The Five Oceans

The Blue Planet is how the Earth is best described. With the abundance of water, it looks beautifully blue from outer space. No other planet in this universe has the same amount of water as that of the Earth. It is what makes our world unique to other planets. The ocean is from Ancient Greek  Ὠκεανός or Okeanos – believed by the ancient Greeks and Romans to be the divine personification of the sea, an enormous river encircling the world. The ocean is every so often interchanged with “sea” in American English. By definition, the sea is a body of saline water (within the world ocean division) partly enclosed by land. “The Sea” also refers to the ocean.

The Earth’s hydrosphere is made up mostly of oceans but it also embodies other bodies of water like lakes, seas, rivers, and underground waters.

Names of the five oceans

Oceans are Earth’s major conventional divisions. By order, they are; Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. These bodies of water contain 97% of Earth’s water and less than 5% of it has been explored. Its total volume is approximately 1.35 billion cubic kilometers and an average depth of closely 3,700 meters.

Oceans, being the world’s principal component is integral to life. It shapes part of the carbon cycle and has a great impact on climate and weather patterns. It is the habitat of more or less 230,000 known species, however, since much of it remains unexplored, the number of species that exist in the ocean may be much larger – perhaps over a couple billion. The origin of Earth’s ocean is yet completely understood. There are several compatible hypotheses as to how these bodies accumulated Earth.

The five oceans, although generally described as separate bodies of water are still interconnected body of salt. Listed down in descending order by area and volume are the major oceanic divisions.

Sources: Encyclopedia of Earth,[19][20][21][22][26] International Hydrographic Organization,[23] Regional Oceanography: an Introduction (Tomczak, 2005),[24] Encyclopædia Britannica,[25] and the International Telecommunication Union.

Physical Properties

Less than 3% of the Earth’s hydrosphere is freshwater. The rest is salt water almost all of which is in the ocean. The world ocean is about 139.7 million square miles and covers nearly 70.9% of the Earth’s surface. Its volume is approximately 323.3 million cubic miles.

The ocean, as huge as it is does not have a constant temperature. Energy is imparted from sunlight throughout all summer, the ocean holds it in so that once winter comes, it can release the warmth back into the atmosphere according to their heat capacity. Its density as with other sea waters is nearly uniform at all latitudes. Surface density lessens a little by the equator which is a phenomenon due to tropical climates. Pycnocline is the sharp difference in density within the tropical regions.

Water’s bluish color is a fuse of a number of contributing agents. Dissolved organic matter and chlorophyll are prominent factors. Oceanographers and seafarers have claimed that the ocean emits an evident glow which extends for miles at night. This glow, as announced by scientists is most likely caused by bioluminescence.


The deepest point amongst all the oceans is the Marianas Trench, located in the Pacific Ocean. Only 5% of the total water surface has been explored and much remains to be learned from it. SONAR or Sound Navigation and Ranging is the technology that is very effective for studying and mapping the ocean. This technology uses sound waves to develop nautical charts and to check for underwater hazards.


Water Cycle plays a vital role in marine biology. Oceanic evaporation is the starting place of most rainfall. Ocean temperatures also establish climate and wind patterns that affect life on land and underwater. Life has evolved underwater earlier than it did on land. The diversity of life underwater is immense that it includes the smallest to the biggest creature there is – from bacteria (single-celled prokaryotes), archaea, algae (including organisms like Pyropia – or the edible Nori seaweed), plants (including seagrasses and mangroves), fungi, and animals. Most animal Phyla have species that inhabit the ocean such as sponges, corals, jellyfish, crustaceans, etc., Land animals have also tailored their living to the oceans, like seabirds, penguins, seagulls, and pelicans.


The Earth’s oceans have a salinity of about 3.5 percent or 35 parts per thousand. It means that for every liter of ocean water, there are 35 grams of salt dissolved in it. Halocline is the zone of rapid salinity increase with depth. When salt content increases, the temperature of maximum sea water density decreases. Salinity also affects ocean temperature whereas the freezing temperature of water decreases with salinity and boiling temperature of water increases with salinity. Many chemicals in the oceans make it salty. These chemicals get there from rivers carrying chemicals dissolved from rock and soil. Leading is sodium chloride or often just called salt.

Salinity also varies with the location. There are portions of the ocean where it hardly rains but constantly getting warm dry winds causing too much evaporation. Evaporation removes water and when water vapor rises, it leaves the salt behind thus, causing the salinity of the saltwater to increase on that point. Increased salinity causes water to become denser. The Mediterranean Sea in Europe has a very high salinity as there is more evaporation than there is rain.

Those parts of ocean that get lots of rain get freshwater added and dilutes seawater. As it does, it reduces salinity and makes the ocean less dense. The ocean around Antarctica has a low salinity due do thawed icebergs that add freshwater. The ice sheets that broke off that formed over land do not contain salt.

Economic Value

According to the WWF, our oceans are worth at least $24 trillion. Goods and services are done from and within coastal and marine environments amount to around $2.5 trillion each year. More than two-thirds of the oceans’ economic values rely on healthy condition. If there is too much habitat destruction, overfishing, pollution, and climate change, it imperils this economic engine and the livelihoods it supports.

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