Moored Mixing Measurements at the Equator

[04:24 . 13]理解海洋动力学的根本问题是我们对海洋如何混合的认识不足。反过来，这意味着用于预测未来气候情景的数值模式不能适当地参数化海洋混合，而海洋混合是其计算的一个敏感组成部分。在赤道地区尤其如此，因为那里的海流很强，近地表水分层，混合能量大且复杂，对大气的反馈至关重要。1984年至1991年间的一系列短过程实验揭示了产生湍流并因此在赤道混合的小尺度相互作用的定性性质。最重要的是，这些结果表明，混合的显著变化发生在时间尺度上，比在短船载工艺实验中可能取样的时间尺度更长。事实上，有强烈的迹象表明，混合率的变化——1992- 1993年厄尔尼诺之前的弱混合和1997- 1998年厄尔尼诺结束时的强混合——对厄尔尼诺/拉尼娜时间尺度上赤道海温的调节起到了正反馈作用。必须找到新的方法，在比船载过程实验更长的时间尺度上测量混合。在部署到深水系泊设施之前，将在当地设计、制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设备。目标是开发一种简单、可靠且价格合理的设备，可以轻松地集成到现有的系泊中。具体来说，一套10个设备将部署在TAO系泊系统上，初始阶段为6个月，功率为140W。此次部署将在系泊地点进行为期4天的湍流分析。系泊设备将提供数据来确定热的湍流扩散率（或浮力），从而确定每个传感器位置的湍流热通量。通过垂直布置许多装置，可以计算湍流热流的垂直散度，或由于湍流混合而产生的一团水的加热速率。通过长时间的部署，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，将研究与赤道湍流密切相关的窄带内波场的基本方面，从而有助于我们理解赤道暗流核心上方的混合和内波之间的物理关系。更广泛的影响：系泊混合测量的成功演示将导致一种负担得起且可靠的社区工具，可用于获取海洋其他地方的长期记录。这对于确定垂直混合作为对厄尔尼诺和拉尼娜等较长时间尺度事件的反馈过程的作用尤其重要。该工具将有助于可用于操作观测系统的测量套件。开发和科学分析将有助于培养一名研究生，几名暑期本科生和学院工程师。

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.