Impact of Nonlinear Barotropic Tides in the North Pacific

北太平洋非线性正压潮汐的影响

• 批准号: 1460022
• 负责人: Douglas Luther
• 金额: $ 38.99万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-03-15 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1460022&HistoricalAwards=false
• 关键词: Impact; Nonlinear; Barotropic; Tides; North

The daily surface tides in the ocean, forced by gravitational perturbations arising from the motions of Earth and its Moon, exert a profound influence on the biology, chemistry, geology and circulation in both pelagic and coastal environments. As more accurate models of the tides have been developed, it has been realized that non-linear interactions among the tides in the shallow seas and continental shelves (which are all forced by the pelagic tides) result in a flow of energy back into the open ocean, but at altered frequencies and wavelengths. The impact of this energy flux can have significant consequences not only for modeling the diurnal and semi-diurnal tides themselves, but for the energetics of phenomena dependent on the tides such as abyssal mixing. This study explores two lines of research. The first is to determine how much the coastal non-linear tides "contaminate" what is generally considered to be the linear diurnal and semi-diurnal tides in the pelagic ocean. The second addresses the question of whether the flux of coastal nonlinear tide energy dominates the entire suite of surface gravity wave motions in the pelagic ocean at periods shorter than the tides, even as short as 15 minutes, a possibility that has ramifications both for the ocean's energy budget and other geophysical phenomena (e.g., Earth's "seismic hum"; fragmentation of ice shelves) that are now known to depend on these waves. The project involves training of one graduate student.The broad objectives of this study are to elucidate, using observational tools, (i) the nature (e.g., amplitude, structure) of the pelagic, barotropic, nonlinear tides, especially within the diurnal and semi-diurnal tide bands; (ii) the specific source locations for the energy in the pelagic, barotropic, nonlinear tides; (iii) the flow of energy from the principal, linear barotropic tides to gravity waves in other frequency bands; (iv) the nature (e.g., isotropic or not) and sources of the gravity wave energy at periods of 15 minutes to 2 hrs. These objectives will be accomplished by analyses of existing long ( 1 year) bottom pressure records in the North Pacific that well observe these waves and tides. The methodologies include least squares harmonic analysis and a variety of auto- and cross-spectral techniques, some borrowed from seismology.

每日海洋表面潮汐受地球及其月球运动产生的重力扰动的影响，对大洋和沿海环境中的生物、化学、地质和环流产生深远的影响。随着更精确的潮汐模型的发展，人们认识到，浅海和大陆架的潮汐之间的非线性相互作用（都是由远洋潮汐造成的）导致能量流回到公海，但频率和波长有所改变。这种能量通量的影响不仅可以对模拟昼夜潮汐本身产生重大影响，而且可以对依赖于潮汐的现象（如深海混合）的能量学产生重大影响。本研究探讨了两条研究路线。第一个是确定沿海非线性潮汐“污染”通常被认为是远洋中的线性昼夜潮汐和半日潮汐的程度。 第二个解决的问题是，沿海非线性潮汐能量的通量是否在比潮汐更短的周期内主导了远洋海洋中的整个表面重力波运动套件，甚至短至15分钟，这种可能性对海洋的能量预算和其他地球物理现象都有影响（例如，地球的“地震嗡嗡声”;冰架的碎裂），现在已知依赖于这些波。该项目包括培训一名研究生。这项研究的主要目标是利用观测工具阐明：（i）振幅、结构）;（ii）远洋、正压、非线性潮汐中能量的具体来源位置;（iii）从主要的线性正压潮汐到其它频带中重力波的能量流动;（iv）海洋潮汐的性质（例如，各向同性或非各向同性）和周期为15分钟至2小时的重力波能量源。这些目标将通过分析北太平洋现有的长期（1年）海底压力记录来实现，这些记录可以很好地观察这些波浪和潮汐。这些方法包括最小二乘谐波分析和各种自动和交叉频谱技术，其中一些是从地震学中借来的。