Where are the World's Highest Tides
The simple answer to the question is that the biggest tides anywhere are found in the Bay of Fundy in Canada. Extending nearly 100 miles (150 km) inland and over 30 miles (50 km) wide this inlet separates the Canadian provinces of New Brunswick and Nova Scotia.
On a big spring tide the difference between high and low tide can be as much as 60 feet (20 metres). The largest tidal range in the Bay of Fundy is observed at the head of the inlet in the Minas Basin. At the mouth of the bay, on the US / Canada border the range is significantly smaller, but still large enough to create a unique phenomena known as the "Reversing Falls" at the mouth of the Saint John River.
Mont Saint Michel in northern France is home to some of Europe's biggest tides
Factors affecting the size of the tide
There are a few reasons the tides are so huge in the Bay of Fundy, most importantly the shape and topography of the coastline. The funnel-shaped bay amplifies the effects of the tide, and as it gets narrower the only place for the water to go is upwards.
Another factor is the size and depth of the ocean, particularly relative to the depth of the location. In a larger, deeper ocean more water is moved by the gravitational forces of the moon and the sun. When this hits shallow water the effect is even more pronounced.
A further factor could be described as the "rhythm of the ocean". Every body of water has a natural period of oscillation and this is defined by the time it takes for the a wave to slosh from one side to the other. When this matches the regular oscillation of the tides it creates something known as tidal resonance and this is known to amplify the tidal range.
Table of highest tidal ranges
The highest tidal ranges in the world are found in the following locations. Please note these are average tidal differences and not the largest tidal variations on a given day.
| Location | Country | Average Tidal Range |
|---|---|---|
| Burntcoat Head, Bay of Fundy, Nova Scotia | Canada | 11.7 m (38.4 ft) |
| Ungava Bay, Quebec | Canada | 9.8 m (32 ft) |
| Avonmouth, Bristol | United Kingdom | 9.6 m (31.5 ft) |
| Sunrise, Cook Inlet, Alaska | United States | 9.2 m (30.3 ft) |
| Rio Gallegos, Santa Cruz Province | Argentina | 8.8 m (29 ft) |
| Granville, Normandy | France | 8.6 m (28.2 ft) |
| Banco Direccion, Magellan Strait | Chile | 8.5 m (28 ft) |
| Cape Astronomicheski, Kamchatka | Russia | 7.3 m (24.1 ft) |
| St. Helier, Jersey, Channel Islands | United Kingdom | 7.2 m (23.6 ft) |
| Derby, King Sound, Western Australia | Australia | 6.7 m (22 ft) |
Why are the tides bigger in the Atlantic Ocean?
If you were to look at all the locations above on a map you would notice they are nearly all located in the Atlantic Ocean. There are a couple of reasons for this;
Firstly is the resonance effect. The Atlantic has a natural oscillation period of about 12.5 hours which coincides quite neatly with that of the tidal cycle. The Pacific basin on the other hand has a natural period of about 25 hours which only coincides with one tide during the day.
Another feature of the North Atlantic is the close proximity of the continents. Europe and North America are pressed quite close together which causes some constriction of ocean's flow and in turn a higher tidal range.
Does distance from the Equator affect the size of the tide?
Looking at the list of locations above you may think there is a pattern with locations further from the equator having bigger high tides. But this is not the case.
It just so happens that the shape of the coastlines of the top few places is right and they also happen to be further from the equator. If we were to broaden the list you would see there are plenty of places near the equator that have a tidal range of over 17 feet (5m). The primary factor is one of topology.
Where are the smallests tides in the world?
The Mediterranean Sea has the smallest tides. Here the sea rises and falls only around and inch (2 to 3 centimetres) each day. This is because the Mediterranean is almost a lake and only joins the Atlantic through the narrow Straits of Gibraltar. It is this connection alone which causes any tidal variation.
Some might cite the Great Lakes of North America as having smaller tides, but they don't actually have tides at all. Any variation in water levels in the lakes is the result of climate and weather conditions.