Collaborative Research: Systematic Direct Mixing Measurements within the Global Repeat Hydrography Program (SYSDMM)

合作研究：全球重复水文学计划 (SYSDMM) 内的系统直接混合测量

• 批准号: 1335282
• 负责人: Jonathan Nash
• 金额: $ 57.63万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1335282&HistoricalAwards=false
• 关键词: Collaborative; Research; Systematic; Direct; Mixing

To date, less than a thousand profiles of turbulence have been acquired in the deep ocean and these are concentrated in only a few geographic regions. As a result of this paucity of direct measurements, the distribution of mixing is inferred largely through proxies and parameterizations that have known limitations. Mixing budgets remain poorly constrained. The purpose of this pilot project is to demonstrate that systematic, repeated sequences of turbulent mixing over full-ocean depths can be obtained in a broad distribution throughout the global ocean. To accomplish this goal, the investigators in this project will deploy chi-pods - "turbulent mixing meters" on standard shipboard CTD/LADCPs package operated by the Global Repeat Hydrography Program. A few thousand turbulence profiles will be collected and analyzed over a three-year period. The chi-pods are self-contained instruments that have been quantifying mixing on equatorial moorings since 2005. They use fast response thermistors and precision accelerometers to measure microscale temperature gradients, from which the dissipation rate of temperature variance, ÷ and the eddy diffusivity of heat and other tracers. Unlike traditional velocity microstructure measurements based on shear probes, temperature microstructure measurements are not sensitive to platform vibration - a necessity for deployment on moorings with a surface expression or from a CTD rosette. The CTD-chi-pod has modifications that allow it to be easily clamped to a standard rosette with minimal impact during repeat hydrography operations, and has been proven successful in several recent pilot experiments in shallower waters.Intellectual Merit: Diapycnal mixing in the ocean interior has a strong influence on upper ocean heat and nutrient budgets, abyssal circulation, and water mass distributions. An initial attempt to develop and implement parameterizations of diapycnal mixing for large-scale models is underway as part of an NSF-funded Climate Process Team. The largest impediment to that effort is the incredible scarcity of direct turbulence observations, particularly those that cover the full water column depth. This project will demonstrate the feasibility and value of collecting a global dataset of microstructure observations that will be made publicly available as soon as possible after acquisition, following repeat hydrography protocols. The data will allow the PIs, as well as the broader scientific community, to calculate better global and regional averages of diapycnal mixing rates, explore underlying dynamics that control the geographic distribution of ocean turbulence, evaluate gradual changes in basin-averaged mixing rates, assess uncertainty and systematic bias in finescale shear and strain parameterizations of mixing that are becoming widely used, and validate turbulence parameterizations that will be going into the next generation of regional and climate models.Broader Impacts: The proposed measurements will be the first comprehensive set of direct mixing observations easily available to the broader community. These measurements can be used by a wide range of scientists to constrain everything from regional tracer budgets to biological nutrient fluxes to global energetics. The results will be particularly useful for testing and improving parameterizations of turbulent mixing being developed for global climate models (http://www-pord.ucsd.edu/~jen/cpt/), as diapycnal mixing rates remain one of the most influential tuning parameters in such models. This project will train one graduate student and give other students exposure to open-ocean observational techniques.

迄今为止，在深海中获得的湍流剖面不到1000个，而且这些剖面仅集中在少数几个地理区域。由于缺乏直接测量，混合分布主要是通过代理和参数化推断的，这些参数化具有已知的局限性。混合预算仍然没有受到很好的约束。这一试验项目的目的是证明，可以在全球海洋的广泛分布范围内获得整个海洋深度上系统的、重复的湍流混合序列。为了实现这一目标，该项目的研究人员将在全球重复水文计划操作的标准船上CTD/LADCP包上部署chi-pod-“湍流混合仪”。将在三年内收集和分析几千个湍流廓线。chi-pods是自2005年以来一直量化赤道系泊上混合的独立仪器。他们使用快速响应的热敏电阻和精密加速度计来测量微尺度温度梯度，从而测量温度变化的耗散率、温度梯度以及热和其他示踪物的涡流扩散率。与传统的基于剪切探针的速度微结构测量不同，温度微结构测量对平台振动不敏感，这是在具有表面表达的系泊系统或CTD玫瑰花上部署的必要条件。CTD-智荚有修改，使其能够很容易地夹紧到一个标准的玫瑰花与最小的影响，在重复水文操作，并已被证明是成功的，在最近的几个试点实验在较浅的沃茨。智力优点：在海洋内部的Diapycnal混合有很强的影响，上层海洋的热量和营养收支，深海环流，和水的质量分布。作为国家科学基金会资助的气候过程小组的一部分，正在进行为大尺度模型开发和实施穿透混合参数化的初步尝试。这一努力的最大障碍是令人难以置信的缺乏直接湍流观测，特别是那些覆盖整个水柱深度的观测。该项目将证明收集全球微观结构观测数据集的可行性和价值，在获得数据集后，将在重复水文学协议后尽快公开。这些数据将使研究所以及更广泛的科学界能够更好地计算出全球和区域的贯向混合率平均值，探索控制海洋湍流地理分布的基本动力学，评估流域平均混合率的逐渐变化，评估正在广泛使用的混合的细尺度剪切和应变参数化的不确定性和系统偏差，更广泛的影响：拟议的测量将是第一个全面的直接混合观测集，可方便地提供给更广泛的社区。这些测量可以被广泛的科学家用来限制从区域示踪剂预算到生物营养通量到全球能量学的一切。这些结果将特别有助于测试和改进为全球气候模式开发的湍流混合参数化（http：//www-pord.ucsd.edu/cnjen/cpt/），因为穿旋混合率仍然是这种模式中最有影响力的调整参数之一。该项目将培训一名研究生，并让其他学生接触公海观测技术。