EXPLORE the MYSTERIES of OCEANS

We explain what oceans are, which ones exist and their characteristics. Also, its dimensions, its environmental problems and more.

What are the oceans?

Oceans are large expanses of salt water that separate two or more continents.. They cover most of the Earth's surface (71%) and contain more than 1.3 trillion cubic kilometers of water, representing 97% of the planet's water supply.

There are five large oceans on Earth: the Pacific, the Atlantic, the Indian Ocean, the Antarctic Glacier and the Arctic Glacier. The sum of its surface reaches 361,000,000 km² and have an average depth of 3,900 meters. The deepest point is in the Mariana Trench, in the Pacific Ocean, with 10,992 meters under the water surface.

Life originated in the oceans and currently they are home to great biodiversity, from small single-celled organisms to large mammals such as the blue whale, the largest animal on the planet. Furthermore, the aquatic ecosystems that develop in the oceans are essential as sources of resources for human beings.

Oceans are a vital element of the water cycle and are essential for regulating the planet's climate. Likewise, they store a large amount of carbon dioxide and release water vapor that is then converted into precipitation that travels to all corners of the Earth.

Characteristics of the oceans

The oceans have the following characteristics:

They are made up of salt water.
They cover 71% of the planet's surface.
They contain more than 1.3 trillion cubic kilometers of water and have an average depth of 3,900 meters.
They represent 97% of the Earth's water supply.
They are the habitat of many species and a source of great biodiversity.
They are essential for the water cycle and climate regulation.
They are a source of resources for human beings.

Origin of the oceans

The oceans They were formed from the separation of the continents over geological time. 200 million years ago, all the current continents were united and formed a supercontinent called Pangea. At that time, the only ocean in existence was Panthalassa, which surrounded Pangea.

When the continents began to separate, the oceans we know today were formed. Thus, the separation of Africa, Europe and America formed the Atlantic Ocean; the separation of Africa and Oceania, the Indian Ocean; near the north pole, the Arctic Glacial Ocean was formed, and in the vicinity of Antarctica, the Antarctic Glacial Ocean was formed. The rest of Panthalassa made up the Pacific Ocean.

Composition of the oceans

The oceans are made up of salt water. Its composition is 97% H₂O and the rest are solid substances in solution, among which are sodium chloride (the most abundant and the one that explains the salinity), magnesium chloride, sodium sulfate, calcium chloride and potassium chloride.

The salinity of ocean water is due to various factorssuch as the salts carried by the rivers that flow into the sea, the high levels of evaporation that increase the concentration of salts and the volcanic eruptions that occur in the depths.

For these reasons, Not all oceans have the same salinity. In those ocean sectors where it is hotter and there is more evaporation, or where the rivers that flow into them transport a greater amount of sodium chloride, the water will be saltier.

Ocean temperature

Ocean temperatures vary depending on location, season, and depth.

Depending on location. Sectors of the oceans that are in warm regions have warmer water. Areas near the equator and the tropics have ocean temperatures that can exceed 30°C, while in polar regions ocean water can be below 0°C.
According to the season of the year. The temperature of ocean water increases in the summer months and decreases in the winter. In colder areas, during the winter months, water can drop below -1.9°C (this is the freezing point of salt water) and turn to ice.
Depending on the depth. As depth increases and the influence of the sun's heat decreases, the temperature of ocean water tends to drop. In the depths of the oceans, where sunlight does not reach, temperatures usually remain very close to the freezing point of -1.9 °C.

Flora and fauna of the oceans

The flora and fauna of the oceans are conditioned by the characteristics of the place where they develop.

Intertidal. It is the area where the sea connects with the main land. Due to the tide, twice a day the sea rises and submerges part of the coast, and twice a day it retreats and leaves a greater area of beach unsubmerged. The high levels of light and nutrients, together with the abundance of oxygen, make the intertidal zone a biologically productive environment, so that clams, snails and crabs can be found in abundance, and all types of plants, such as spartinas or algae .
Open sea. It is the region most densely populated by animals of all kinds. Ecosystem complexity decreases as depth increases. The variety of animal species is enormous: from small crabs to sharks and whales they make up highly developed ecosystems. Phytoplankton is the most abundant plant species in the ocean, and is essential for the production of oxygen on the planet through photosynthesis.
Ocean bottom. In shallow, less cold and brighter marine waters, organisms such as seagrass beds or coral reefs may appear. In the deepest ocean floors, between 6,000 and 9,000 meters deep, the lack of light, high pressure and low temperatures represent an important limitation for the development of life. The animals and plants found there have biological adaptations that allow them to survive in these conditions. An example of this is bioluminescent animals, which generate their own light, such as lanternfish.

ocean currents

Temperature differences in the oceans cause ocean currents, which are flows of water in motion within the oceans.. Equatorial and subtropical regions have warmer water than polar regions, and these temperature differences drive ocean circulation.

Ocean currents can be warm or cold:

The warm currentssuch as the Gulf and Kuroshio, transport warm water from equatorial regions to higher latitudes. This affects the climate of coastal areas and can lead to significant changes in local temperatures.
The cold currentssuch as California or Humboldt, transport cold water from high latitudes to equatorial regions and can significantly influence the temperatures and precipitation of the coastal areas they pass through.

Tides

The water in the oceans is never still, but is in constant movement due to the different types of tides that exist. Tides are periodic oscillations in sea level, which occur as a result of the gravitational forces exerted by the Moon and the Sun on the Earth.. This oceanic phenomenon is manifested in the regular rise and fall of the height of the sea.

The gravitational interaction of the Moon and the Sun generates two main types of tides: the tides of high tidewhich correspond to the floods of the sea, and the tides of low tidewhich are characterized by drops in sea level. These variations occur twice a day in most coastal areas.

Harbors and coastal areas often have tide tables that provide detailed information about the expected tides at a specific location, which is essential for boating, fishing and other ocean-related activities. Tides also play an important role in coastal ecology and geology, as they condition the distribution of marine species and influence coastal erosion.

Natural disasters in the oceans

A common natural disaster in the oceans is hurricanes, a meteorological phenomenon characterized by strong winds and heavy rain.. Hurricanes can cause devastating damage to coastal areas and the marine environment. These events are fueled by the evaporation of seawater and tend to increase in intensity as they move over warmer water. They are phenomena that occur only in those areas of the oceans that are found in warm climates.

Ocean pollution

Ocean pollution is a global phenomenon characterized by the introduction of harmful substances and waste into marine ecosystems. The main pollutants of the oceans can be classified into two broad categories:

chemical pollution. Toxic chemicals such as heavy metals (for example, mercury and lead) or pesticides and herbicides are the main chemical pollutants in the oceans. These can come from land-based sources, such as agricultural or industrial pollution, or from marine sources, such as ship spills and oil activities on continental shelves.
Plastic pollution. The accumulation of plastic waste in the oceans is a growing problem. Microplastics (tiny plastic fragments) and macroplastics (such as abandoned packaging and fishing nets) threaten marine life and affect water quality.

It is currently believed that there are five large “plastic islands” in the oceans, that is, huge accumulations of garbage floating in the water. The largest, located in the Pacific Ocean, has an approximate area of 1.6 million square kilometers and contains about 80,000 tons of plastics.

In response to these problems, the United Nations has established international conventions and agreements.. One of them is the MARPOL Convention (International Convention for the Prevention of Pollution from Ships), which regulates the discharge of hazardous substances and waste from ships into marine waters.

In addition, the United Nations Convention on the Law of the Sea (UNCLOS) establishes general principles to protect and preserve marine environments.

References

Aquae Foundation. (2021). Tsunamis: what they are and how they are generated. https://www.fundacionaquae.org/
United Nations. (2021). Plastic, which has already choked our oceans, will end up suffocating us all if we do not act quickly. UN News. https://news.un.org/
National Geographic. (2010). Oceans. https://www.nationalgeographic.es/
Núñez, S. (2022). What are tides and why do they occur?. EcologyGreen. https://www.ecologiaverde.com/
International Atomic Energy Agency. (sf). Pollution of the sea and coasts. https://www.iaea.org/