Moored Mixing Measurements at the Equator

0424133理解海洋动力学的一个基本问题是我们对海洋如何混合的知识不足。反过来，这意味着用于预测未来气候情景的数值模型不能正确地参数化海洋混合，这是其计算的敏感组成部分。在赤道地区尤其如此，那里的洋流很强，近地表沃茨分层，混合过程充满活力且复杂，对大气的反馈至关重要。1984年至1991年期间的一系列短期过程实验揭示了小尺度相互作用的定性性质，这些相互作用是产生湍流并因此在赤道混合的原因。最重要的是，这些研究表明，混合的显著变化发生在比短船载过程实验可能采样的时间尺度更长的时间尺度上。事实上，有强烈的暗示，混合率的变化-弱混合之前，1992 - 93年厄尔尼诺和强混合，以结束1997 - 98年厄尔尼诺-有助于积极反馈调制赤道SST厄尔尼诺/拉尼娜时间尺度。必须找到比船载过程实验更长的时间尺度上测量混合的新方法。在部署到深水系泊之前，将设计、建造和测试一个使用玻璃珠热敏电阻测量温度微观结构的独立装置。其目标是开发一种简单、可靠和负担得起的设备，易于集成到现有的系泊系统中。具体而言，一套10个装置将部署在0 140 W的TAO系泊上，初始时间为6个月。该部署将通过在系泊位置进行4天的湍流剖面分析来增强。系泊设备将提供数据以确定热的湍流扩散率（或浮力），从而确定每个传感器位置处的湍流热通量。通过在垂直方向上部署多个装置，可以计算湍流热通量的垂直发散，或由于湍流混合引起的水的加热率。通过长时间部署，将评估湍流混合对与长时间尺度事件相关的海面温度变化的影响。此外，窄带内波场的基本方面，密切相关的赤道湍流将进行调查-从而有助于我们理解的混合和内波的赤道暗流的核心以上的物理关系。更广泛的影响：停泊混合测量的成功示范将导致一个负担得起的和可靠的社区工具，可用于获得长期记录在海洋的其他地方。这在确定垂直混合作为对较长时间尺度事件（如厄尔尼诺和拉尼娜）的反馈过程的作用方面尤为重要。这一工具将有助于为业务观测系统提供测量套件。开发和科学分析将有助于一名研究生，几个暑期本科生和大学工程师的培训。

0424133A fundamental problem in understanding ocean dynamics is our inadequate knowledge of how the ocean is mixed. In turn, this means that numerical models used to predict future climate scenarios cannot properly parameterize oceanic mixing, which is a sensitive component of their computations. This is especially true in equatorial regions, where currents are strong, near-surface waters are stratified, mixing is energetic and complex, and feedbacks to the atmosphere are critical. A series of short process experiments between 1984 and 1991 revealed the qualitative nature of small-scale interactions responsible for generating turbulence and thereby mixing at the equator. Most importantly, these revealed that significant variations in mixing occurred on time scales longer than could possibly be sampled in short ship-borne process experiments. Indeed, there are strong hints that variations in mixing rates-weak mixing prior to the 1992-93 El Nino and strong mixing to conclude the 1997-98 El Nino-contribute positive feedback toward modulating equatorial SST on El Nino/La Nina time scales. New ways to measure mixing on time scales longer than a ship-borne process experiment must be found.A self-contained device to measure temperature microstructure using glassbead thermistors will be designed, build and tested locally before being deployed on a deep-water mooring. The objective is to develop a simple, reliable and affordable device to be readily integrated into existing moorings. Specifically, a suite of 10 devices will be deployed on the TAO mooring at 0 140W for an initial period of 6 months. This deployment will be augmented by 4 days of turbulence profiling at the mooring location. The moored devices will provide the data to determine the turbulent diffusivity of heat (or buoyancy) and hence the turbulent heat flux at each sensor location. By deploying many devices vertically, the vertical divergence of the turbulent heat flux, or the heating rate of a parcel of water due to turbulent mixing will be computed. By deploying over a long time period, the influence of turbulent mixing on sea surface temperature changes associated with long time scale events will be assessed. As well, fundamental aspects of the narrowband internal wave field that are closely linked to turbulence at the equator will be investigated - thereby contributing to our understanding of the physical relationship between mixing and internal waves above the core of the Equatorial Undercurrent. Broader Impacts: The successful demonstration of moored mixing measurements will lead to an affordable and reliable community tool that can be used to obtain long records elsewhere in the ocean. This is especially important in determining the role of vertical mixing as a feedback process to longer time scale events such as El Nino and La Nina. This tool will contribute to the measurement suite available for operational observing systems. Development and scientific analysis will contribute to the training of one graduate student, several summer undergraduate students and College engineers.