内波、内潮汐沉积形成过程中内波传播方向与沉积物搬运方向相反的定量解释

Quantitative explanation of the opposite direction of internal wave propagation and sediment transport during the formation of internal wave and internal tide deposits

关键词:  内波、内潮汐沉积  密度界面  单向优势流动  波谷  波峰

Key words:  internal wave  internal tide deposits  density interface  unidirectional superior flow  wave trough  wave crest

摘要:

本文从海洋物理学角度出发,以内波波动理论为基础,通过建立两个不同密度的水层界面上的两层模型的波动方程对内波的传播特征进行定量解释。通过定量解释表达式可知:内波在两个不同密度的水层界面上传播时,两层内波流之水平速度方向相反,保持通过海底的整个截面的流通量为零。在密度界面之下,波谷处内波流的运动方向与内波前进方向相反,由于波谷相对于波峰更接近于海底,即波谷处截面积较小,故波谷下方的流速较波峰下方的流速大,容易形成与内波前进方向相反的单向优势流动,这种单向优势流动搬运沉积物的总趋势与内波的前进方向相反。

Abstract:

LaFond et al. (1962) advocated the opposite direction of internal wave propagation and sediment transport during the formation of internal wave and internal tide deposits. In the light of the fluctuation theory of internal wave and the marine physics, the present paper gives a quantitative explanation of the propagation of the internal wave by formulating the fluctuation equations of two-layer model on the water interface of different densities. According to the expression of quantitative explanation, when internal wave travels along the two-layer water interface of different densities, the horizontal directions are opposite between the two-layer internal waves, which keep the circulation quantity across the seafloor to be zero. Under the density interface, the moving direction of internal wave at wave trough is opposite to the progresive direction. Compared with the wave crest, the wave trough is closer to submarine, and the section at wave trough is smaller. Therefore the velocity under the wave trough is faster than that under the wave crest. This may easily cause the unidirectional superior flow in the opposite direction with the internal wave progression and the overall trend of the sediment transported by the unidirectional superior flow is in the opposite direction to the progression of internal wave.