Collaborative Research: Experiment on Internal Tide Scattering

合作研究：内潮汐散射实验

• 批准号: 0825266
• 负责人: Glenn Carter
• 金额: $ 57.48万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0825266&HistoricalAwards=false
• 关键词: Collaborative; Research; Experiment; Internal; Tide

Tides rival winds as an energy source for mixing in the deep ocean, yet the pathways of energy transfer from basin-scale tidal flows to turbulent mixing scales are not well understood. Over the past decade, many observations have shown barotropic tidal flow over steep, tall mid-ocean topography generates low-mode (large-scale) internal tides. Most of the energy lost from barotropic tides at these sites is carried away by internal tides with decay scales of O(1000 km). With few in situ observations away from internal tide generation sites, the ultimate fate of these low-mode internal tides and their energy is uncertain. This project will examine how topographic scattering of internal tides from large to small scales dissipates their energy via micro-scale mixing. Topographic scattering may also be a sink for wind-driven near-inertial internal waves. Hutchinson Seamount in the Line Islands Ridge will serve as an ideal test site, which lies in the path of energetic mode-1 internal tides emanating southward from the Hawaiian Ridge. Numerical models show the conversion of energy from a low-mode structure to a localized beam of energy with enhanced vertical shear and mixing. Altimetry provides unambiguous support for the model predictions of energy transfer from mode 1 to 2 downstream of the seamount. This project will observe the internal tide scattering process, quantify the associated mixing relative to the temporal and spatial structures of the scattered waves, verify model predictions, and improve model capabilities. Moorings will be deployed upstream (with respect to the incoming internal tides), on top, and downstream of the seamount for 150 days. A survey on R/V Revelle will provide spatial coverage at 19 stations with lowered acoustic Doppler current profiling/CTD/micro-structure to map 1) the incident and scattered wave fields near the seamount and 2) mixing via direct measurements, Thorpe scales, and fine-scale parameterizations. The mooring time series will isolate the tidal signal from background variability. A new numerical modeling study of the scattering will help refine the sampling plan and interpret the data. Internal tides impact the magnitude and inhomogeneity (in time and space- vertically and laterally) of diapycnal mixing. The meridional overturning circulation is likely not a heat engine, but is driven energetically by deep-ocean mixing. The relevance of global models, most with uniform mixing, of past or future climate is at issue if they are tuned to reproduce present observations, but do not include spatially and temporally inhomogeneous diapycnal mixing. Internal tide scattering is important where baroclinic tides are large and topography is tall and steep, such as in the Western Pacific and at mid-ocean ridges. The investogators will validate their numerical models against their experimental results for 2D and 3D topography in linear and nonlinear regimes. Graduate students and interns will gain experience with state-of-the-art instrumentation. Results will be broadly disseminated to the public by developing in cooperation with other researchers a Wikipedia entry on internal tides, their importance in mixing, and relevance to global circulation and climate. This website is often top ranked in internet searches and has the potential to reach millions of interested people in the general public as well as students. Publication of results in popular science magazines and websites will be sought via a press release from the Scripps Communications Office. Results will be disseminated in the oceanographic community by presentations at the International Union of Geophysics and Geodesy meeting in 2011 and the Ocean Sciences meeting in 2012 and by publishing in peer-reviewed journals.

潮汐与风竞争作为深海混合的能源，但能量从盆地尺度潮汐流到湍流混合尺度的传递途径还不清楚。在过去的十年中，许多观测表明，正压潮流在陡峭，高大的海洋中部地形产生低模式（大规模）的内潮。在这些站点的正压潮汐损失的能量大部分被内潮带走，衰减尺度为O（1000 km）。由于很少有远离内潮发生地点的现场观测，这些低模式内潮及其能量的最终命运是不确定的。这个项目将研究从大到小尺度的内潮地形散射如何通过微尺度混合耗散其能量。地形散射也可能是风驱动的近惯性内波的汇。莱恩群岛海脊的哈钦森海山将成为一个理想的试验场，它位于夏威夷海脊向南发出的高能模式1内潮的路径上。数值模型显示了能量从低模结构转换为具有增强的垂直剪切和混合的局部能量束。测高为海山下游从模式1到模式2的能量转移的模型预测提供了明确的支持。该项目将观察内部潮汐散射过程，量化与散射波的时间和空间结构相关的混合，验证模型预测，并提高模型能力。将在海山的上游（相对于内潮的到来）、顶部和下游部署系泊设备，为期150天。对R/V Revelle的调查将提供19个台站的空间覆盖面，并降低声学多普勒海流剖面/CTD/微结构，以绘制：（1）海山附近的入射和散射波场;（2）通过直接测量、索普尺度和精细尺度参数化进行的混合。系泊时间序列将把潮汐信号与背景变化隔离开来。一个新的散射数值模拟研究将有助于完善采样计划和解释数据。内潮影响的大小和不均匀性（在时间和空间-垂直和横向）的diapycnal混合。赤道翻转环流可能不是一个热力发动机，而是由深海混合产生的。全球模式的相关性，大多数与均匀混合，过去或未来的气候是有争议的，如果他们调整到重现目前的观测，但不包括空间和时间上不均匀的diapycnal混合。内潮散射在斜压潮汐大、地形高而陡的地方很重要，例如在西太平洋和大洋中脊。研究人员将验证他们的数值模型对他们的实验结果的二维和三维地形在线性和非线性制度。研究生和实习生将获得与国家的最先进的仪器经验。结果将通过与其他研究人员合作开发一个关于内部潮汐、其在混合中的重要性以及与全球环流和气候的相关性的维基百科条目，向公众广泛传播。该网站通常在互联网搜索中排名靠前，并有可能接触到数百万感兴趣的公众和学生。将通过斯克里普斯通讯办公室的新闻稿在科普杂志和网站上发表结果。将在2011年国际地球物理与大地测量学联合会会议和2012年海洋科学会议上介绍研究结果，并在同行评审期刊上发表研究结果，从而在海洋学界传播研究结果。