Of all the FAQs asked of us in the Lookout the favourite ones concern the tides; particularly about the fact that we have the second highest tidal range in the world. The conventional answer is that they are caused by the funnel shape of the Channel. This is undoubtedly true but I recently discovered on the questions page of the “New Scientist” another reason. The question that was asked was:”Why has The Bay of Fundy in Eastern Canada got the highest tidal range in the world?” The answer given by the Learned Journal was as follows:
If you partially fill a bath with water and then slosh the water backwards and forwards with your hand, you will set up an oscillation of sloshing. The frequency or period of this oscillation depends on the dimensions of the bath and the depth of water. If you now imagine the Bay of Fundy to be one half of the bath you can see the analogy. It so happens that the dimensions and average water depth in the Bay give rise to a natural oscillation which has a period of about 12 hours. Therefore the natural period of oscillation of water sloshing in and out of the Bay is reinforced by the cycle of the tides.
We can use the same theory to help explain our tidal range. The Bay of Fundy is rather more bath shaped than the Bristol Channel but I feel sure that the “Sloshing Effect” is also true here albeit perhaps to a slightly lesser effect. Interesting isn't it?