Nontraditional baroclinic wave effects in the Strait of Gibraltar

一般波浪理论认为，斜压波是由海底地形上的正压潮产生的，并从产生源传播，分解成一个等级有序的内波包系统。然而，马拉加大学在直布罗陀海峡中部及海峡以外（距阿尔博兰海海峡50公里）的系泊处进行的为期三个月的测量中收集的大部分观测数据并不支持这一观点。不到40%的注册波包显示出秩有序结构，而其余的波包明显是非秩有序的。波浪过程的最新认识与观测证据之间的明显矛盾是当前研究的一个巨大挑战和强大动力。重要的是要牢记由潮汐产生的内波发起的混合过程对海峡和邻近地区的区域生态状况以及对全球范围内地中海深水的形成所起的巨大作用。在该项目中假设，观察到的包的不规则结构是沿通道大振幅内波与其横向边界传播的更一般的相互作用机制的表现，在横向边界发生了广泛的破波，水混合，波折射和反射。这些过程在每个波包中重复多次，产生了复杂的空间波结构，其中波能可以从波转换到波并沉入湍流。因此，本研究旨在填补对海峡内大振幅波三维演化机制尚未研究的空白。与以往许多理论研究利用二维思想或流体静力近似计算压力，排除非流体静力内混的影响不同，本项目旨在应用三维全非线性非流体静力数值模型，并结合观测数据来描述和量化与大振幅内波传播有关的海峡动力学过程。实现项目目标的基础是使用在直布罗陀海峡收集的详细观测数据集和应用麻省理工学院最先进的一般环流模式。

General wave theory suggests that baroclinic bores produced by a barotropic tide over bottom topography and propagated from the source of generation, disintegrate into a system of well rank-ordered internal waves packet. However, the majority of observational data collected in the Strait of Gibraltar by the University of Malaga during the three-month measurements at moorings located in the middle of the strait and beyond it (50 km off the strait in the Alboran Sea) doesn't support this idea. Less than 40% of all registered wave packets demonstrated the rank-ordered structure, whereas the rest of wave packets were clearly non-rank ordered. An evident contradiction between the up-to-date understanding of the wave process and observational evidence is a big challenge and strong motivation of the present study. It is important to make clear bearing in mind the great role which mixing processes initiated by tidally generated internal waves play both for regional ecological situation in the strait and adjacent areas and for the formation of the Deep Mediterranean Waters on a global scale. It is hypothesized in the project that the irregular structure of the observed packets is a manifestation of a more general mechanism of interaction of propagating along the channel large-amplitude internal waves with its lateral boundaries where extensive wave breaking, water mixing, wave refraction and reflection take place. Being repeated many times in every wave packet, these processes produce a complex spatial wave structure in which wave energy can transform both from wave to wave and sink to turbulence. Thus, the present proposal is intended to fill the gap in understanding of the not studied yet mechanism of the three-dimensional evolution of large-amplitude internal waves in the strait. As distinct from many previous theoretical studies which exploited the two-dimensional idea or the hydrostatic approximation for pressure and excluded the effects related to non-hydrostatic internal mixing, this project is aimed to apply a three-dimensiona fully-nonlinear nonhydrostatic numerical model and in combination with observational data to describe and quantify dynamical processes in the strait related to propagation of large amplitude internal waves. The achievement of the project goals is based on the the use of detailed observational data set collected in the Strait of Gibraltar and application of the state-of-the art the Massachusetts Institute of Technology general circulation model.