Langmuir Circulation - Internal Wave Interactions: Data and Modeling

基于直接动力学的混合层模式低估了长期观测记录中所看到的深度。一种增强混合的机制显然是缺失的。一种可能的机制涉及混合层的涡流运动穿透温跃层。另一种是由内波引起的增强剪切和/或倾覆(内波本身可以在当地或其他地方产生)。在这两种情况下，将温跃层的顺应性包括在风驱动混合模式中是很重要的，即研究主动强迫朗缪尔环流与高频内波的相互作用。为了回答这些问题，该项目将分析作为夏威夷海洋混合实验(HOME)的一部分收集的高分辨率数据。该仪器包括一个多波束地面侧扫描多普勒声纳系统，旨在确定混合层运动(例如朗缪尔环流)、定向表面波和与高频内波有关的表面应变场的长度和时间尺度，一个快速剖面CTDS，它提供的密度剖面在时间和深度上的分辨率足以估计翻转混合(Thorpe Scale)。一种8波束编码脉冲多普勒声纳系统，对水柱(从400米处向上和向下)的流动和剪切进行采样。以及风速和风向仪器。这个项目的中心问题是“内波是否影响混合层的运动，从而改变最上层跃层中的夹带和混合？”为了验证这一假设，研究人员将观察高频内波对表面速度结构的形式和动力学的影响，就像数据中看到的那样。这项建议的一个组成部分是使用从朗缪尔环流建模社区中提取的博士后，纳入复杂性逐渐增加的内波物理，并对输出进行重新采样以模拟数据。重点是深入的数据/模型比较，而不是模型开发本身：该战略涉及重新抽样和统计比较。预期的结果包括改进对海洋表层混合的理解和模型。智力上的优点。该项目的重点是大气/海洋系统中极其重要但尚未完全了解的一个环节：通过海洋表层的净混合。混合层和最上层的跃层在大气和深海之间形成了一个重要的屏障，控制着热量、动量、营养物质和温室气体的净通量。这一最上层对海洋生物也是至关重要的，它是光线和营养物质相遇的场景，也是污染物和污染物分散的地方。结果将有助于改善海气交换估计，从而改善气候影响，从而有助于改善决策所依据的信息。这些数据集、解释和结果将广泛传播，以增进科学理解，并促进进一步的重新审查和解释。将向公众和政策制定者提供摘要。拟议的活动将为博士后提供培训和教学机会。将积极发展跨学科和跨机构的伙伴关系和合作。

ABSTRACTOCE-0525256Straightforward dynamics-based mixed layer models underestimate the deepening seen in long-term observational records. A mechanism that augments mixing is apparently missing. One possible mechanism involves penetration of the thermocline by eddy motions from the mixed layer. Another is enhanced shear and/or overturns due to internal waves (which may themselves be generated either locally or elsewhere). In either case, it appears important to include the compliance of the thermocline in models of wind-driven mixing; i.e., to study the interaction of the actively forced Langmuir circulations with high-frequency internal waves.In order to answer these questions, this project will analyze high resolution data collected as part of the Hawaiian Ocean Mixing Experiment (HOME). The instrumentation includes a multi-beam surface-sidescan Doppler sonar system that is designed to define the length and time scales of the mixed layer motion (e.g. Langmuir circulation), directional surface waves, and surface strain fields associated with high-frequency internal waves, a rapid-profiling CTDs that provides density profiles with resolution in both time and depth sufficient to estimate mixing via overturns (Thorpe scales). an 8-beam coded pulse Doppler sonar system that samples flows and shears over the water column (upward and downward from 400m). and wind speed and direction instruments. The central question addressed by this project is "Do internal waves affect the mixed layer motions, and hence alter entrainment and mixing in the uppermost pycnocline?" To test the hypothesis that they do, the investigators will look at effects of high-frequency internal waves on the form and dynamics of the surface velocity structures like those seen in the data. An integral component of this proposal is employing a post-doc drawn from the Langmuir circulation modeling community, incorporating internal wave physics of incrementally increasing complexity, and re-sampling the output to mimic the data. The focus is on in-depth data/model comparisons, rather than on model development per se: the strategy involves re-sampling and statistical comparisons. The anticipated results include improved understanding and models of oceanic surface layer mixing. Intellectual merit. The project focuses on a link in the air/ocean system that is vitally important yet incompletely understood: net mixing through the surface layer of the sea. The mixed layer and uppermost pycnocline forms a crucial barrier between the atmosphere and deep ocean, controlling the net fluxes of heat, momentum, nutrients and greenhouse gases. This uppermost layer is also vital to marine life, setting the scene where light and nutrients meet, and where pollutants and contaminants are dispersed.Broader impacts. The results will help improve air-sea exchange estimates, and hence climate effects, thereby helping improve the information by which policy decisions are made. The data sets, interpretations, and results will be disseminated broadly to enhance scientific understanding and facilitate further re-examination and interpretation. Summaries accessible to the public and policy makers will be made available. The proposed activity will provide training and teaching opportunities for a post-doc. Partnerships and collaborations across disciplines and institutions will be actively developed.