Generation of inertia-gravity waves on the island shelf

Abstract

The data on currents near Oahu Island (Hawaii) measured using bottom acoustic current profilers placed at the edge of the shelf in Mamala Bay are analyzed. The variations in the amplitude of inertia-gravity waves (IGWs) are compared with those in background low-frequency currents using specially designed indicators of variations in the magnitude and direction of the currents. It is established that a good connection between the wave amplitude and variability of background currents is observed in cases of local IGW generation, especially if the currents rotate clockwise. This connection becomes weaker in the presence of waves coming from far sources, the role of which can be played, in particular, by IGWs excited by drain water jets flowing from a deep-water diffuser. The obtained results show that IGWs can be associated not only with the action of wind, but also directly with any restructuring of the current field inside the ocean.