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It is amazing how little we know and understand the tides and the resulting currents. To the Northwest mariner, the tides are critical to safe passage. By reading Tides: The Science and Spirit of the Ocean by Jonathan White, mariners can benefit from and appreciate a deeper understanding of the tides and what makes them work.

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Tides: The Science and Spirit of the Ocean by Jonathan White

In Tides: The Science and Spirit of the Ocean, sailor, surfer, and author, Jonathan White captures the story of the tides and explains their historical, spiritual and technical background to understanding this global force. He tells the story through a worldwide journey to different places where the tides are critical to existence or can be downright lethal. The book describes how tides are generated and how they play such a crucial part of how the earth works. 

History of Understanding the Tides

Hundreds of years ago when the tides were not understood, the thinking was that the tides were the earth’s breathing. Newton, Halley, and Galileo each made huge advances in understanding our of tides and how they are generated by gravitational pull. The findings of the original scientist and philosophers were controversial. The Catholic church, and its popes viewed the tides as being controlled by God. Galileo was placed under house arrest by Pope Urban VIII to keep him from communicating and sharing his explanations of the planets, gravity, and the tides.

What we know now, is that tides are generated by the gravitational pull from the moon and the sun primarily. They are also affected by many other factors such as friction with the rotation of the earth and even oscillations of bodies of water and their natural frequency.

Imagine that we have a force in the world that has no physical connection. There is nothing touching and this force can reach across millions of miles. This force can move water and other tangible things. We take it for granted now but the early theories hundreds of years ago could not understand this force and assumed it was the work of God.

Tides and Air Pressure

Just when you have figured out gravity and its effect on the tides, consider that the predictable and plot-able tides can be affected by the changing air pressure systems in our weather. A low-pressure system over a large area can result in less weight on the earth’s surface water. The result could be as much as a 3-foot increase in the tide height in a place like Los Angeles.

Next time your tide guide is off by feet or the current strength is more than what is predicted check the barometric pressure. Pressure systems are also why extreme inclement weather timed with a full moon can lead to severe flooding such as during a hurricane.

Testing Your Tidal Knowledge

Throughout the book are interesting tide factoids.

Did you know:

  • The tides are powered by the gravitational pull of the moon, but did you know the gravitational pull of the sun is also a factor?
  • Since the moon is in an elliptical orbit, the timing of the tide changes by the season in our lunar year.
  • Generally, we know that the timing of the tides is in a 28-day cycle and shifts by 50 minutes every day.
  • The strongest tides are on a Spring Tide. This term derives from the Anglo-Saxon term springan, meaning to rise, burst or swell, typically on a full moon or a new moon.
  • The lightest tides are called Neap Tidesfrom the Anglo-Saxon term nepmeaning lacking or scanty happening on the half-moon.
  • When the moon, earth, and the sun are in alignment, it is called syzygy. Now when you see a boat named Syzygy, you will know what it means.
  • When the moon is in perigee, or at its closest in its elliptical orbit, the tidal ranges are at their highest.
  • The world’s largest tidal range is just over 53′ in the Bay of Funday in Canada. The extreme tide is a result of the shape of the bay.
  • The incoming tide can run at high speeds creating a lethal situation for man and animals as it floods across low-lying areas creating a tidal bore.

My Thoughts on Tides: The Science and Spirit of the Ocean

The author, Jonathan White, lives in the Northwest and I appreciated that he included familiar examples of our tidal conditions and the resulting currents in places like Deception Pass, Seymour Narrows and the triple rapids north of Desolation Sound.

I also liked that he included a section about the future and how tidal energy all over the world could generate much-needed power. In fact, tidal power could meet about 1/3 of our power requirements. We have put an enormous amount of research and effort into solar and wind power, and for the most part, tidal power is untapped other than a few test installations. (Tidal power installations are being tested in Dent Rapids and Blind Channel. There have also been proposed tests planned for Guemes Channel and Deception Pass.)  While the engineering problems of harnessing the forces of tidal power are massive, they are workable. Unlike solar and wind, the tides are predictable and sometimes can offer their own means of storing power. And, tides are renewable and pollution free.

In conclusion, the story of Tides: The Science and Spirit of the Ocean is a good read and includes history, travel, science and a future. Tides… makes a great summer read while sitting on the boat as it moves up and down by virtue of the tides.

~ Mark Bunzel

Tides: The Science and Spirit of the Ocean

By Jonathan While

Hardcover, 360 pages

Available at Captains Nautical in Seattle, bookstores, and

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