Ocean vs sea: a story of conventions
You should know that the oceans and seas are defined by conventions decided by man, and not really on objective criteria. For example, the name “ocean” did not become official until the end of the 19th century, after Magellan sailed the Pacific Ocean and named it so in calm weather.
Note that the word “sea” comes from the Latin, mare et maris. The term “ocean” originates from the Greek word Ôkeanos, a marine deity who symbolized the water that surrounds the “disk” of the Earth. So, according to conventions, an ocean is referred to as a large expanse of salt water bordered by continents.
There are 5 oceans on the planet:
- Peaceful,
- Atlantic,
- In the event that,
- Arctic,
- Austral.
- A question of size
The first criterion that distinguishes the sea from the ocean is above all a story of expanse. The ocean is bigger! To give you an idea, the smallest ocean, the Arctic, is 14.09 million km². While the largest sea, the Arabian Sea, covers 3.6 million km2.
Borders or annexes seas
Among the seas, oceanographers distinguish two different types. First, the bordering seas, arranged along the contour of the oceans and closed by peninsulas, islands or shoals. The annex seas communicate with the ocean only by a strait and are surrounded by emerged lands.
This is the case of the Mediterranean and the Strait of Gibraltar. There are three seas that are totally closed: the Caspian Sea, the Aral Sea and the Dead Sea . Not to mention that some are squarely part of the oceans, like the Yellow Sea in the Pacific Ocean.
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Seas saltier than the oceans
Another criterion to take into account, the seas are much saltier than the ocean because of greater evaporation. For example, the salinity of the ocean averages around 35 grams / liter. In the Red Sea, this rises to 41 g / l. That’s 275 g / l for the Dead Sea! Exception which confirms the rule, for the Baltic Sea , it is between 5 and 10 g / l, which is fed by many rivers .
Depth and biological diversity
Depth is also taken into account. For example, the Norwegian Sea can reach 4000 meters. Even better, the Coral Sea, located between Australia and New Caledonia has its maximum point at 9,140 m. Nearby, the English Channel or the North Sea act as a puddle of water 200 meters deep … As for the ocean, almost half of its waters exceed 3,000 m deep. The Mariana Trench, with its 11,020 m depth, is the deepest point.
The oceans are larger, but it is in the seas that we find the greatest biological diversity. The Mediterranean Sea is therefore home to between 4 and 18% of the planet’s marine species, while it represents less than 1% of the surface of the world’s ocean. Small but sturdy!
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