Plenary Talk 9

R. Dwi Susanto, PhD

Chasing Skyscraper Internal Waves for Submarine Safety Using Synthetic Aperture Radar Data

The Indonesian seas, with complex coastline geometry and bathymetry, narrow strait and passages, stratified waters, and strong throughflow and tidal currents, are favorable places for the generation and propagations of rigorous ocean internal waves. Internal waves are generated when the interface between layers (density stratification is strong) is disturbed. The disturbances are often caused by strong tidal flow passing over shallow ridges such as sill between Bali-Nusa Penida-Lombok. For Lombok Strait, the forcings are a combination of tidal current and Indonesian throughflow (ITF). Ocean internal waves typically have wavelengths from hundreds of meters to tens of kilometers and periods from several minutes to several hours. Their amplitudes (peak to through) often exceed 100m. Orbital motions of the water particles associated with internal waves have the largest radius at the pycnocline depth, which decreases downward and upwards from this depth. Tidally generated internal waves are usually nonlinear (solitons) and often occur in the form of wave packets. These internal waves are significant mechanisms for the transport of momentum and energy. Hence, it is dangerous for mid-ocean divers and submarine safety. The study case of the Nanggala 402 submarine that sunk in north Bali due to these humongous waves will be explained.