Ocean

The ocean is a body of water that makes up much of the hydrosphere of a celestial body. On Earth, an ocean is one of the main conventional divisions of the World Ocean, and "separates two or more continents." Oceans occupy most of the planet's surface.

Seawater covers approximately 361,000,000 km² and is typically divided into several major oceans and smaller seas, with the ocean as a whole covering approximately 71% of the Earth's surface and 90% of the biosphere The world ocean contains 97% of Earth's water, and oceanographers have claimed that less than 20% of the oceans have been mapped and less than 10% with modern sonar methods. The total volume is approximately 1.35 billion. cubic kilometers (320 million cubic miles) with an average depth of nearly 3,700 m.

Because the world ocean is the major component of Earth's hydrosphere, it is an integral part of life, is part of the carbon cycle, and influences climate and weather patterns. The ocean is the habitat of 230,000 known species, but because much of it is unexplored, the number of species in the ocean is much higher, possibly more than two million. The origin of the terrestrial oceans is unknown; a considerable amount of water would have been in the material that formed the Earth. Water molecules would have more easily escaped Earth's gravity when the Earth was less massive during its formation due to atmospheric escape. The oceans are believed to have formed in the Hadean eon and may have been the cause of the emergence of life.

The oceans present numerous environmental problems, including marine pollution, overfishing, ocean acidification, and other effects of climate change on the oceans.

Alien oceans can be made of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are Titan's lakes, although there is evidence of oceans elsewhere in the Solar System.

They are classified into three major ones: Atlantic, Indian and Pacific; and two minor ones: Arctic and Antarctic, partially delimited by the shape of the continents and archipelagos.

The Pacific and Atlantic oceans are often divided into North and South, depending on whether they are in the Northern or Southern Hemisphere: North Atlantic and South Atlantic, and North Pacific and South Pacific.

Terminology

The Atlantic Ocean, a component of the system, constitutes 23% of the "global ocean".

View of the surface of the Atlantic Ocean.

The phrases "the ocean" or "the sea" used without specification refer to the interconnected mass of salt water that covers most of the Earth's surface. It includes the Atlantic, Pacific, Indian, Antarctic, and Arctic. As a general term, "the ocean" is mostly interchangeable with "the sea" in American English, but not British English. Strictly speaking, a sea is a body of water (usually a division of the world ocean) partially or wholly bounded by land. The word "sea" it can also be used for many specific, much smaller bodies of marine water, such as the North Sea or the Red Sea. There is no sharp distinction between seas and oceans, although seas are generally smaller, and are often partially (as marginal seas) or wholly (as inland seas) bordered by land.

World Ocean

The global, interconnected body of salt water is sometimes called the "world ocean" or global ocean. The concept of a continuous body of water with relatively free exchange between its parts is of general importance to oceanography. The contemporary concept of World Ocean was coined at the turn of the century. XX by Russian oceanographer Yuly Shokalsky to refer to the continuous ocean that covers and surrounds most of the Earth. Tectonics Plate formation, postglacial rebound, and sea level rise continually change the coastline and structure of the global ocean. That being said, a global ocean has existed in one form or another on Earth for millions of years.

Etymology

The word ocean comes from the character of classical antiquity, Oceanus from the Greek Ὠκεανός Ōkeanós, pronounced /ɔːkeanós/, the greatest of the Titans in classical Greek mythology, believed by the ancient Greeks and Romans to be the divine personification of a huge river that encircled the world.

The concept of Ōkeanós has an Indo-European connection. The Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, which captured cows/rivers. Related to this notion, the Okeanos is depicted with a dragon's tail on some early Greek vases.

General characteristics

Oceans cover 71% of the Earth's surface, with the Pacific being the largest.

The depth of the ocean is variable depending on the areas of the oceanic relief, but it is shallow compared to its surface. It is estimated that the average depth is approximately 3900 meters. The deepest part is in the Mariana Trench, reaching a depth of 11,034 m.

The following table summarizes some characteristics of the 5 oceans.

In the oceans there is a superficial layer of warm water (12 °C to 30 °C) that reaches a variable depth depending on the area, from a few tens of meters to 50 or 100 m. Below this layer, the water has temperatures between 5 °C and –1 °C. It is called a thermocline at the boundary between the two layers. The water is warmer in the temperate, equatorial zones and colder near the poles. And, also, warmer in summer and colder in winter.

Origin

Until recently, they were thought to have formed about 4 billion years ago, after a period of intense volcanic activity, when the temperature of the planet's surface cooled to a point where water was in a liquid state. Although the controversy continues, a study by the scientist Francis Albarede, from the French National Center for Scientific Research (CNRS), published in the journal Nature estimates that its origin lies in the collision of giant asteroids covered of ice that collided with the Earth between 80 and 130 million years after the formation of the planet.

It is believed that water, being a universal substance, has been around since the planet was being formed and then it came in greater quantity from the asteroid belt, and not from the Oort cloud as previously believed, since in In this last area there is a higher concentration of deuterium (forming heavy water) compared to what exists on earth. This fact was confirmed in direct analyzes of comets from the Oort cloud, such as the last one carried out by the Rosetta probe.

Sea water

Temperature profile (Grades Celsius) regarding the depth (meters) of oceanic water, typical of medium and low latitudes. Thermoclin are layers of water where its temperature changes rapidly with depth.

It contains solid substances in solution, the most abundant being sodium and chlorine which, in their solid form, combine to form sodium chloride or common salt and, together with magnesium, calcium and potassium, constitute about 90% of the dissolved elements in seawater. There are also other elements but in minimal quantities.

Temperature

The water temperature of the oceans varies depending on a number of parameters, among which are: latitude; the presence of marine currents; the depth; etc

The Argo program has deployed more than 3,000 floats in the oceans to record the salinity and temperature of the ocean's surface layer. Each of the floats is scheduled to sink at a depth of 2,000 meters, and will drift at that depth for approximately 10 days. Subsequently, the float will emerge back to the surface continuously measuring the temperature and salinity. Once the float reaches the surface, the data is sent to a satellite, so that scientists and the public have access to this information about the state of the oceans within hours of data capture.

Water salinity

Evaporation of sea water.

The salinity depends on the amount of salts it contains. Approximately an average of 3.5% of the mass of water corresponds to substances in solution. If there is a lot of evaporation, a greater amount of water disappears, leaving dissolved substances, so salinity increases.

It is scarce in the polar regions, especially in the summer when the ice melts into the water. In seas like the Baltic, there is also little salinity.

It should be noted that in its great extension, the ocean presents each and every one of the existing natural chemical elements, either by runoff from the continents or existing reserves in it.

Most of the water on Earth, 94%, is found in the oceans, from which more pure water evaporates than returns as precipitation. The volume of water in the oceans remains unchanged since they receive water through rivers.

The water in the oceans is also salty due to the eruption of submarine volcanoes. Volcanic rock provides salts.

Composition

Practically all the elements exist dissolved in water, in a minute quantity, but since the oceans have such a colossal volume, they constitute inexhaustible reserves of raw materials, although, with the exception of sodium chloride (salt common), its extraction offers little profitability. These elements, in descending order, are the following (in brackets the content in grams per liter): 1st Chlorine (19); 2nd Sodium (10.5); 3rd Magnesium (1.35); 4th Sulfur (0.885); 5th Calcium (0.400); 6th Potassium (0.380); 7th Bromine (0.065);... 39th Silver (0.000 000 3);... 57th Gold (0.000 000 004).

Color of water

A common way of thinking is that the water in the oceans is blue mainly due to the reflection of the blue color of the sky. Actually water itself has a slight blue color when stored in large quantities. Reflection from the sky contributes to the blue appearance of the water but is not the main reason. The origin is due to the absorption by the water molecules of the "red" photons coming from the incident light, being one of the few cases in nature produced by vibration and electronic dynamics.

The waves

Seawater is rarely still, moving in waves, tides, or currents. The waves are due to the wind blowing on the surface. The height of a wave is given by the speed of the wind, the period in which it has blown and the distance that the wave has traveled. The highest recorded wave was 64 meters^{[citation needed]}, but they are generally much lower. They play a fundamental role in the formation of the coasts.

Tsunamis

Tsunami who hit Malé in the Maldives on 26 December 2004.

They are a type of waves whose origin is earthquakes, tidal waves or the eruption of submarine volcanoes. They displace large amounts of water very quickly, modifying the surface of the sea and creating waves that move away from the area of the earthquake or the volcano. They get to travel at 750 km/h. In the open sea they cause little damage, since they are low in height (less than 1 meter). In shallow water their speed decreases but their height increases to 10 meters or more and they usually cause catastrophic damage when they reach the coast.

Tides

Tides are caused by the gravitational attraction exerted by the Moon and the Sun. The attraction is greater on the side of the Earth that faces the Moon, causing a high tide or high tide. The Sun, being at a greater distance, produces a lesser effect than the Moon. These can become causes of flooding in coastal towns.

Spring Tides

Spring tides are called the moments in which the maximum attraction occurs, and they are formed when the Moon, the Sun and the Earth are on the same line, that is, during the Full Moon or Moon phases New, so they occur every 14 days, that is, twice a month.

Nap Tides

They are less intense tides that occur when the Moon and the Sun form a right angle with the Earth, because the attractions of both, being in opposite directions, subtract from each other instead of adding. Of course, despite its smaller size, the attraction of the Moon is greater because it is closer. These tides occur in the Waxing Quarter and Waning Quarter phases.

Tidal range

It is the difference between the high and low tide levels, which varies according to the place, from less than 1 meter in the Mediterranean Sea and the Gulf of Mexico, to 14.5 meters in the Bay of Fundy, on the eastern coast from Canada.

Ocean currents

	Perpetual Ocean Visualization of marine currents between 2005 and 2007, by NASA.
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Currents near the surface of the oceans are driven by the winds, which carry them with them. They move at a slower speed than the wind and do not have the same direction as them, since they are twisted to one side due to the effect of the Earth's rotation or Coriolis force. They change direction to the right of their path in the northern hemisphere and to the left in the southern hemisphere.

Currents have an important influence on the climate, for example, the Gulf Stream, which originates in the Caribbean, provides the northwest of Europe with milder winters.

The 28 ocean currents are:

Ocean gyres

The five biggest twists, in the Indian, Pacific and Atlantic oceans.

In oceanography it is a large system of rotating ocean currents, particularly those associated with large wind movements. The spins are caused by the Coriolis effect; along the planetary vortex with horizontal and vertical friction, which determines the circulation pattern for the wind (torque) loop.

There are five great gyres, two in the north and two in the south for the Pacific and Atlantic Oceans, respectively, and one for the Indian Ocean. Others also exist: tropical gyres, subtropical gyres, and subpolar gyres.

It has been proven that in the gyres of the Atlantic and North Pacific there is a large accumulation of marine debris floating adrift. They are known as the Great North Pacific Garbage Patch and the North Atlantic Garbage Patch.

Morphology of the seabed

Profile showing the continental margin with its three parts: the continental shelf, the continental shelf and the continental shelf (or edge).

Section of an ocean basin, showing the various accidents.

Age of the seabed.

The main oceanic features are:

• The continental margin, which is the portion of the seabed that is closest to firm land. It is divided into:

• Continental shelf or submarine platform: is the least deep, reaches 200 m deep, being quite flat. The water that covers it usually contains marine life in abundance and most fishing is done in this area. Here is the fourth part of the world's oil and gas production, coming from the rocks below these platforms.
• Continental talud, scarpadura or continental scarp. The size range varies depending on the ocean in which it is located. It has a steeper slope than the previous one and is between 200 to 3000 meters deep, approximately.
• Continental edge. It is in the final part of the talud and would mark the limit with ocean funds.

• Ocean Dorsales. They are submarine, vast and steep mountain chains, usually located in the center of the oceans. On average they measure 1000 km wide with a height of 3000 m. They form a more or less connected system of 80 000 km long, receiving different names, for example, dorsal Mesoatlantica, dorsal of Reykjanes or dorsal of the Eastern Pacific.
• Abysmal plains. They form between the oceanic dorsals and the continental margins. They are very flat and uniform areas, around 4000 m deep. They account for approximately 40% of the ocean floor.
• Underwater volcanoes
• Oceanic or abyssal pits. They are the deepest parts of the oceans, with an average of 7000 to 8000 m deep, which can measure thousands of kilometers long. La fosa de Las Marianas has the highest depth of the planet with more than 11 000 m below sea level.

Pollution

Earth's oceans also play a vital role in cleaning up the atmosphere, and some human activities can severely alter them. The oceans absorb enormous amounts of carbon dioxide. In turn, phytoplankton absorb carbon dioxide and release oxygen. George Small explains the importance of this life cycle: "70% of the oxygen added to the atmosphere each year comes from plankton in the sea." However, some scientists warn that phytoplankton could seriously decline due to depletion of ozone in the atmosphere, for which man is believed to be responsible.

Some countries agree to limit the waste they allow to be dumped into the sea, others refuse to do so. The famous ocean explorer Jacques Cousteau warned: "We have to save the oceans if we want to save humanity."

The concentration of fish in small areas of the ocean and its scarcity in other parts is significant. As William Ricker, a fisheries biologist, warned: "The sea is not an unlimited reservoir of food energy." And underwater explorer Jacques Cousteau also warned, returning from a global underwater exploration, that life in the oceans has declined by 40% since 1950 due to overfishing and pollution.

Swiss marine scientist Jacques Piccard predicted that at the current rate of pollution, the world's oceans would be devoid of life in 25 years. He said that because of its shallowness, the Baltic would be the first to die. Then the Adriatic and the Mediterranean would die, both of which do not have currents strong enough to carry the pollution. Also, French underwater explorer Jacques Cousteau said that the destruction of the oceans is already 20-30% done. He predicted "the end of everything in 30 to 50 years unless immediate action is taken." Part of this pollution is due to the fact that society has had for centuries the mistaken concept that these have an inexhaustible capacity to receive waste.

The oceans cover 71% of the earth's surface, they are being polluted very frequently by human activity and the overexploitation of natural resources. Around 5 garbage islands have been located with a huge amount of waste, these are formed due to marine currents (natural eddies), the size of the most affected area is 3.4 million km², which is located in the North Pacific Ocean. The most polluting countries are China, Indonesia, the Philippines, Thailand and Vietnam, these countries discharge the largest amount of plastic waste into the sea than the rest of the countries in the world combined.