Myths in Surfing: Are Cold Water Waves Heavier? Part II

Tony Butt

by on

Updated 31d ago

Ed's note: Last week, we asked the question, are cold water waves heavier? The internal MSW HQ debate raged. The comments on that piece were dashed with opinion. Go HERE to see. And now, we're going to take the great debate just a touch further...

Do cold, winter swells really pack more punch than warm, summer ones, or does it just seem that way?

While summer swells seem to be softer and lighter, winter ones are gnarlier and thicker, with denser, darker water and longer, scarier hold-downs. Wiping out in warm, summer surf can almost be a pleasant experience, whereas wiping out in big, icy, winter surf can be torturous.

Just ask Mo here about the brutality of cold water wipeouts.

So, are the waves really more powerful or is it just the effect of the cold water on our bodies, and on our minds? Most people agree that cold, winter swells seem to pack more punch that warm summer ones, even on the same beach with the same sized waves, but the reasons why are not so clear. I asked a few people what they thought about it:

“Winter waves are heavier because in cold water, the molecules are close together, thus making the water denser, though not much. In hot water, the molecules get so hot that they move faster, making them further apart and less dense.”

“Personally I think it's got more to do with were the swell has travelled from.”

“The cold seems to suck the air out of your lungs when you get smashed, so I reckon a cold water hiding hurts more”

Let’s take the first quote above – the fact that cold water is denser than warm water, therefore the waves really are heavier when they break on your head. As a simple example, let’s assume that the water temperature is 10°C in winter and 20°C in summer. The density of seawater at 10°C is about 0.2 per cent more than at 20°C; therefore the same volume of water will weigh about 0.2 per cent more. I don’t know how much the lip of a ten-foot wave weighs, but let’s assume it weighs somewhere in the region of a tonne. That lip falling on your head in winter will weigh two kilograms more than it would in the summer. Is that enough to notice the difference?

Russell Bierke at Mully - that thing on your head is gonna leave a mark or two.

Russell Bierke at Mully - that thing on your head is gonna leave a mark or two.

© 2021 - Tim Borrow.

The second quote suggests that winter swells are more powerful because they come from further away. This is very interesting. If you are lucky enough to get a ten-foot swell in the summer, it will most likely have come from a relatively weak low near the coast, meaning shorter periods and slower waves. On the other hand, the same size swell in the winter might have come from a more powerful storm much further away, meaning longer periods and faster, more powerful waves.

That idea works well for some places, but not for others. For example, what about places like Cape Town, South Africa, where the water can be 9°C in summer when you are surfing relatively weak five-foot beachbreaks, but 18°C in winter when you are surfing solid 20-foot Dungeons?

Maybe, like the third quote above, what really makes winter waves heavier is the effect the cold water has on the human body. This is logical. Even with a good wetsuit you can still feel the difference, especially if water seeps in somewhere or when the cold water hits your face. Water conducts heat away from your body 32 times quicker than air, and the body loses about half its heat through the head.

Therefore, a cold water hold-down will probably seem to last longer than a warm water one, with every painful second feeling like ten. When you eventually surface, you might feel disorientated and drained of energy, and the last thing you want is another wave on the head.

Finally, the psychological side of things could also be really important. Your own brain’s perception of the winter environment can make the whole surfing experience seem darker, heavier and more serious. For many of us, summer means blue water, warm weather and fun waves; but winter means ominous dark-green water, distant line-ups and unexpected clean-up sets. All this gets the adrenaline pumping before you even enter the water, let alone catch a wave or get drilled by a set.

Cover shot: Nazare by Helio Antonio.