权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Local Generation of Nonlinear Internal Waves on the Continental Shelf: Beams to Modes

大陆架上非线性内波的局部生成：波束到模态

基本信息

批准号：
1736698
负责人：
Karl Helfrich
金额：
$ 61.72万
依托单位：
Woods Hole Oceanographic Institution
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-10-01 至 2024-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736698&HistoricalAwards=false
关键词：
Local Generation Nonlinear Internal Waves

项目摘要

This project studies waves that are formed in the interior of the ocean, at the interface of water masses with different temperature and/or salinity properties. Such waves, called internal waves are generated when tidal flows interact with bathymetric irregularities in the interior of the ocean or the steep continental slope. These internal tidal waves tend to concentrate their energy along specific paths that resemble that of a light beam and propagate almost vertically in the water column. During the internal tide propagation, another type wave is generated, with different characteristics, called internal soliton waves. They propagate horizontally and have been linked to vertical mixing, cross-shelf transport of materials and larvae, and sediment mobilization. This study focuses on understanding the transition from principally beam-like internal tides to shorter nonlinear waves, especially in the coastal ocean. Laboratory, experimental work combined with theoretical and modelling activities will be used to understand the life-cycle of these energetic waves and inform modeling and interpretation of the coastal environment advancing our understanding of ocean mixing. Over the course of this work, the principal investigator will advise undergraduate students through the Woods Hole Oceanographic Institution (WHOI) Summer Student Fellowship Program on research topics directly related to the internal wave generation and propagation. Additionally, this study will contribute to the summer program in Geophysical Fluid Dynamics (GFD), held annually at WHOI, and it will involve GFD fellows with aspects of this research. This proposal will also contribute to maintaining the WHOI GFD Laboratory, a valuable resource to the scientific research community.Onshore propagating large-amplitude internal solitary waves are ubiquitous on continental shelves throughout the world's oceans. These waves emerge in packets from the nonlinear steepening of the internal tide as it propagates onshore. An under-appreciated aspect of this process is that the radiated internal tide is often dominated by vertically propagating beams generated on the continental slope, while the emergent solitary waves propagate horizontally with a single vertical mode structure. How the transition from principally beam-like internal tides to shorter nonlinear waves with modal structure occurs is not well understood, especially in the coastal setting. In particular, the time and length scales for emergence and the resulting properties of the solitary waves are of interest and will be examined as part of this study. A combination of laboratory experiments and numerical modeling work will be used to examine internal tidal beam generation at the continental slope and subsequent evolution of the beam as it propagates onto the confining topography of the shelf where it may eventually lead to the emergence of horizontally propagating modal internal solitary-like waves. The work will consider idealized stratifications, topography, and forcing (e.g. as single forcing frequency) in order to focus on the underlying dynamics and improve our understanding of this transition and the conditions that promote, or inhibit, the generation of these waves from the internal tide. The experimental component will be used to explore the generation and initial propagation of an internal wave beam onto a shelf and to provide a test for the subsequent modeling. The modeling will address limitations inherent in the laboratory work and use two complementary approaches. The first is an idealized multi-mode Korteweg-de Vries (KdV) model that generalizes previous linear, hydrostatic models of internal tide generation and captures the solitary wave dynamics. The second is to use the MIT general circulation model that allows exploration of additional factors not considered in KdV-type models.

该项目研究在海洋内部，在具有不同温度和/或盐度特性的水团的界面处形成的波浪。这种波称为内波，是潮汐流与海洋内部或大陆坡的水深不规则现象相互作用而产生的。这些内部潮汐波倾向于将它们的能量沿着特定的路径集中，这些路径类似于光束，并且在水柱中几乎垂直地传播。在内潮传播过程中，产生了另一种不同性质的波，称为内孤子波。它们横向传播，并与垂直混合、物质和幼虫的跨大陆架迁移以及沉积物移动有关。这项研究的重点是了解过渡，从主要梁状内潮汐较短的非线性波，特别是在沿海海洋。实验室，实验工作与理论和建模活动相结合，将用于了解这些高能波的生命周期，并为沿海环境的建模和解释提供信息，从而促进我们对海洋混合的理解。在这项工作的过程中，首席研究员将建议本科生通过伍兹霍尔海洋研究所（WHOI）暑期学生奖学金计划的研究课题直接相关的内波的产生和传播。此外，这项研究将有助于地球物理流体动力学（GFD）的夏季计划，每年在WHOI举行，它将涉及GFD研究员与这项研究的各个方面。该提案还将有助于维护WHOI GFD实验室，这是科学研究界的宝贵资源。陆上传播的大振幅内孤立波在世界各大洋的大陆架上普遍存在。这些波出现在数据包从非线性陡峭的内潮，因为它传播到岸上。这一过程的一个未被充分认识的方面是，辐射内潮往往是由大陆坡上产生的垂直传播波束占主导地位，而出射孤立波水平传播与单一的垂直模式结构。如何从主要梁状内潮的过渡到较短的非线性波与模态结构发生的是没有很好的理解，特别是在沿海设置。特别是，出现的时间和长度尺度和孤立波的性质是感兴趣的，并将作为本研究的一部分进行检查。将结合实验室实验和数值模拟工作，研究大陆坡内潮束的产生，以及潮束在传播到大陆架的局限地形上时的演变，最终可能导致出现水平传播的模态内孤立波。这项工作将考虑理想化的分层，地形和强迫（例如，作为单一的强迫频率），以专注于潜在的动态，并提高我们对这种转变的理解，以及促进或抑制这些波从内潮产生的条件。实验组件将用于探索内部波束到货架上的生成和初始传播，并为后续建模提供测试。建模将解决实验室工作中固有的局限性，并使用两种互补的方法。第一个是一个理想化的多模式Korteweg-de弗里斯（KdV）模型，概括了以前的线性，流体静力学模型的内部潮汐发电和捕获的孤波动力学。第二种是使用麻省理工学院的大气环流模型，允许探索KdV型模型中未考虑的其他因素。