Significance of the Oceans
The Earth’s oceans play an important role in maintaining the world as we know it. Indeed,
the ocean is largely responsible for keeping the temperatures on Earth fairly steady. It may
get pretty cold where you live in the wintertime. Some places on Earth get as cold as -70oC.
Some places get as hot as 55oC. This is a range of 125oC. But compare that to the surface
temperature on Mercury: it ranges from -180oC to 430oC, a range of 610oC. Mercury has
neither an atmosphere nor an ocean to buffer temperature changes so it gets both extremely
hot and very cold.
On Earth, the oceans absorb heat energy from the Sun. Then the ocean currents move
the energy from areas of hot water to areas of cold water, and vice versa. Not only does
ocean circulation keep the water temperature moderate, but it also affects the temperature
of the air. If you examine land temperatures on the Earth, you will notice that the more
extreme temperatures occur in the middle of continents, whereas temperatures near the
water tend to be more moderate. This is because water retains heat longer than land.
Summer temperatures will therefore not be as hot, and winter temperatures won’t be as
cold, because the water takes a long time to heat up or cool down. If we didn’t have the
oceans, the temperature range would be much greater, and humans could not live in those
harsh conditions.
The ocean is home to an enormous amount of life. This includes many kinds of microscopic
life, plants and algae, invertebrates like sea stars and jellyfish, fish, reptiles, and marine
mammals. The many different creatures of the ocean form a vast and complicated food web,
that actually makes up the majority of all biomass on Earth. (Biomassis the total weight
of living organisms in a particular area.) We depend on the ocean as a source of food and
even the oxygen created by marine plants. Scientists are still discovering new creatures and
features of the oceans, as well as learning more about marine ecosystems (Figure14.3).
Finally, the ocean provides the starting point for the Earth’s water cycle. Most of the water
that evaporates into the atmosphere initially comes from the ocean. This water, in turn, falls
on land in the form of precipitation. It creates snow and ice, streams and ponds, without
whichpeoplewouldhavelittle freshwater. Aworldwithoutoceanswouldbea worldwithout
you and me.
Composition of Ocean Water
Water has oftentimes been referred to as the “universal solvent”, because many things can
dissolve in water (Figure14.4). Many things like salts, sugars, acids, bases, and other
organic molecules can be dissolved in water. Pollution of ocean water is a major problem in
some areas because many toxic substances easily mix with water.
Perhaps the most important substance dissolved in the ocean is salt. Everyone knows that
ocean water tastes salty. That salt comes from mineral deposits that find their way to the