Internal Tides, Altimetry and the Subtropical Catastrophe: A Global Search for Loss of Low-Mode Internal Tide Energy at 28.9 degrees Latitude

内潮汐、高度测量和亚热带灾难：全球搜索纬度 28.9 度低模内潮汐能量损失

• 批准号: 0647743
• 负责人: Brian Dushaw
• 金额: $ 19.27万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0647743&HistoricalAwards=false
• 关键词: Internal; Tides; Altimetry; Subtropical; Catastrophe

Tides, which are caused by the gravitational pull of the sun and the moon, are commonly thought of as the regular rise and fall of the sea surface of approximately a meter. These tides, when they interact with topography, give rise to internal tides, in which water in the interior of the ocean may rise and fall over 100 meters. When these large amplitude waves break, they dissipate energy which plays a role in driving the large scale circulation of the world's ocean. Because the waves propagate long distances across ocean basins, they provide a means for tidal energy to be made available in regions far from where it was initially converted to internal waves. In recent years, there have been several major field experiments (HOME and IWAP) which aim to track these internal tides as they form and propagate away from Hawaii. Numerical models have shown that these internal tides are stable over long periods. They can be observed by satellite-based altimetry but to date these tidal analyses have been at individual locations. In the present study, internal tides will be tracked using a new analysis of satellite-based altimetry data. The principal investigator, an oceanographer at the University of Washington, will use frequency-wavenumber analyses to derive tidal harmonic constants using the TOPEX/Poseidon data which has near global coverage over a span of thirteen years, between 1992 and 2005. Recent theoretical work has suggested that there is enhanced dissipation at the critical latitudes of 28.9 degrees. However there has been little observational evidence of this phenomenon. A major goal of this study is to derive a quantitative measure of any enhanced dissipation near this latitude. In addition, the study will provide a better quantification of the overall scales of dissipation of these internal tides. The study has implications on the basic physics that governs how the large-scale ocean circulation affects the Earth's climate system. Consequently, the study could influence how these systems are modeled numerically.

潮汐是由太阳和月亮的引力引起的，通常被认为是海面大约一米的有规律的涨落。这些潮汐与地形相互作用时会产生内潮汐，海洋内部的水可能会上升和下降超过 100 米。当这些大幅度的波浪破裂时，它们会消散能量，从而在驱动世界海洋的大规模环流方面发挥作用。由于波浪在海洋盆地中传播很长的距离，因此它们提供了一种在远离最初转化为内波的地方提供潮汐能的方法。近年来，进行了几个主要的实地实验（HOME 和 IWAP），旨在跟踪这些内潮汐的形成和远离夏威夷的传播。 数值模型表明这些内潮汐在很长一段时间内是稳定的。它们可以通过基于卫星的测高法进行观测，但迄今为止，这些潮汐分析都是在各个地点进行的。在本研究中，将利用对卫星测高数据的新分析来跟踪内潮汐。首席研究员是华盛顿大学的海洋学家，他将使用频率波数分析法，利用 TOPEX/Poseidon 数据推导潮汐谐波常数，该数据在 1992 年至 2005 年的 13 年时间里几乎覆盖了全球。最近的理论工作表明在 28.9 度的临界纬度处存在增强的耗散。然而，这种现象的观察证据很少。这项研究的一个主要目标是得出该纬度附近任何增强耗散的定量测量值。此外，该研究还将更好地量化这些内潮汐消散的总体规模。 这项研究对控制大规模海洋环流如何影响地球气候系统的基础物理学具有影响。因此，这项研究可能会影响这些系统的数值建模方式。