How can different ports have different form factors and thus different types of tide? After all, the tide generating force field is a long wave that spans the entire globe. All ports should therefore experience the same tidal forcing, which should produce the same tidal response. The reason is found in the mismatch of scales between the forcing field and the dimensions of the ocean.
The earth is not covered with water of equal depth everywhere, and the world ocean is divided into different ocean basins.
All ocean basins are much smaller than the tidal wave that could be produced by direct action of the tidal forcing field. The observed tides are therefore never the result of water following the tide generating force field directly; they are a resonance phenomenon.
Imagine a pair of small rectangular fish tanks (ocean basins) on a table (earth). The table is being moved back and forth. (This is the tide generating force, but for the purpose of the experiment we use an earth the size of a table, so we have to shorten its period somewhat, to something like 1 - 2 seconds). What do you think will happen to the water level in the fish tanks? Will the water slosh back and forth?
© 2000 M. Tomczak