A Global Geography of Internal-Wave Strain and Mixing from WOCE CTD Hydrography

全球海洋的内波应变和内波驱动的湍流混合将使用WOCE（世界海洋环流实验）水文数据集绘制超过18,000个CTD（电导率，温度和深度）剖面。将使用精细尺度参数化的仅应变版本来估计双周期扩散系数，该版本已被发现与剪切-应变版本在2因子内一致。拟议的工作将覆盖范围扩大5倍以上。这些混合预测将与由Luther和Decloedt（2010）对同一数据集进行的密度颠覆分析进行比较。将根据最近的进展和见解对精细尺度参数化进行改进。该项目扩展了之前的工作，该工作使用了~3500降低ADCP（声学多普勒电流分析器）和CTD剖面的剪切和应变。这项工作发现(i)大部分海洋的特点是与直接但稀疏的微观结构测量相一致的小扩散率，以及（ii）湍流极不均匀，热点与陡峭的地形有关。采样足以从垂直平流扩散方程推断出全球平均横流速度作为深度和纬度的函数。然而，大部分海洋取样不足，统计数据不足以表征单个盆地的经向翻转环流。提出的分析将提供一个更全面的海洋混合地理。对一个盆地接一个盆地的热盐环流的推断，将检验大部分的翻转是否像逆预算所显示的那样发生在印度洋。随着垂直分辨率的提高，内波应变的细化将成为可能。对于尺度不足以接近强强迫的担忧，将通过与同一数据集的密度翻转分析进行比较来解决。海洋混合是由微弱的广泛的内波驱动的混合还是非常强烈的热点主导，还有待观察。海洋混合的量化和理解仍然是物理海洋学中最棘手的问题之一。在一般环流模式（GCMs）中正确地参数化它对于正确地再现几个月到几千年时间尺度上的大范围特征至关重要，它不仅与环流有关，而且与天气预报、生物地球化学循环和长期气候有关。作为代表全球海洋模式中内波驱动混合的气候过程小组的成员，PI正在与数值建模人员密切合作，以改进gcm中内波驱动湍流混合的亚网格尺度参数化。与早期的工作一样，PI将可用于帮助其他研究人员在其他数据集中实现精细尺度参数化。这项工作的预测将向社区公开。PI将与华盛顿APL-U的外联资源合作，更好地教育公众波浪和混合在物理海洋学中的作用。

Internal-wave strain and internal-wave-driven turbulent mixing for the global ocean will be mapped using the WOCE (World Ocean Circulation Experiment) hydrographic data set of more than 18,000 CTD (Conductivity, Temperature and Depth) profiles. Diapycnal diffusivities will be estimated using a strain-only version of a fine-scale parameterization which has been found to agree with the shear-and-strain version to within a factor of 2. The proposed work represents a more than 5-fold expansion in coverage. These mixing predictions will be compared with those from density-overturn analysis being conducted by Luther and Decloedt (2010) on the same data set. Refinements to the fine-scale parameterization will be made based on recent advances and insights.This project expands on previous work which used shear and strain from ~3500 Lowered ADCP (Acoustic Doppler Current Profiler)and CTD profiles. That work found that (i) most of the ocean was characterized by small diffusivities consistent with direct but sparse microstructure measurements, and (ii) turbulence was extremely heterogeneous, with hotspots associated with abrupt topography. Sampling was sufficient to infer global-average diapycnal velocities as a function of depth and latitude from the vertical advective-diffusive equation. However, much of the ocean was undersampled and statistics were inadequate to characterize the meridional overturning circulation by individual basin. The proposed analysis will provide a much more comprehensive geography of ocean mixing. Inferences of the thermohaline circulation basin-by-basin will test if the bulk of the overturning occurs in the Indian Ocean as inverse budgets suggest. With higher vertical resolution, finer binning of internal wave strain will be possible. Concerns that the scaling falls short near strong forcing will be addressed by comparison with density-overturn analysis of the same data set. It remains to be seen whether ocean mixing is dominated by weak widespread internal-wave-driven mixing or very intense hotspots.Quantifying and understanding of ocean mixing remains one of the most vexing problems in physical oceanography. Its correct parameterization in general circulation models (GCMs) is critical to correctly reproducing a wide range of features on timescales of months to millennia, linking it not just to the circulation but also weather prediction, biogeochemical cycles and longterm climate. As a member of the Climate Processes Team on Representing Internal-Wave Driven Mixing in Global Ocean Models, the PI is working closely with numerical modelers to improve sub-grid-scale parameterizations for internal-wave-driven turbulent mixing in GCMs. As with the earlier work, the PI will be available to help other researchers with their implementations of the fine-scale parameterization in other data sets. Predictions from this work will be publicly available to the community. The PI will work with outreach resources at APL-U of Washington to better educate the general public in the roles of waves and mixing in physical oceanography.