3. Model results
We first sketch the behaviors of internal waves in one period, using an internal mode stream function which is defined as the difference between the original solutions and the solutions obtained by setting g = 0. Since the solution for g = 0 gives the barotropic flow that acts as the forcing (Lamb 1994), internal mode processes can be seen clearly in terms of internal mode stream functions.
3.1 M2 case
As described above, most of internal mode energy generated by the M2 flow propagates away as 1st-mode internal tides. Consequently, vertical mixing induced by waves generated by the M2 current is probably not strong enough to cause significant freshening in the Kuril Straits.
3.2 K1 case
The time series of the internal mode stream function in the K1 case (Fig. 3) shows quite different features from those in the M2 case, since the Kuril Straits is located over the critical latitude for the K1 tide and because the amplitude of the barotroprc K1 current is larger than that of the M2 current. For example, sill-scale cells (cells on the scale of the sill topography) do not propagate away, and, in contrast to the M2 case, intense disturbances exist on small scales.
First we describe the time evolution of the sill-scale cells. Although the K1 tide is subinertial and has no characteristic curves of propagation, clockwise cells are produced on both sides of the sill after 1.25 periods (the maximum rightward flow). These cells almost vanish at the end of rightward flow. Thus the sill-scale cells have the same frequency as the tidal frequency and do not propagate away because the K1 tidal period is longer than the inertial period at the Kurils.
