Why the Ocean Changes Color, Depending on Your Location

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There are few things that attracts human beings the way the ocean does. We’re not natural water-going beings, and yet, the lure of the sea’s vastness, the calming sound of its waves, has drawn us in since the beginning of time.

If you’re someone who has gone out of their way to visit the ocean whenever and wherever you’re in the vicinity, you might have noticed that it’s not always the same color.

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It makes sense, to some extent, that the ocean is an ever-changing beauty, and you probably guess that it has something to do with the depth in certain regions, but is there more to it?

Hold on – let’s find out together!

First, let’s dispel the notion that the water is – or is even supposed to be – blue. NASA oceanographer Gene Carl Feldman explains:

“The water of the ocean is not blue, it’s clear.

The color of the ocean surface for the most part is based on depth, what’s in it and what’s below it.”

Basically, if a body of water is deep enough that light can’t reflect off the bottom, it appears blue. When the sun’s rays strike the ocean, they interact with water molecules and can be either absorbed or scattered. Light of shorter wavelengths – which looks to the human eye blue or green – is most likely to hit water molecules and scatter.

The depth of the water, as well as the composition of the ocean bottom, will affect whether we see the dusky, dark blue of large parts of the Atlantic, or a sapphire-blue as in the tropics, says Feldman.

“In Greece, the water is this beautiful turquoise color because the bottom is either white sand or white rocks.

What happens is the light comes down and blue light gets down, hits the bottom and then reflects back up so you make this beautiful light blue color in the water.”

Complicating matters is the fact that the ocean isn’t empty – it’s full of small plant and animal life, along with sediment or other, man-made, contaminants.

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Feldman studies images of the ocean’s surface taken by satellite, and can analyze the color patterns to assess where sediment and runoff are an issue (the water will appear brown) or where phytoplankton, a microscopic plant, turns the water green.

Phytoplankton use chlorophyll to convert water and carbon dioxide into organic compounds, generating about 50% of the oxygen on the planet. They give ocean water a green tint most of the time, though they can also cause us to see yellow or reddish brown in some situations.

Feldman says green water should make us smid
As with everything in this world, balance is key – and both a decrease or increase in phytoplankton is not a good thing. It’s one more sign that our planet’s climate is out of whack.

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In the ocean’s least-touched, least-polluted sector – in the water off the coast of Easter Island – the water is deep and remarkably clear. It appears to the naked eye a pure, deep indigo.

“The light just keeps going down, down, down; there’s nothing that bounces it back.

Here is the deepest blue you’ll ever see.”

Just one more reason to love the ocean, y’all.

And if you do, with the depths of your heart, it’s long past the time to join in the fight to save it.