Velocity Structure of Internal Tide Beams Emanating from Kaena Ridge, Hawaii

Observations are reported of the semidiurnal (M-2) internal tide across Kaena Ridge, Hawaii. Horizontal velocity in the upper 1000-1500 m was measured during eleven similar to 240-km-long shipboard acoustic Doppler current profiler (ADCP) transects across the ridge, made over the course of several months. The M-2 motions are isolated by means of harmonic analysis and compared to numerical simulations using the Princeton Ocean Model (POM). The depth coverage of the measurements is about 3 times greater than similar past studies, offering a substantially richer view of the internal tide beams. Sloping features are seen extending upward north and south from the ridge and then downward from the surface reflection about +/- 40 km from the ridge crest, closely matching theoretical M-2 ray paths and the model predictions.