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 in other words, 70% of the Earth’s surface.
Curiously, the amount of water present in the planet’s crust has not increased or decreased in the last 2 billion years: each of these molecules is transformed and is part of the biogeochemical cycles of ecosystems, but it does not disappear. Of this entire percentage of terrestrial water, 20% passes underground or is part of atmospheric gases.
Over a period of 100 years, a H2O molecule spends 98% of its time sailing 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 if put into perspective, since they show that a water molecule makes a dizzying journey in each phase of the hydrological cycle, traveling distances that a human being cannot even conceive. This very interesting train of thought leads us to a basic question, but difficult to resolve: What are the differences between the sea and the ocean?
Many times, when we find terminological conflicts in the Spanish language, we wonder what their meaning is in English and other languages. In this case, the word Ocean refers to the ocean in English, while the sea is called sea. This dichotomy occurs in both languages, so some scientific and substantial differences must exist between both terms. Next, we explore them.
The Royal Spanish Academy of Language (RAE) defines the sea as the mass of salt water that covers most of the earth’s surface, each of the parts into which the sea or a lake of a certain size is considered divided. On the other hand, this same organization argues that the ocean is a large sea that separates two or more continents.
With these definitions that are more linguistic than geological, the question is not resolved. In any case, the National Ocean Service (NOAA) gives us a much more convincing answer: Seas are smaller than oceans, and are generally conceived as the connection point between the land (beach) and the deep ocean Typically, seas are partially bordered by land at their boundaries.
Let’s take the Mediterranean Sea as an example. This sea (not ocean) is enclosed between continental land masses, and is only communicated with the outside world 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 the Mar Menor, Mar Chica, Libyan Sea and Levantine Sea stand out (out of 15 total).
2. There are many more seas than oceans
Although it is due to its smaller area, it is not difficult for us to deduce that, in fact, there will be more seas than oceans on Earth. According to the International Hydrographic Organization (IHO) there are a total of 60 seas, no more no less. Some of them will surely sound 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 name 5 oceans on the entire Earth’s surface We name them and tell you some of their characteristics in the following list:
The same organization mentioned above estimates that, in these oceans, a total of 1,332 million cubic kilometers of water can be calculated. Summarizing this point, there are 12 times more seas than oceans in the world, but the oceans are much vaster and more extensive.
3. There are seas that are lakes
It may sound counterintuitive, but There are certain masses 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.
4. Different climatic conditions and changes in biodiversity
Due to their depth and extension, the oceans have much colder waters, with an average temperature of about 4 degrees. The living beings that inhabit these demanding places have developed different strategies to maintain heat, despite being incapable of generating it at a metabolic level.
For example, the leatherback turtle (Dermochelys coriacea), a reptile that is usually classified as “cold-blooded,” maintains its body 8 degrees above the temperatures of ocean waters, due to the thermogenesis produced by its muscular movement.
The oceans are very demanding ecosystems on a biological level, since the living beings that live in them do not have the funds at their disposal and light does not reach them, so the food chain is greatly limited (as there are no plants or algae available). As you can imagine, in the seas things are very different, since solar incidence (depending on the depth) is more present and 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 food chains based on solar radiation and photosynthesis by part of 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 develops.
The block of ocean water can be divided into the pelagic (light reaches), mesopelagic, bathyal and abyssal zone. Due to the lack of direct contact with other land sources, life is much scarcer here.
Summary
As you may have seen, the main difference between a sea and an ocean is always the extension and location. A sea (generally) is shallower, covers less surface area and is surrounded on some of its limits by continental masses. On the other hand, the oceans are 5 vast, deep masses of water, with abyssal levels and the capacity to house the majority 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 terrestrial water masses.
