AbstractA two-layer system with a deep lower layer in a semi-infinite ocean is investigated theoretically. Tidal forcing is applied, and expressions for an internal Kelvin wave are derived. Terms of second order in wave amplitude are retained, to get the wave averaged drift in the flow. The along-shore wave is damped due to friction. Accordingly, the damping in wave drift is compensated by a second order mean motion normal to the direction of wave propagation. Furthermore, the second order momentum equations are shown to relate to the divergence of wave energy flux, in the same manner as barotropic waves.
The derived internal Kelvin wave theory is applied to a semi-enclosed basin. This basin has a constriction at the basin entrance in order to enhance internal wave generation. On the northern hemisphere, the wave propagates anti-clockwise around the basin. A numerical model is applied to examine this wave motion. It is shown that the waves obtained may induce a net circulation in the basin.
An attempt is made to connect the results from the semi-enclosed basin to the Van Mijen fjord in Svalbard. This fjord is ice-covered a large part of the year, preventing energy input from wind and enhancing internal wave motion. Numerical model results demonstrate an internal wave as predicted. However, the model assumptions do not fully resolve the complexity of the system. Further investigation is needed to understand the motion in this particular fjord.