The variability of mixing at the continental slope
The variability of mixing at the continental slope
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DOI：
10.1098/rsta.1990.0064
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发表时间：
1990-06
期刊：
影响因子：
--
通讯作者：
S. Thorpe;P. Hall;Martin White
中科院分区：
文献类型：
--
作者：
S. Thorpe;P. Hall;Martin White
大陆坡的海底边界层是等密度面与地形相交的区域。因此，它特别容易受到反射内部重力波以及被捕获的斜压斜坡波的影响。使用豪猪滩西坡的系泊装置进行的观测显示，在3000-4000米深处存在一个向北的顺坡流，延伸到离坡约20公里处，在约10公里（约10公里）内存在周期为2-9天的波浪。1 Rossby半径）。低频变化在更远的距离上占主导地位。潮汐有一个显着的频谱峰值，与第一次谐波明显的斜坡附近。边界层温度结构的测量已在1705米的赫布里底群岛斜坡和3447米的豪猪银行。在这两个地区的边界层结构是由不对称的M2变化的等密度面，与50 -100米的位移。在潮汐周期中出现了均匀的近床“混合”层，可达离海床约50米处，但这些层是短暂的，在等温线水位急剧上升后，仅持续潮汐周期的一小部分，后来被静态稳定条件所取代，延伸到海床几米之内。斜坡陷波也改变了平均温度梯度，并导致给定频率的反射内波临界或共振位置的变化。
The benthic boundary layer on the continental slope is a region in which isopycnal surfaces intersect topography. It is, in consequence, particularly subject to variability caused by reflecting internal gravity waves, as well as by trapped baroclinic slope waves. Observations made using an array of moorings off the west slope of the Porcupine Bank reveal the presence there of a northerly along-slope current at depths of 3000-4000 m, which extends to some 20 km off-slope, and of waves of periods 2-9 days trapped within about 10 km (ca. 1 Rossby radius) of the slope. Lower-frequency variations are dominant at greater distances. The tide has a significant spectral peak, with a first subharmonic apparent near the slope. Measurements of the temperature structure in the boundary layer have been made at 1705 m on the Hebrides slope and at 3447 m off the Porcupine Bank. In both areas the boundary layer structure is dominated by asymmetrical M2 variations in the isopycnal surfaces, with displacements of50-100 m. Uniform near-bed ‘mixed’ layers appear during the tidal cycle, reaching to some 50 m off the sea bed, but are transient, lasting for only a fraction of the tidal cycle following sharp rises in isotherm levels, later to be replaced by statically stable conditions extending to within a few metres of the sea bed. The slope-trapped waves also modify the mean temperature gradients and are responsible for variations in the locations at which reflecting internal waves of given frequency are critical or resonant.