The 4 differences between sea and ocean, explained

Water (H2O) in its liquid form is the most present fluid in the world, since it represents 525 million cubic kilometers of water, or what is the same, 70% of the earth's surface.

Interestingly, the amount of water present in the planet's crust has neither increased nor decreased in the last 2 billion years: each of these molecules is transformed and is part of the biogeochemical cycles of ecosystems, but not disappears. Of all this percentage of terrestrial water, 20% passes underground or is part of atmospheric gases.

Over a 100-year period, an H2O molecule spends 98% of its time navigating the oceans, 20 months in the form of ice, 2 weeks in lakes and rivers and less than 7 days in the form of atmospheric gas. This entire hydrological cycle is outlined without taking into account that water also passes through the body of organisms, since we must not forget that 60% of an adult human being is this fluid.

These data are fascinating when put into perspective, since they show that a water molecule performs a vertiginous travel in each phase of the hydrological cycle, traveling distances that a human being cannot even conceive. This interesting train of thought leads us to a basic question, but difficult to solve:

What are the differences between sea and ocean?

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The 4 differences between the sea and the ocean

Many times, when we find terminological conflicts in the Spanish language, we can ask ourselves what is its meaning in English and other languages. In this case, the word Ocean refers to the ocean in English, while the sea is called sea. In both languages ​​this dichotomy occurs, so some scientific and substantial differences must exist between the two terms. We explore them below.

1. The seas are smaller than the oceans

The Royal Spanish Academy of Language (RAE) defines the sea as the mass of salty water that covers most of it of the earth's surface, each of the parts into which the sea or a lake of a certain extension. On the other hand, this same organism argues that the ocean is a sea of ​​great extension that separates two or more continents.

With these definitions more linguistic than geological, the question is not resolved. However, the National Ocean Service (NOAA) gives us a much more convincing answer: seas are smaller than oceans, and are generally conceived as the point of connection between land (beach) and the deep ocean. The seas are typically partially bordered by land at their limits.

Take the Mediterranean Sea as an example. This sea (not ocean) is enclosed between masses of continental land, and it only communicates with the outside thanks to the Strait of Gibraltar. On the other hand, it is surrounded by Europe, Africa and Asia. Beyond its geographical location, it should be noted that the Mediterranean Sea is divided into other sub-seas, among which are the Mar Menor, Mar Chica, Libyan Sea and Levantine Sea (from 15 totals).

2. There are many more seas than oceans

Although it is due to its smaller size, it is not difficult for us to deduce that, in effect, on Earth there will be more seas than oceans. According to the International Hydrographic Organization (IHO) there are a total of 60 seas, no more no less. Some of them are sure to be familiar to you: the Baltic, the Caribbean, the Mediterranean (already named), the Black, the Red, or the Andaman, among others.

On the other hand, we can only cite 5 oceans in the entire earth's surface. We name them and tell you some of their characteristics in the following list:

• Antarctic Glacier: its adjacent continent is Antarctica and covers 20,327,000 square kilometers. It has a depth of 3,270 meters.
• Arctic Glacier: it is adjacent to North America, Asia and Europe. It occupies 14,056,000 square kilometers and has an average depth of 1,205 meters.
• Atlantic: it is in contact with America, Europe and Africa. It is 106,500,000 square kilometers long and 3,646 meters deep.
• Indian: borders Africa, Asia and Oceania. It occupies an area of ​​68,556,000 square kilometers and has an average depth of 3,741 meters.
• Pacific: the continents adjacent to this ocean are Asia, America and Oceania. It has an area of ​​155,557,000 square kilometers and 4,280 meters deep.

The same body cited above estimates that, in these oceans, a total of 1,332 million cubic kilometers of water can be calculated. Summing up this point, there are 12 times more seas than oceans in the world, but the oceans are much more vast and extensive.

3. There are seas that are lakes

It may sound counterintuitive, but there are certain bodies of water enclosed in continental land that are called seas. This does not happen in any case with the oceans: we remember that there are only 5 and they collect most of the water from the earth's crust.

Some examples of this curious conflict at the nomenclature level are the Dead Sea, the Caspian Sea and the Aral Sea. For example, the Dead Sea (which borders Israel, the West Bank, and Jordan) is a saltwater lake that is 605 square kilometers long. It is famous for how easy it is to float when swimming in it (due to its very high salinity), but it also has a very special black mud, which stands out for its pharmacological properties.

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4. Different climatic conditions and changes in biodiversity

Due to its depth and extension, the oceans present much colder waters, with about 4 degrees of average temperature. The living beings that inhabit these demanding places have developed different strategies to maintain heat, despite being unable to generate it at a metabolic level.

For example, the leatherback turtle (Dermochelys coriacea), a reptile that is often classified as "cold-blooded", maintains its body 8 degrees above ocean water temperatures, due to thermogenesis produced by its movement muscular.

The oceans are very demanding ecosystems at a biological level, since the living beings that live in them do not have the funds at their disposal and the light does not reach them, so the food chain is severely limited (as there are no plants or algae available). As you can imagine, in the seas things is very different, since the solar incidence (depending on the depth) makes more appearance and the temperatures can be a little higher.

Due to this, the fauna and flora in the seas is much more overwhelming than that of the oceans, since there are algae, invertebrates, fish, mammals (and even birds) that form the trophic chains based on solar radiation and photosynthesis by the algae. The areas where life proliferates the most are hemipelagic, that is, they are found on continental shelves. This is where most of the marine biodiversity takes place.

The oceanic water block can be divided into the pelagic (light comes), mesopelagic, bathyal and abyssal zone. Due to the lack of direct contact with other land sources, life is much more scarce here.

Resume

As you may have seen, the main difference between a sea and an ocean is always the extent and location. A sea (generally) is shallower, covers less surface area and is surrounded in some of its limits by continental masses. On the other hand, the oceans are 5 immeasurable, deep bodies of water, with abyssal levels and the capacity to house most of the water present on the Earth's surface.

In other words, there are only 5 oceans, but each of the 60 seas mentioned are circumscribed around them. The seas act as bridges between the oceans and the Earth, but both are conceived within the general concept of intercontinental land masses of water.