Simulations of motion in the bottom boundary layer induced by an internal standing wave*

Internal standing waves are a common feature in lakes where one dimension of the lake is significantly longer than the other. Barring effects of rotation of the Earth, the response to prolonged wind stress at the surface of the lake is a tilting of the thermocline which induces oscillation when the wind stress ceases. It is well known than the resulting oscillation can degenerate into non--linear wave trains which can facilitate vertical transport of material across the bottom boundary layer upwards into the water column. The literature is rich in experimental studies and numerical simulations showing the effects that passing solitary waves have on this process, but nothing to our knowledge has been done in the processes by which cross boundary layer transport occurs due to the presences of a seiche and the resulting wave motion induced by the seiche. Through the use of high resolution pseudo--spectral simulations in 2 and 3D, the vertical transport of a tracer in the presence of a seiche is quantified. The vertical transport is compared against existing data from numerical simulations of passing solitary waves.