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

合作研究：研究内潮汐到达塔斯马尼亚大陆坡时的能量耗散

• 批准号: 1434722
• 负责人: Amy Waterhouse
• 金额: $ 56.1万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1434722&HistoricalAwards=false
• 关键词: Collaborative; Research; study; energy; dissipation

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.

表面潮汐提供大约1太瓦的能量给内部潮汐，因为它们向上传播并经过大的地形特征。这些内潮的大部分能量以低模内潮的形式传播远离生成区域。这种能量的最终命运是未知的，对海洋属性的全球分布有很大的影响。以前的低模式内潮传播的研究已经观察到的内潮扩散的区域，并表现出复杂的干扰模式，使其难以关闭的能量预算。塔斯曼海与以前的地点不同，因为它被认为是世界上最有活力和最集中的内部潮汐光束之一。光束产生于新西兰南部，传播1,500公里，穿过塔斯曼海，并撞击塔斯曼大陆边缘。这个项目称为T梁将记录的衰减率集中的内部潮束，比较测量的通量收敛与新的湍流混合的原位测量，并调查的动力学过程负责观察到的衰减。T-Beam的结果将导致全球气候模式中内波诱导混合参数化的显著改进。分析的一个主要目标是比较原位内潮汐通量与卫星测高推断，后者是已知的偏置低，在存在强大的中尺度电流，但偏差的程度没有很好的记录。T-Beam研究人员与澳大利亚科学家建立了合作关系，他们将通过一套协同地质和生物分析来补充T-Beam测量。在实地调查期间，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获得海上经验，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大的代区域，包含一个长的能量和有限的内潮“梁”，并从远程产生的内潮庇护。拟议的实验将与NSF资助的塔斯马尼亚潮汐消散实验（T-TIDE）高度协调，该实验将研究内潮在塔斯马尼亚大陆坡浅滩上的消散情况。T-Beam将加强T-TIDE，提供入射内潮能通量的天气测量，减少对大陆坡上耗散的能通量比例的估计的不确定性。T-TIDE将通过提供额外的观测（自适应滑翔机采样和船上测量）来增强T-Beam，以帮助确定机制并更好地限制在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）提供了一个全面的内部潮汐生成过程。T-Beam和T-TIDE将共同完成这一生命周期，首次全面观测内潮束在开阔洋传播并在大陆坡消散的过程。施密特海洋研究所将提供与T-TIDE重合的28天的船舶时间。该项目将在可观测的内潮束中心部署一个为期两个月的系泊，对密度、速度和湍流进行密集的船基调查，以解析沿着和跨束空间结构，并对任意地形和中尺度变化情况下内潮束的形成、变化和消散进行数值模拟。