Internal tidal beams and mixing near Monterey Bay
Internal tidal beams and mixing near Monterey Bay
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DOI：
10.1029/2010jc006592
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发表时间：
2011-03
影响因子：
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通讯作者：
T. M. Johnston;D. Rudnick;G. Carter;R. Todd;S. Cole
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文献类型：
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作者：
T. M. Johnston;D. Rudnick;G. Carter;R. Todd;S. Cole
使用安装在船上的声学多普勒电流剖面仪、拖曳式电导率-温度-深度仪器（SeaSoar）和安装在 SeaSoar 上的微电导率传感器相结合，观察了蒙特利湾附近海底海脊产生的内潮汐束的速度、密度和混合的空间结构。 16天内，从地表到400-670 m深度的3个<60 km的经向断面被占据了56次，采样模式与M2潮失谐。对给定纬度深度箱内的所有观测值进行平均会产生 M2 内潮汐的相位平均值。观察到的速度和位移方差被缩放以估计能量密度。能量密度的光束源自海底海脊，并在表面以减弱的幅度反射。这些结果与数值潮汐模型相比毫不逊色。向上和向下的光束显示出适度升高的湍流，该湍流沿着光束不均匀，并且其平均值比光束外部的平均值大约 50%。光束中的峰值几乎可以大一个数量级。与 MacKinnon-Gregg 参数化类似，耗散随着剪切和分层的增加而增加。超过一半的经向剖面发现了中间霞云层。它们的相位和方向表明，它们起源于模型中发现的次要、较弱的内潮汐产生地点，但在观测中却没有，这可能是由于中尺度变化影响了产生地点和波传播过程中的分层。沉积物的离岸运动是西向平均水流和内波驱动输送的结果。
The spatial structure of velocity, density, and mixing in an internal tidal beam generated at a submarine ridge near Monterey Bay was observed using a combination of vessel‐mounted acoustic Doppler current profilers, a towed conductivity‐temperature‐depth instrument (SeaSoar), and microconductivity sensors mounted on SeaSoar. Three <60 km meridional sections from the surface to 400–670 m in depth were occupied a total of 56 times during 16 days with the sampling pattern detuned from theM2tide. Averaging over all observations at a given latitude‐depth bin produces a phase average of theM2internal tide. Observed velocity and displacement variances are scaled to estimate energy density. A beam in energy density originates from a submarine ridge and reflects with diminished amplitude at the surface. These results compare favorably with a numerical tidal model. The upward and downward beams show modestly elevated turbulence, which is patchy along the beam and has mean values about 50% larger than those outside of the beam. Peak values can be almost an order of magnitude larger in the beam. Dissipation increases with increasing shear and stratification similar to the MacKinnon‐Gregg parameterization. Intermediate nepheloid layers were found in over half of the meridional sections. Their phasing and direction indicate that they originate at a secondary, weaker internal tidal generation site found in the model but not in the observations presumably due to mesoscale variability affecting stratification at the generation site and during wave propagation. The offshore movement of sediment is a result of westward mean current and internal wave‐driven transport.