Tidal resonance

[3] Most of the resonant regions are also responsible for large fractions of the total amount of tidal energy dissipated in the oceans.

With a narrower shelf, there is still a resonance but it is mismatched to the frequency of the tides and so has less effect on tidal amplitudes.

However the effect is still enough to partly explain why tides along a coast lying behind a continental shelf are often higher than at offshore islands in the deep ocean (one of the additional partial explanations being Green's law).

In the deep ocean, where the depth is typically 4000 m, the speed of long waves increases to approximately 200 m/s.

The increased speed of long waves in the deep ocean means that the tidal wavelength there is of order 10,000 km.