Why is the water so cold in the summer? Part II
We've all felt it; wind can make or break a session. An offshore dawn patrol is a completely different experience than an afternoon onshore one. But wind does way more than just mess with the surface of the water. It can actually drive massive changes in water temperature.
You might be wondering, "How can wind change water temperature?" Well, it's all about movement, both of the air and the water. And here's where things get a bit wonky - the water moves in a completely different direction than the wind.
Instead, thanks to something called the Coriolis effect, the water actually moves to the right of the wind direction in the Northern Hemisphere.
Think of it like this: Imagine you're on a giant merry-go-round (that's Earth) and you're trying to roll a ball (that's the water) to your friend. You aim straight, but by the time the ball gets there, your friend has moved! The ball looks like it curved, but really, the merry-go-round just kept spinning. That's basically what's happening with wind and water, but on a much bigger scale.
Picture a day with wind blowing from the north. You'd think the water would just move south, but no, it's actually heading a bit southwest. As we go deeper underwater, it gets even more interesting.
The wind doesn't just push the top layer of water. It's like a domino effect - each layer of water drags the one below it, but each one gets pushed a little more to the west. Scientists call this the Ekman spiral, but you can think of it as the ocean doing a slow, underwater twist.
When that wind from the north pushes surface water out to sea, something's got to fill that space. And what fills it is unfortunately water cold enough to make a friend of mine crave a lukewarm beer. This is what scientists call "upwelling," but you can just think of it as the ocean's version of a cold front moving in.
Now, you might think this wind-driven temperature change is a summer-only thing, but that's not quite true. It happens year-round, but we notice it more in summer because that's when we're expecting warm water. In winter, when the water's already cold, a few extra degrees doesn't make much difference to our already numb toes
.What does all this mean for your next surf? Well, if the wind's been blowing from the north for a few hours or even days, don't be surprised if the water is frigid. But even if the wind isn't blowing, internal waves can still sneak in and chill things down when you least expect it. Combine them with wind-driven upwelling, and you've got a recipe for some seriously unpredictable water temperatures.
So next time you're checking the forecast before a session, don't just look at the wave height and period. Pay attention to the wind direction and speed too. It might just save you from an unexpectedly chilly surprise when you paddle out.
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