How Salty Is the Ocean?
In general, the salinity (saltiness) of the ocean is 3.5 percent by volume. A gallon of seawater contains about a quarter of a pound of salt. Because waves and ocean currents keep the oceans pretty well stirred, it would seem that seawater ought to be the same throughout all the oceans.
It is – almost. In shallow seas and bays, evaporation leaves seawater with extra salt. Along seashores near the mouths of rivers, seawater is diluted with fresh water so that it is less salty. This happens also in the Arctic and Antarctic Oceans due to melting ice.
The ocean is made up of salt water, which is a combination of fresh water, plus minerals collectively called “salts.” These salts aren’t just sodium and chloride (the elements that make up our table salt), but other minerals such as calcium, magnesium, and potassium, among others.
These salts get into the ocean through several complex processes, including coming from rocks on land, volcanic eruptions, wind and hydrothermal vents.
How Much Salt Is in the Ocean?
According to the U.S. Geological Survey, there is enough salt in the ocean so that if you removed it and spread it evenly over the Earth’s surface, it would be a layer about 500 feet thick.