Bay of Fundy tides

The Bay of Fundy in Canada has the biggest tidal range on Earth, over 16 metres at Burntcoat Head. Commonly quoted estimates put the seawater that flows in and out with each tide at over 100 billion tonnes.

Context

Tides rise and fall because of the gravity of the Moon and Sun. In the Bay of Fundy the effect is greatly amplified by the shape of the bay. A tidal wave from the Atlantic enters a funnel that narrows and becomes shallower, and the water also sloshes back and forth at nearly the same rhythm as the tide, much like a bathtub pushed at the right moment. This resonance is the main reason the range is so large.

The greatest ranges are found at the head of the bay, such as at Burntcoat Head in Nova Scotia, where measurements of about 16 metres between low and high water have been recorded. The range depends on the time in the lunar cycle and the season, so typical tides are smaller than the record.

Volume estimates for the water moving in and out are often given as around 100 billion tonnes in each tide, though some sources give higher numbers for the whole bay. Treat the figure as an order-of-magnitude comparison.

The tides shape the coast, create mudflats rich in food for migrating shorebirds, and have long been studied as a potential source of tidal power.