Comparison of predictions of a numerical model and observations of tides in Bass Strait

Abstract

A depth-averaged numerical model is used to describe the tidal regime in Bass Strait. Tidal constants corresponding to the four major tidal constituents (M₂, S₂, O₁ and K₁) are calculated at the grid points of the model, and co-amplitude and co-phase contours drawn for each of the constituents. At 17 locations in Bass Strait, the computed tidal constants are in excellent agreement with those obtained from flow and sea-level data. The dominant tidal constituent is found to be the semi-diurnal, M₂, tide, which is predicted by the model with an accuracy of 10% in sea-level amplitude and 10º in phase. The M₂ tide in Bass Strait is generated by two oppositely travelling waves, one entering the eastern end and another entering the western end with a phase lag of about 3 h. Some amplification of these waves occurs as they move from the deep water into the much shallower continental shelf waters of the Strait, and their superposition causes a large tidal amplitude (up to 1.2 m) to occur in central Bass Strait. The other three constituents are much weaker than the M2 constituent, and are driven by tidal waves entering from the western end. They propagate eastwards, emerging at the eastern end with little change in amplitude throughout the Strait.