Tides in Fundy National Park

Fundy National Park

One of the most important draws for visitors to the region and to Fundy National Park is to experience the tides and the tidal flats of the Bay of Fundy. The effects of the tides on the shoreline and the local weather are easily seen and experienced from the park.

At Fundy National Park, the difference between high and low tide can be as much as 12 metres. At the head of the bay, the tide can rise 16 metres, the height of a four-story building.

At Alma Beach at the time of low tide, you can walk more than a kilometre from the high tide line across the tidal flats to the water's edge. Fundy's interpreters welcome you to guided walks along the coast. Walking on the bottom of the bay is a favourite pastime of visitors. This is, of course, is best done at low tide in the intertidal zone!

The highest tides in the world

Fundy's tides are the highest in the world because of an unusual combination of resonance (or seiche) and the shape of the bay. Like water in any basin, the water in the Bay of Fundy has a natural rocking motion called a seiche. You could compare this to the movement of water in a bathtub. Although the water in a bathtub sloshes from one end to the other and back again in a few seconds, it takes about 13 hours for the water in the bay to rock from the mouth of the bay to the head of the bay and back again.

The Atlantic Ocean tide rising and flooding into the bay every 12 hours and 25 minutes reinforces the rocking motion. To imagine this, picture an adult giving a gentle push to a child on a swing. Just a very small push, at the right time, is enough to make it go higher and higher. A pulse from the ocean tides sustains the seiche in the bay.

The Bay of Fundy's length is important. That's what makes the seiche frequency match the pulse from the Atlantic Ocean tides. The bay's shape is of secondary importance although still significant. The bay becomes narrower and shallower towards its head, forcing the water higher up the shores.

High and low tide

In the Bay of Fundy you can see two high and two low tides each day. The time between a high and low tide, on average, is six hours and 13 minutes.

If you come back to the same place two or three days in a row, you will notice that the water is at its highest and lowest about an hour later each day. This is because the tides work on a "lunar" or moon day which is 24 hours and 52 minutes long. While the earth is turning on its axis the moon is orbiting in the same direction around the earth and it takes one day and 52 minutes for a point on the earth to reappear directly beneath the moon.

Learn more about the interesting phenomena of Spring and Neap Tides.

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