Nontraditional baroclinic wave effects in the Strait of Gibraltar

一般波动理论认为，正压潮汐在海底地形上产生的斜压钻孔，从产生的源头传播，解体成一个有序的内波包系统。然而，马拉加大学在三个月的时间里在直布罗陀海峡收集的大多数观测数据并不支持这一观点。这些数据是在海峡中部和海峡以外(距离海峡50公里)的系泊处进行的。在所有登记的波包中，只有不到40%的波包显示出排序结构，而其余的波包明显是非排序的。对波浪过程的最新理解与观测证据之间的明显矛盾是本研究的一个巨大挑战和强烈动机。必须铭记由潮汐产生的内波引发的混合过程对海峡及其邻近地区的区域生态状况和全球范围内地中海深层水域的形成所起的巨大作用。该项目假设，观测到的波包的不规则结构是沿航道传播的大幅度内波与其横向边界相互作用的更一般机制的表现，其中发生了广泛的波浪破碎、水混合、波折射和反射。这些过程在每个波包中重复多次，形成了一个复杂的空间结构，其中波能既可以从一个波转换到另一个波，也可以从下沉到湍流。因此，本建议旨在填补对海峡大振幅内波三维演化机制尚未研究的认识空白。不同于以往的许多理论研究都是利用压力的二维概念或流体静力近似，并排除非静力内混合的影响，本项目的目的是应用一个完全非线性的非静力数值模式，并结合观测资料来描述和量化海峡内与大振幅内波传播有关的动力过程。项目目标的实现是基于使用在直布罗陀海峡收集的详细观测数据集和应用最先进的麻省理工学院大气环流模式。

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.