Asymmetric mixing transport: A horizontal transport mechanism for sinking plankton and sediment in tidal flows
Asymmetric mixing transport: A horizontal transport mechanism for sinking plankton and sediment in tidal flows
复制标题
不对称混合输送：潮汐流中下沉浮游生物和沉积物的水平输送机制
DOI：
10.4319/lo.2001.46.2.0381
复制
发表时间：
2001
影响因子：
4.5
通讯作者：
P. Franks
中科院分区：
文献类型：
--
作者：
J. Pringle;P. Franks
本文描述了振荡潮流对下沉浮游生物或沉积物的净水平输运的机理。浮游生物或颗粒的平均运动是由涨落潮之间的垂直混合调制驱动的。在涨潮时，冷水被迫越过温水，造成了增强的垂直混合和下沉颗粒的再悬浮，使其更高地进入水柱。退潮时，情况正好匡威，下沉的颗粒在水柱中的位置较低。由于摩擦阻碍了底部附近的潮汐流动，这导致了向密度较小的水的净水平输送。因为密度较小的水往往较浅，这将倾向于将下沉的浮游生物和沉积物移向岸顶、海岸和海湾，即使没有任何平均海流。开发了这种水平传输的一维欧拉模型，并将其与具有先进湍流闭合方案的完全非线性二维模型中的颗粒运动进行了比较。在大多数情况下，欧拉模型可以预测颗粒的净水平运动，作为其下沉速度和可观察到的海洋学特性的函数。当粒子的下沉速度约为潮汐速度的七十分之一时，或相当于平均湍流速度尺度u* 的三分之一时，下沉粒子的平均水平速度最大。浮游生物和颗粒的这种水平运输不需要比简单的下沉更复杂的行为，以实现每天几公里的实际南极下沉速度的净水平速度。这种机制可能是在沿海地区补充和保留幼虫的一个因素，例如，乔治浅滩的扇贝幼虫。
A mechanism is described for the net horizontal transport of sinking plankton or sediment by oscillatory tidal flows. The mean motion of the plankton or particles is driven by the modulation of vertical mixing between flood and ebb. Cold water forced over warm water on the flood tide creates enhanced vertical mixing and resuspension of sinking particles higher into the water column. On ebb, the converse occurs, and sinking particles are lower in the water column. Since friction retards the tidal flow near the bottom, this leads to a net horizontal transport toward the less dense water. Because less dense water tends to be shallower, this will tend to move sinking plankton and sediment toward the crest of banks, toward the coast, and up embayments, even in the absence of any mean currents. A one‐dimensional Eulerian model of this horizontal transport is developed and is compared to particle motion in a fully nonlinear two‐dimensional model with an advanced turbulence closure scheme. The Eulerian model can, in most circumstances, predict the net horizontal motion of the particles as a function of their sinking speed and observable oceanographic properties. The mean horizontal speed of sinking particles is greatest when the sinking speed of the particles is about one‐seventieth of the tidal velocities, or equivalently, about one‐third of the mean turbulent velocity scale u*. This horizontal transport of plankton and particles requires no behavior more complicated than simple sinking to achieve net horizontal speeds of several kilometers per day for realistic planktonic sinking speeds. It is possible that such a mechanism is a factor in larval recruitment and retention in coastal regions, for example, scallop larvae on Georges Bank.