深海洋底地形上方内潮破碎的次级锋面潮汐波前详述
Detailing secondary frontal bore of internal tides breaking above deep-ocean topography
AI总结：
本研究通过系泊观测揭示深海洋底地形上方内潮破碎产生的次级波前，其湍流强度与主波前相当但翻转更大且触及海底，并呈现四分之一日周期性，表现为向前破碎特征。
摘要：
在陡峭的深海地形上方，内潮波可能发生剧烈破碎。相关的湍流混合对于重新悬浮物质、将其带离海底数十米以进行再分布具有重要意义。虽然在内潮（载波）从暖下坡相向冷上坡相转变的每次过渡期间，强湍流生成发生在主（锋面）波前周围，但次级波前可能约半个波周期后出现，在转向暖相之前。正如将从由200个高分辨率温度传感器组成的100天系泊阵列（位于北大西洋一座大海山的陡坡上方h=6-404米处）和一台低分辨率声学多普勒海流剖面仪（采样范围50至450米）所展示的那样，次级波前显示出与主波前周围相当的湍流强度，但它们通常表现出更大的翻转，且总是到达海底。次级波前与沿等深线流速的突然下降、上坡流（重新）增强（幅度可达|0.2|米/秒）以及一次谐波四分之一日周期性相关，这为湍流耗散率提供了一个谱峰。虽然每个波前外观各异，从弯曲如主波前到几乎垂直向上且带有参差不齐的边缘，但次级波前在一级近似下是向前破碎的，与向后破碎的主波前形成对比。
英文摘要：
Above steep deep-sea topography internal tidal waves may break vigorously. The associated turbulent mixing is important for resuspending matter, bringing it tens of meters away from the seafloor for redistribution. While intense turbulence-generation occurs around a primary (frontal) bore during each transition from warming downslope to cooling upslope phase of the internal (tidal) carrier wave, a secondary bore can appear about half a wave-period later before the turn to the warming phase. As will be demonstrated from a 100-day mooring array consisting of 200 high-resolution temperature sensors between h = 6-404 m above a steep slope of a large North-Atlantic seamount and a low-resolution acoustic Doppler current profiler sampling between 50 and 450 m, secondary bores show about the same turbulence intensity as around primary bores but they generally show larger overturns that always reach the seafloor. The secondary bores associate with a sudden drop in along-isobath flow speed, a (renewed) increase in upslope flow of up to |0.2| m s-1, and with first-harmonic quarter-diurnal periodicity which provides a spectral peak for turbulence dissipation rate. While each bore is different in appearance, varying from curved like a primary bore to almost straight upward with a ragged bore, secondary bores are in a first approximation forward breaking in contrast with backward breaking primary bores.
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