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Mean sea-surface salinity. Grey shaded areas (land) exceed 36 psu (practical salinity units).
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Image courtesy of NOAA

Salinity

Almost 3/4 of the Earth is covered with water. Almost all of that water is in the oceans. Have you ever been swimming in the ocean? If you have and you accidentally got water in your mouth, you know the ocean tastes really salty!

Ocean water is about 3.5% salt. That may seem not seem like a lot, but it is! If the oceans dried up completely, enough salt would be left behind to build a 180-mile-tall, one- mile-thick wall around the equator! Almost all of that salt would be ordinary table salt.

Salinity is a measure of how much salt is in water. Sometimes, scientists measure salinity in parts per thousand (ppt). The average salinity of the ocean is 35 ppt. That's the same as saying the ocean water is 3.5% salt.

Life in the oceans likes to live in salty water. But, most creatures that live in the ocean could not live in fresh water. When the salty waters of the ocean meet fresh water, an estuary is formed. This is a special place where some creatures have learned to adapt to a mixture of fresh water and salt water. For more information on salinity, please use the links below...

Last modified August 30, 2001 by Jennifer Bergman.

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The Spring 2010 issue of The Earth Scientist, focuses on the ocean, including articles on polar research, coral reefs, ocean acidification, and climate. Includes a gorgeous full color poster!

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