Collaborative Proposal: Laboratory Studies of Stirring by Small-Scale Geostrophic Motions

合作提案：小规模地转运动搅拌的实验室研究

• 批准号: 0351892
• 负责人: Miles Sundermeyer
• 金额: $ 29.76万
• 依托单位: University of Massachusetts, Dartmouth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0351892&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Laboratory; Studies; Stirring

0351892/0351905Intellectual merit: Tracer release studies in the coastal and open ocean suggest that lateral dispersion on scales of 1 to 10 kilometer cannot be explained by shear dispersion or dispersion by lateral intrusions. Dispersion on these scales may be due to stirring by small-scale geostrophic motions, or vortical modes. Analytical and numerical modeling studies support this conclusion. However, a complete description of the generation of vortical modes via geostrophic adjustment of internal wave breaking events, their effect on lateral stirring, and their eventual dissipation is still lacking. The goal of the proposed laboratory experiments is to study lateral stirring by vortical modes formed by geostrophic adjustment of diapycnal mixing events., and to better quantify the importance of vortical mode stirring in the ocean. The main contributions of this work will be to test theoretical predictions for vortical mode stirring when internal wave forcing and breaking are present, and to provide a basis for parameterizing horizontal dispersion rates by vortical mode stirring in the ocean. Experiments will be conducted using the University of Rhode Island's Graduate School of Oceanography rotating tank facility. A 1 meter diameter, 30 centimeter deep uniformly stratified rotating tank will be used to model conditions in the ocean's stratified interior. Two methods will be used to generate diapycnal mixing events: 1) mechanical stirring in the form of localized grid-forced turbulence, and 2) a quasi-random field of internal waves and wave breaking generated by near resonant forcing of a mode-1 internal wave, and wave-wave interactions to scatter energy into higher modes. The formation of vortical modes and their effects on lateral stirring of a passive fluorescent dye will be examined using a combination of Particle Imaging Velocimetry (PIV), Laser Induced Fluorescence (LIF), and digital video analysis. A major advantage of the proposed laboratory studies over previous analytical and numerical studies is that diapycnal mixing events will ultimately be driven by internal wave breaking rather than some artificially imposed method of mixing. The proposed work will build extensively on analytical and numerical studies by the investigators and collaborators, which predict the amount of lateral dispersion caused by vortical mode stirring. However, these studies did not explicitly include breaking internal waves, but simulated their effects in terms of buoyancy flux. A major focus of this study will be to test theoretical and numerical predictions when large-scale internal wave forcing and diapycnal mixing by internal wave breaking are explicitly included. This will allow an assessment of the effects of large-scale internal waves, the conversion to potential energy through diapycnal mixing by internal wave breaking, and the transfer of energy into vortical modes.Broader impacts: The proposed work will help provide a quantitative description of vertical mode stirring on scales of 1-10 km in the ocean. Dispersion on these scales affects distributions of physical, biological, and chemical tracers, and is particularly important to understanding global ocean circulation and heat balances, since these scales are approximately the grid scale of state of the art global ocean circulation models. The project is a collaborative effort between the University of Rhode Island and the University of Massachusetts at Dartmouth. It will support one full time graduate student and one undergraduate summer intern per year for four years. We will attempt to fill these positions with candidates from underrepresented groups. The laboratory experiments will also be used to demonstrate internal wave dynamics for physical oceanography courses taught by the investigators.

0351892/0351905智力价值：沿海和公海的示踪剂释放研究表明，1至10公里尺度的横向扩散不能用剪切扩散或横向侵入扩散来解释。这些尺度上的色散可能是由于小尺度地转运动或涡旋模式的搅拌造成的。分析和数值模型研究支持了这一结论。 然而，仍然缺乏对通过内波破碎事件的地转调整产生涡旋模式、它们对横向搅动的影响以及它们最终消散的完整描述。所提出的实验室实验的目标是研究由地转混合事件的地转调整形成的涡旋模式的横向搅拌，并更好地量化海洋中涡旋模式搅拌的重要性。这项工作的主要贡献将是测试存在内波强迫和破碎时涡旋模式搅拌的理论预测，并为海洋中涡旋模式搅拌的水平分散率参数化提供基础。实验将使用罗德岛大学海洋学研究生院的旋转水箱设施进行。直径 1 米、深 30 厘米的均匀分层旋转水箱将用于模拟海洋分层内部的条件。将使用两种方法来生成二重混合事件：1）以局部网格强制湍流形式的机械搅拌，以及 2）由模式 1 内部的近共振力产生的内波和波破碎的准随机场波以及波与波的相互作用将能量散射到更高的模式。将结合使用粒子成像测速 (PIV)、激光诱导荧光 (LIF) 和数字视频分析来检查涡旋模式的形成及其对被动荧光染料横向搅拌的影响。与之前的分析和数值研究相比，所提出的实验室研究的一个主要优点是，二重混合事件最终将由内波破碎驱动，而不是由一些人为施加的混合方法驱动。拟议的工作将广泛建立在研究人员和合作者的分析和数值研究的基础上，这些研究预测了涡旋模式搅拌引起的横向色散量。然而，这些研究并没有明确包括破碎内波，而是根据浮力通量模拟了它们的影响。这项研究的一个主要重点将是在明确包括大规模内波强迫和内波破碎引起的二重混合时测试理论和数值预测。这将允许评估大规模内波的影响，通过内波破碎的二重混合转换为势能，以及将能量转移到涡旋模式。更广泛的影响：拟议的工作将有助于提供定量描述海洋中1-10公里尺度的垂直模式搅拌。这些尺度上的分散影响物理、生物和化学示踪剂的分布，对于理解全球海洋环流和热平衡特别重要，因为这些尺度大约是最先进的全球海洋环流模型的网格尺度。该项目是罗德岛大学和马萨诸塞大学达特茅斯分校之间的合作项目。它将在四年内每年支持一名全日制研究生和一名本科生暑期实习生。我们将尝试用来自代表性不足群体的候选人来填补这些职位。实验室实验还将用于演示研究人员教授的物理海洋学课程的内波动力学。