Internal-tide interactions with the Gulf Stream and Middle Atlantic Bight shelfbreak front
Internal-tide interactions with the Gulf Stream and Middle Atlantic Bight shelfbreak front
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DOI：
10.1002/2016jc011639
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发表时间：
2016-08-01
影响因子：
3.6
通讯作者：
Lermusiaux, Pierre F. J.
中科院分区：
文献类型：
--
作者：
Kelly, Samuel M.;Lermusiaux, Pierre F. J.
在中大西洋海湾地区的内部潮汐被发现显着的影响，存在的陆架前和墨西哥湾流，使用相结合的观测，方程和数据驱动的模型模拟。为了确定这些波的主导相互作用与潮下流，垂直模式的动量和能量偏微分方程推导出小振幅波在水平和垂直剪切平均流和在水平和垂直可变密度场。首先，在理想化的模拟与模式1内潮传播的能量平衡检查和沿着墨西哥湾流。其次，区域潮汐平均流相互作用的完全非线性动力学模拟与连续方程模式，它结合了现实的夏季中尺度特征和大气强迫。的shelfbreak前，它具有水平可变的分层，减少地形的内部潮汐发电约10%，并改变了波长和到达时间的本地生成的模式-1的内部潮汐在货架上，并在深渊。（分）中尺度的变化，在前面和货架上，以及夏季分层本身，也改变内部潮汐传播。墨西哥湾流产生O（20 mW m（-2））模态1内潮能量通量散度的异常区域，可用模态1能量平衡中的潮汐平均流项来解释。平流解释了大多数潮汐平均流的相互作用，这表明几何波理论解释了墨西哥湾流的模式1反射和折射。几何理论预测，离岸传播的模式1内潮以倾斜角度（与正常角度超过30度）撞击墨西哥湾流，被反射回沿海海洋，阻止其辐射到北大西洋中部。
Internal tides in the Middle Atlantic Bight region are found to be noticeably influenced by the presence of the shelfbreak front and the Gulf Stream, using a combination of observations, equations, and data-driven model simulations. To identify the dominant interactions of these waves with subtidal flows, vertical-mode momentum and energy partial differential equations are derived for small-amplitude waves in a horizontally and vertically sheared mean flow and in a horizontally and vertically variable density field. First, the energy balances are examined in idealized simulations with mode-1 internal tides propagating across and along the Gulf Stream. Next, the fully nonlinear dynamics of regional tide-mean-flow interactions are simulated with a primitive-equation model, which incorporates realistic summer-mesoscale features and atmospheric forcing. The shelfbreak front, which has horizontally variable stratification, decreases topographic internal-tide generation by about 10% and alters the wavelengths and arrival times of locally generated mode-1 internal tides on the shelf and in the abyss. The (sub) mesoscale variability at the front and on the shelf, as well as the summer stratification itself, also alter internal-tide propagation. The Gulf Stream produces anomalous regions of O(20 mW m(-2)) mode-1 internal-tide energy-flux divergence, which are explained by tide-mean-flow terms in the mode-1 energy balance. Advection explains most tide-mean-flow interaction, suggesting that geometric wave theory explains mode-1 reflection and refraction at the Gulf Stream. Geometric theory predicts that offshore-propagating mode-1 internal tides that strike the Gulf Stream at oblique angles (more than thirty degrees from normal) are reflected back to the coastal ocean, preventing their radiation into the central North Atlantic.