Myths in Surfing: Are Cold Water Waves Heavier?

Tony Butt

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Updated 188d ago

We adults often find it easiest not to question things. How often have you heard people repeat phrases like: “Red sky at night, shepherd’s delight” mostly without the slightest clue where it comes from?

There are literally thousands of axioms or proverbs like this. They form an essential part of our language and culture, and we surfers are just as guilty of using them as anybody else. Sometimes we make statements about the surf by repeating things we’ve heard other people say without really questioning them. Some turn out to be totally accurate of course, while others are partly misunderstood (see my article on offshore canyons, for example), and others are just total gibberish.

The other day, a friend of mine asked me if it was true that warm water makes the waves more powerful. I had only heard the opposite – that cold water seems to make the waves heavier. My friend said the places he had surfed on tropical islands such as in Hawaii, Fiji or Tahiti, definitely had more powerful waves than the colder waters of England, Ireland or the East coast of North America.

I couldn’t have agreed more. But I assured him that it wasn’t the water temperature itself that made the waves more powerful; there must be some other factor at play.

I thought about it. At most of the places he mentioned the waves broke on coral reefs off oceanic islands. Now, coral only grows if the water temperature is above about 26°C, so you would never find it in Newquay, Bundoran or New Jersey. And waves on coral reefs often break quite abruptly because of the sudden transformation from deep to shallow water, typical of oceanic islands with deep water just offshore.

So, if this was the case, even though the temperature of the water had no direct relation to the power of the waves, they were both linked via a third factor: namely the coral and the lack of continental shelf.

On the left, we have Nic Von Rupp at jacking Mullaghmore (image by Tim Borrow) and the right, Dane Gudauskas charging Cloudbreak (by Brad Scott) - but it is not water temperature that adds to the heavy factor of a wave.

On the left, we have Nic Von Rupp at jacking Mullaghmore (image by Tim Borrow) and the right, Dane Gudauskas charging Cloudbreak (by Brad Scott) - but it is not water temperature that adds to the heavy factor of a wave.

This kind of thing often catches people out in scientific studies. Two variables are found to be highly correlated; and at first glance it looks like there is a cause-and-effect relationship between them. But there is a sneaky third variable, having separate cause-and-effect relationships with each of the first two. It is this third factor which is causing the first two to coincide, even though the first two are not directly related to each other.

Here’s another example: “The wind always changes with the tide”. Along the coast where I live, sometimes you hear people stating that the wind will definitely swing from offshore to onshore as soon as the tide turns from dropping to rising. They imagine a cause-and-effect relationship between the wind and the tide. Perhaps it is difficult not to believe if you’ve lived on the same coastline for 40-years and you see it happening all the time.

....but what about frozen waves?

Well, the wind and the tide are probably not directly connected. It is more likely due to a third factor. Time. At most spots along the west coast of Europe, spring low water occurs around the middle of the day. Now, the time of year when most people observe this phenomenon is summer; which is also the best time for sea breezes. And the sea breeze usually starts to blow around late morning to lunch time. So low tide happens to coincide with a change in wind direction, but there is no cause-and-effect relationship between the wind and the tide.

As you can imagine, there are many more examples, some more absurd than others. I’ll be looking at a few more surf-related ones in upcoming articles. And part 2 examining whether winter or summer waves are heavier, coming soon.