Why do tides vary from place to place?

Why is the height of tides different around the Earth? There are various answers to this question. Let’s find out.

Why do tides differentiate around the world? The height of the tides on Earth is approximately 12 inches (30 cm) in the Baltic Sea, but it also sometimes reaches 50 feet (15 meters) in the Bay of Fundy off the coast of Canada. The differences between high and low tides vary widely from location to location. Why can tides be barely perceptible along some coastlines while causing massive tidal surges along others?

To get to the bottom of this, you need to know what causes the tides in the first place. The primary reason is the Sun’s and Moon’s gravitational pull on Earth and its seas. When this happens, water levels rise and create a flood crest in some locations while dropping and creating a depression elsewhere. Due to Earth’s rotation of one complete revolution every 24 hours, the location of these tidal waves will change over time.

The Sun’s and Moon’s relative positions to Earth and each other, as well as their orbital inclinations, all have a role in the intensity of the tidal forces they create. When the Sun, Earth, and Moon are in perfect alignments, such as during a new or full moon, the resulting tides are termed “spring tides,” and both the high and low tides are extreme. However, neap tides, which are less prominent than spring tides, occur when the Sun and Moon are at 90 degrees to each other. This, however, cannot account for the fact that certain coastlines consistently see foot-high tides while others never do.

Oceans with a greater surface area have bigger tides

Water bodies do not react equally to tidal forces around the globe. That’s why the height of tides varies depending on location. The size of a body of water is a major consideration in this regard. Compared to smaller seas like the Baltic or the North Sea, the water mass that may be moved by tidal forces in the ocean is far greater. 

Tidal waves from the Atlantic Ocean pour into the smaller North Sea, intensifying its own response to tidal forces, and this is why tides on the North Sea coast are still extremely prominent despite its relatively narrow link to the Atlantic.

However, the shape of the coastlines and the ocean floor are also important factors in determining the timing and magnitude of tidal waves. This is easy to picture using the shape of a river’s mouth as a model. Here, the water is being funneled into a smaller and shallower basin by the tidal wave. This accumulation causes the water level to be much greater at the funnel’s outlet than at its inlet.

Tides are amplified by the resonance of vibrating water

When the water’s surface is shaped in a way that makes it resonate with tidal forces, the results are amplified. One such oceanic area is Canada’s Bay of Fundy, where the rising and falling of water masses causes the bay between Nova Scotia and New Brunswick to see the highest tidal surges on record. On the other hand, tidal motions are minimal in smaller oceans or lakes due to adverse resonance circumstances.

The weather also has a big impact on the quantity of water available. A strong wind blowing inland from the sea, for instance, will force the water to go back toward the shore. The repercussions of this may be catastrophic. Storm surges may occur if the storm causes the water level to rise at the same time as the high tide. Low tides may also be caused by a strong wind blowing from land to sea.

Predicting water levels is challenging because of the interplay of so many variables, such as the Moon, the wind, the terrain, and the water itself. 

Since a long time ago, accurate studies of water levels and cutting-edge forecasting methods have been making tide predictions more accurate than ever before. 

By Bertie Atkinson

Bertie Atkinson is a history writer at Malevus. He writes about diverse subjects in history, from ancient civilizations to world wars. In his free time, he enjoys reading, watching Netflix, and playing chess.