位涡度水的俯冲，以及近惯性波与次中尺度涡旋相互作用的传播、捕获和反射，促进了能量交换，并导致整个水柱的混合增强。这个问题主要是在理想化流动形态下从理论上进行研究的，但还没有像本文所建议的那样在受控环境下进行观测探索。这项研究将把观测与亚中尺度分辨率模拟和大涡模拟结合起来，事实证明，这种结合在理解复杂、多尺度观测流动的基本物理方面是有效的。

Submesoscale flows and near-inertial motions are ubiquitous features of the upper ocean. Recently developed theories have posited that the interaction of submesoscale flows and near-inertial motions could play an important role in closing the energy budgets of both the balanced circulation and the unbalanced waves. These theories have yet to be fully tested in the field due to the challenges of observing both types of motions in a relatively controlled setting. The northern Gulf of Mexico is a natural laboratory that is ideal for doing this. Here, the Mississippi-Atchafalaya river plume forms a rich field of submesoscale eddies and fronts, which in the summer are driven by a land-sea breeze that forces inertial motions at near resonance.The proposed research will involve intensive field campaigns utilizing novel observational techniques that will be closely integrated with idealized and realistic numerical simulations to study the interaction of submesoscale eddies and near-inertial motions in the Mississippi-Atchafalaya river plume. The objective will be to characterize, quantify, and understand the energy exchanges between balanced and unbalanced motions and the turbulent cascade that can result from the interaction. More specifically, the numerical and observational experiments will be designed to test the hypotheses that periodic straining of isopycnals by inertial motions in fronts, subduction of low potential vorticity water, and the propagation, trapping, and reflection of near-inertial waves interacting with submesoscale eddies facilitate the energy exchange and result in enhanced mixing throughout the water column.The proposed research tackles one of the outstanding questions in physical oceanography of how the kinetic energy in the balanced circulation is dissipated, in particular through wave-mean flow interactions. This question has been studied mostly theoretically for idealized flow configurations, but it has not been explored observationally in a controlled setting, as proposed here. The research will integrate observations with submesoscale-resolving simulations and large-eddy simulations, a combination that has proven to be effective in understanding the fundamental physics of complex, multi- scale observed flows.