Collaborative Research: A study of the energy dissipation of the internal tide as it reaches the continental slope of Tasmania.

当表面潮汐向上传播并越过大型地形特征时，向内部潮汐提供大约1太瓦的能量。这些内潮的大部分能量以低模态内潮的形式从产生区传播出去。这种能量的最终命运是未知的，对海洋性质的全球分布有很大的影响。以往对低模态内潮传播的研究已经观察到内潮扩散的区域，并且表现出复杂的干涉模式，使得难以关闭能量收支。塔斯曼海与以前的地点不同，因为它被认为包含世界上最具活力和最集中的内部潮汐束之一。波束产生于新西兰南部，传播1500公里，穿过塔斯曼海，到达塔斯曼大陆边缘。这个名为T-Beam的项目将记录一个聚焦的内部潮汐束的衰减速率，将测量到的通量收敛与新的湍流混合原位测量结果进行比较，并研究导致观测到的衰减的动力学过程。T-Beam的结果将显著改善全球气候模式中内波混合的参数化。分析的一个主要目标是将现场的内部潮汐通量与卫星测高推断的潮汐通量进行比较；众所周知，后者在强中尺度洋流存在时偏低，但偏的程度没有很好的记录。T-Beam研究人员已经与澳大利亚科学家建立了合作关系，他们将用一套协同的地质和生物分析来补充T-Beam测量。在实地活动期间，T-Beam调查人员将准备新闻稿并发布每日博客。美国和澳大利亚的本科生和研究生将有机会进行海上体验、建模和分析。在T-Beam中，研究人员将获得塔斯曼海内部潮汐能量通量和耗散率的高分辨率估计。研究地点是有利的，因为它有一个单一的强生成区，包含一个长能量和受限的内潮“束”，并且可以免受远程产生的内潮的影响。拟议的实验将与美国国家科学基金会资助的塔斯马尼亚潮汐耗散实验（T-TIDE）高度协调，该实验将研究内部潮汐在塔斯马尼亚大陆斜坡上的耗散。T-Beam将通过提供入射内部潮汐能量通量的天气性测量来增强T-TIDE，这将减少估计在大陆坡上耗散的能量通量部分的不确定性。T-TIDE将通过提供额外的观测（自适应滑翔机采样和船载测量）来增强T-Beam，以帮助确定机制，并更好地约束在T-Beam期间观察到的公海衰减率。十年前，夏威夷海洋混合实验（HOME）提供了对内部潮汐产生过程的全面观察。T-Beam和T-TIDE将一起完成这一生命周期，提供首次全面观测内部潮汐束，当它通过开阔的海洋传播并在大陆斜坡上消散时。施密特海洋研究所提供与T-TIDE同步的28天船舶时间。该项目将在可观测的内潮梁中心部署一个为期两个月的系泊，进行密集的船载密度、速度和湍流调查，以解决沿梁和跨梁的空间结构，并在任意地形和中尺度变化的存在下对内潮梁的形成、变化和耗散进行数值模拟。

Surface tides supply about one terawatt of power to internal tides as they propagate up and over large topographic features. Most of the energy of these internal tides propagates away from the generation regions in the form of low-mode internal tides. The ultimate fate of this energy is unknown and has a large impact on the global distribution of ocean properties. Previous studies of low-mode internal tide propagation have observed regions where the internal tide was diffuse and exhibited complex interference patterns, making it difficult to close the energy budget. The Tasman Sea differs from previous sites because it is believed to contain one of the most energetic and focused internal-tide beams in the world. The beam is generated south of New Zealand, propagates 1,500 km across the Tasman Sea, and strikes the Tasman continental margin. This project called T-Beam will document the rate of decay of a focused internal tide beam, compare the measured flux convergence with novel in situ measurements of turbulent mixing, and investigate the dynamical processes responsible for the observed decay. The results from T-Beam should lead to significant improvement in parameterizations of internal-wave induced mixing in global climate models. A major goal of the analysis is to compare in situ internal tide fluxes with those inferred from satellite altimetry; the latter are known to be biased low in the presence of strong mesoscale currents but the extent of the bias is not well documented. T-Beam investigators have established collaborations with Australian scientists who will complement the T-Beam measurements with a suite of synergistic geological and biological analyses. During the field campaign, T-Beam investigators will prepare press releases and publish a daily blog. Undergraduate and graduate students in the United States and Australia will be offered the opportunity for at-sea experience, modeling and analysis.In T-Beam, the investigators will obtain high-resolution estimates of internal-tide energy flux and dissipation rates in the Tasman Sea. The study site is favorable because it has a single strong generation region, contains a long energetic and confined internal-tide "beam", and is sheltered from remotely generated internal tides. The proposed experiment will be highly coordinated with the NSF-funded Tasmanian Tidal Dissipation Experiment (T-TIDE), which will examine the dissipation of the internal tide as it shoals on the Tasmanian continental slope. T-Beam will enhance T-TIDE by providing synoptic measurements of incident internal-tide energy flux that will reduce uncertainties in estimates of the fraction of energy flux that is dissipated over the continental slope. T-TIDE will enhance T-Beam by providing additional observations (adaptive glider sampling and shipboard surveying) to help identify mechanisms and better constrain the open-ocean decay rates observed during T-Beam. A decade ago, the Hawaiian Ocean Mixing Experiment (HOME) provided a comprehensive look at the internal tide generation process. Together, T-Beam and T-TIDE will complete that life cycle by providing the first comprehensive observations of an internal-tide beam as it propagates through the open ocean and dissipates on a continental slope. The Schmidt Ocean Institute is providing 28 days of ship time coincident with T-TIDE. This project will deploy a two-month mooring situated in the center of the observable internal-tide beam, conduct intensive ship-based surveys of density, velocity and turbulence to resolve the along- and across-beam spatial structure, and numerically model the formation, variability, and dissipation of internal-tide beams in the presence of arbitrary topography and mesoscale variability.