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March 2, 2024 7 mins

The ocean can appear to be many different shades of blue (and green, and even violet) -- but all water is clear. Learn why in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/environmental/earth/oceanography/why-is-ocean-different-colors-different-places.htm

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Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Lauren vogelbaumb Here, someone gazing out at the ocean from
the coast of Maine might see deep, navy to midnight
blue water, very different hues than someone squinting at the
bright turquoise sea from a sunny beach on a Greek island.

(00:24):
So why is the ocean blue? And why does it
come in so many different shades? Before the article this
episode is based on how Stuff Work, spoke with NASA
oceanographer Jean Carl Feldman, who pointed out that, first of all, quote,
the water of the ocean is not blue, it's clear.
The color of the ocean's surface, for the most part,

(00:45):
is based on depth, what's in it and what's below it.
That's right. All water is clear by its nature. But
here's why it looks different in a glass versus from
a beach. A glass of water appears clear because light
passes through it with little to no obstruction. But if
a body of water is deep enough that light isn't

(01:06):
reflected off the bottom, it appears blue. Basic physics explains
why a visible light is made up of a spectrum
of different wavelengths The longer wavelengths appear to our eyes
as shades of red and orange, while the shorter ones
appear as blues and violets. When light strikes the ocean,
it interacts with water molecules and can be either absorbed

(01:28):
or scattered. If nothing is in the water except water molecules,
the longer red portions of the spectrum are absorbed by
the water. The shorter, zippier blue wavelengths are more likely
to hit something, including water and scatter, meaning they make
it back to our eyes, meaning the ocean appears blue.

(01:49):
Violet wavelengths are even shorter in zippier, but there are
fewer of them in sunlight, and our eyes perceive the
blue ones better at long distances, like near the horizon.
Another factor that we've actually talked about in a different
episode comes into play. A mountains appear blue in the
distance no matter what color they are up close, because

(02:10):
the air itself is made up of molecules that scatter
those zippy blue wavelengths of light, so the ocean far
out in the distance may look bluer than the water
near a beach. The depth of the water and what
the ocean floor is made of also influence this, A
Feldman explained in Grease, the water is this beautiful turquoise

(02:30):
color because the bottom is either white sand or white rocks.
What's happening here is that the light hits the shallow
sea floor and then bounces back up, projecting the beautiful
blue green color you see in the water. It's particularly
bright because some of those beaches have very little stuff
in the water, but the ocean is often teeming with

(02:53):
tiny planted animal life or fulfilled with suspended sediment or containinents.
Oceanographers monitor the ocean color as doctors read the vital
signs of their patients. The color seen on the ocean's
surface reflects what's going on in its vast depths pun intended.
A Feldman, who is based at the NASA Goddard Space

(03:13):
Flight Center in Maryland, studies images taken by the Sea
Viewing Wide Field of View Sensor satellite, which launched back
in nineteen ninety seven. From its orbit more than four
hundred miles or six hundred and fifty kilometers above Earth,
the satellite captures van go like swirls of the ocean's colors.
The patterns are not only mesmerizing, but they also show

(03:35):
where sediment and runoff may make the water appure a
muddy brown color, or where microscopic plants called phytoplankton collected
nutrient rich waters and tinting it green. Phytoplankton use chlorophyll,
which is a green pigment, to capture energy from the
sun to convert water in carbon dioxide into food to
fuel themselves. Through this process called photosynthesis, phytoplankton generate about

(03:59):
half of the oxygen we breathe. While most phytoplankton give
ocean water a green tint, some lend it a yellow, reddish,
or brown tint. Oceans with high concentrations of phytoplankton can
appear blue green to green, depending on the density. Greenish
water may not sound appealing, but as Feldman says, if

(04:19):
it weren't for phytoplankton, we wouldn't be here. Phytoplanktons serve
as the base of the ocean's food web because they're
the primary source of food for zooplankton, which are tiny
animals that are eaten by fish. The fish are then
eaten by bigger animals like whales and sharks. But when
oceans become polluted with runoff, the amount of phytoplankton can

(04:40):
escalate to unhealthy levels. Phytoplankton feed on the pollutants, flourish
and then die in huge numbers, sinking to the bottom
and decomposing in a process that depletes oxygen from the water,
which means larger animals can't survive there. On a map
on Feldman's office wall is a mark showing a spot

(05:01):
where there is little human interference and the ocean water
is perhaps the clearest and cleanest on the planet. In
this region, off the coast of Easter Island in the
Southeast Pacific Ocean, the water is deep and remarkably clear
due to its location in the middle of a giant
oceanic guyer a large circular current. Its central location means

(05:23):
there's minimal mixing of ocean layers, and sediment isn't pushed
up from the deep bottom. The purity of the water here,
coupled with its depth, make the ocean here appear a
deeper indigo than perhaps anywhere else. Feldman said, the light
just keeps going down, down, down, There's nothing that bounces aback.

(05:44):
Here is the deepest blue you'll ever see. That being said,
of course, light doesn't just keep going down into the
water forever. Eventually the water absorbs all of it and
nothing is left to bounce back up to the surface.
Band our eyes. Over half of all visible light is
absorbed within the first ten meters or thirty feet of

(06:06):
water at the ocean's surface. At one hundred meters or
three hundred feet, ninety nine percent of light will have
been absorbed. Even in very clear water. That's where you
get that deep indigo off Easter Island. All of the longer,
slower wavelengths have been absorbed, leaving only the darkest violet blue. However,

(06:26):
at about twice that depth, light never penetrates, and everything
that lives there lives in total darkness unless they create
their own light through by aluminescence. But that's a different episode.
Today's episode is based on the article why is the
ocean different colors in different places? On HowStuffWorks dot Com?

(06:49):
Written by Amanda Onion. Rain Stuff is production by Heart
Radio in partnership with how Stuffworks dot Com and is
produced by Tyler Klang. Four more podcasts fy Heart Radio,
visit the iHeartRadio app, Apple podcast Guests, or wherever you
listen to your favorite shows

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