On Tidal Resonance in the Global Ocean and the Back-Effect of Coastal Tides upon Open-Ocean Tides
On Tidal Resonance in the Global Ocean and the Back-Effect of Coastal Tides upon Open-Ocean Tides
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DOI：
10.3137/oc311.2009
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发表时间：
2009-12-01
期刊：
影响因子：
1.2
通讯作者：
Garrett, Chris
中科院分区：
文献类型：
--
作者：
Arbic, Brian K.;Karsten, Richard H.;Garrett, Chris
利用正演数值强迫阻尼全球潮汐模型和与陆架耦合的深海盆地强迫阻尼潮汐分析模型研究了半日潮汐高程的共振。分析模型分别包含深海和陆架中的经典半波长和四分之一波长共振，以及强迫尺度依赖性，该依赖性取决于公海重力波的相速度与天文强迫的相速度之比。在分析模型中，当深海和陆架分别以相同频率共振时，耦合系统中的共振会转移到比原始频率略高和略低的频率，从而在高程振幅与频率的关系图中看到“双凸块”。在共振的公海中添加陆架往往会减少公海潮汐，特别是当陆架也接近共振时。这种“反向效应”的大小由架子摩擦力控制。弱阻尼共振陆架对公海潮汐的反向影响比强阻尼陆架更大。数值模拟在很大程度上证实了分析模型的预测，至少是定性的。理想化模拟表明，大陆通过实现半波长共振来增强潮汐。使用真实的几何和地形进行的模拟，但天文强迫的纵向结构发生变化，显示了强迫规模对潮汐振幅的影响，与分析模型中看到的有点相似。在具有真实几何形状和地形的实验中，半日波段的频率扫描揭示了几个陆架区域的振幅和全球平均公海振幅的弱共振峰。最后，在模拟中可以看到陆架对公海的反向效应，其中共振沿海潮汐的位置被遮挡，结果公海潮汐高度显着改变（通常增加）。
The resonance of semi-diurnal tidal elevations is investigated with a forward numerical forced damped global tide model and an analytical model of forced-damped tides in a deep ocean basin coupled to a shelf. The analytical model contains the classical half-wavelength and quarter-wavelength resonances in the deep ocean and shelf, respectively, as well as a forcing-scale dependence which depends on the ratio of the phase speed of open-ocean gravity waves to that of the astronomical forcing. In the analytical model, when the deep ocean and shelf resonate separately at the same frequency, the resonance in the coupled system shifts to frequencies slightly higher and lower than the original frequency, such that a 'double bump' is seen in plots of elevation amplitude versus frequency. The addition of a shelf to a resonant open ocean tends to reduce open-ocean tides, especially when the shelf is also near resonance. The magnitude of this 'back-effect' is controlled by shelf friction. A weakly damped resonant shelf has a larger back-effect on the open- ocean tide than does a strongly damped shelf. Numerical simulations largely bear out the analytical model predictions, at least qualitatively. Idealized simulations show that continents enhance tides by enabling the half-wavelength resonance. Simulations with realistic geometry and topography but varying longitudinal structure in the astronomical forcing display an influence of the forcing scale on tidal amplitudes somewhat similar to that seen in the analytical model. A frequency sweep in the semi-diurnal band in experiments with realistic geometry and topography reveals weakly resonant peaks in the amplitudes of several shelf regions and in the globally averaged open- ocean amplitudes. Finally, the back-effect of the shelf upon the open ocean is seen in simulations in which locations of resonant coastal tides are blocked out and open-ocean tidal elevations are significantly altered (increased, generally) as a result.