Horizontal circulation due to internal Kelvin waves breaking over a slope

In enclosed bays, solar radiation and freshwater inflow over the oceanic layer can cause strong stratification, creating a two-layer system. When wind forces are applied to a two-layer system, large amplitude internal Kelvin waves may occur. Since the sea floor is likely to have a mild slope at the head of enclosed bays, internal Kelvin waves may break over the slope. In general, when internal waves progress over a slope, internal wave breaking occurs, which results in mass transport due to onshore run-up and offshore intrusion under the density interface. However, understanding of mass transport and long term currents when internal Kelvin waves break over a slope is incomplete. This study thus aimed to investigate long term mass transport due to internal Kelvin wave breaking on a slope using a rotating tank with a two-layer system. The rotating tank had a length and width of 5 m and 0.4 m, respectively, and the specific density ratio was 0.02 with upper and lower layer thicknesses of 0.15 m. The angular velocity of the rotating tank was 2π/30 rad/s, the wave period of internal Kelvin wave was 11 s, and the slope was 3/20. As the amplitude of internal Kelvin waves reached a maximum at the lateral boundary, the breaking point of internal Kelvin waves was confirmed to occur at the lateral boundary over the slope. Interestingly, although offshore intrusion under the density interface did not occur due to the breaking, a unidirectional current from the lateral boundary to the perpendicular direction was evident, induced around the density interface due to the breaking of internal Kelvin waves. As a result, the unidirectional current was found to induce horizontal circulation in the upper layer in the region where the internal Kelvin waves break.