Ocean - AbsoluteAstronomy.com

Ocean

Encyclopedia

An ocean was a pseudo-geographical feature in classical antiquity, believed by the ancient Greeks and Romans to be the world-ocean, an enormous river encircling the world....

) is a major body of saline water

Seawater

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

, and a principal component of the hydrosphere

Hydrosphere

A hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....

. Approximately 71% of the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's surface

Surface

In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...

(~) is covered by ocean, a continuous body of water

World Ocean

The World Ocean, world ocean, or global ocean, is the interconnected system of the Earth's oceanic waters, and comprises the bulk of the hydrosphere, covering almost 71% of the Earth's surface, with a total volume of 1.332 billion cubic kilometres.The unity and continuity of the World Ocean, with...

that is customarily divided into several principal oceans and smaller sea

Sea

A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

s.

More than half of this area is over 3,000 metres (9,800 ft) deep. Average oceanic salinity

Salinity

Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

is around 35 parts per thousand (‰) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ‰. Scientists estimate that 230,000 marine species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

are currently known, but the total could be up to 10 times that number.

Overview

Though generally described as several 'separate' oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean

World Ocean

or global ocean. name="UNAoO">"Distribution of land and water on the planet". UN Atlas of the Oceans This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography

Oceanography

Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...

.

The major oceanic divisions are defined in part by the continent

Continent

A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...

s, various archipelago

Archipelago

An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...

s, and other criteria. These divisions are (in descending order of size):

Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, which separates Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

from the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, which separates the Americas from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

, which washes upon southern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

and separates Africa and Australia
Southern Ocean
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...

, sometimes considered an extension of the Pacific, Atlantic and Indian Oceans, which encircles Antarctica.
Arctic Ocean
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

, sometimes considered a sea
Sea
A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

of the Atlantic, which covers much of the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

and washes upon northern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

and Eurasia.

The Pacific and Atlantic may be further subdivided by the equator

Equator

An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

into northern and southern portions. Smaller regions of the oceans are called sea

Sea

s, gulfs

Headlands and bays

Headlands and bays are two related features of the coastal environment.- Geology and geography :Headlands and bays are often found on the same coastline. A bay is surrounded by land on three sides, whereas a headland is surrounded by water on three sides. Headlands are characterized by high,...

, bay

Bay

A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...

s, strait

Strait

A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...

s and other names.

Geologically, an ocean is an area of oceanic crust

Oceanic crust

Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

covered by water. Oceanic crust is the thin layer of solidified volcanic basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

that covers the Earth's mantle

Mantle (geology)

The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

. Continental crust

Continental crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...

is thicker but less dense. From this perspective, the earth has three oceans: the World Ocean, the Caspian Sea

Caspian Sea

The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...

, and Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

. The latter two were formed by the collision of Cimmeria

Cimmerian Plate

The Cimmerian Plate is an ancient tectonic plate that comprises parts of present-day Anatolia, Iran, Afghanistan, Tibet, Indochina and Malaya regions. The Cimmerian Plate was formerly part of the ancient supercontinent of Pangaea. Pangaea was shaped like a vast "C", facing east, and inside of the...

with Laurasia

Laurasia

In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...

. The Mediterranean Sea

Mediterranean Sea

The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

is at times a discrete ocean, because tectonic plate movement

Plate tectonics

Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

has repeatedly broken its connection to the World Ocean through the Strait of Gibraltar

Strait of Gibraltar

The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain in Europe from Morocco in Africa. The name comes from Gibraltar, which in turn originates from the Arabic Jebel Tariq , albeit the Arab name for the Strait is Bab el-Zakat or...

. The Black Sea is connected to the Mediterranean through the Bosporus

Bosporus

The Bosphorus or Bosporus , also known as the Istanbul Strait , is a strait that forms part of the boundary between Europe and Asia. It is one of the Turkish Straits, along with the Dardanelles...

, but the Bosporus is a natural canal

Canal

Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

cut through continental rock some 7,000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.

Despite their names, smaller landlocked

Landlocked

A landlocked country is a country entirely enclosed by land, or whose only coastlines lie on closed seas. There are 48 landlocked countries in the world, including partially recognized states...

bodies of saltwater that are not connected with the World Ocean, such as the Aral Sea

Aral Sea

The Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...

, are actually salt lake

Salt lake

A salt lake or saline lake is a landlocked body of water which has a concentration of salts and other dissolved minerals significantly higher than most lakes . In some cases, salt lakes have a higher concentration of salt than sea water, but such lakes would also be termed hypersaline lakes...

Borders of the oceans

For a detailed list of the borders of the oceans, see Borders of the oceans

Borders of the oceans

The borders of the oceans are the limits of the several oceans of the Earth. The definition, as well as the number of oceans can vary depending on the adopted criteria.-Overview:...

Ocean and life

The ocean has a significant effect on the biosphere

Biosphere

The biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth, a closed and self-regulating system...

. Oceanic evaporation

Evaporation

Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

, as a phase of the water cycle

Water cycle

The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapor, and solid at various places in the water cycle...

, is the source of most rain

Rain

Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

fall, and ocean temperatures determine climate

Climate

Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

and wind

Wind

Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

patterns that affect life on land.
Life

Life

Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

within the ocean evolved

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

3 billion years prior to life on land. Both the depth and distance from shore strongly influence the amount and kinds of plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s and animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s that live there.

Physical properties

The area of the World Ocean is 361 million square kilometres (139 million square miles)
Its volume is approximately 1.3 billion cubic kilometres (310 million cu mi). This can be thought of as a cube of water with an edge length of 1111 kilometres (690.3 mi). Its average depth is 3790 metres (12,434.4 ft), and its maximum depth is 10923 metres (6.8 mi) Nearly half of the world's marine waters are over 3000 metres (9,842.5 ft) deep. The vast expanses of deep ocean (anything below 200 metres (656.2 ft)) cover about 66% of the Earth's surface. This does not include seas not connected to the World Ocean, such as the Caspian Sea

Caspian Sea

The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...

.

The total mass of the hydrosphere

Hydrosphere

A hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....

is about 1.4E+18 metric ton or 1.4×10²¹ kg, which is about 0.023 percent of the Earth's total mass. Less than 3 percent is freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

; the rest is saltwater

Seawater

, mostly in the ocean.

Color

A common misconception is that the oceans are blue primarily because the sky is blue. In fact, water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

has a very slight blue color that can only be seen in large volumes. While the sky's reflection does contribute to the blue appearance of the surface, it is not the primary cause. The primary cause is the absorption by the water

Water

molecules of red photons from the incoming light, the only known example of color in nature resulting from vibrational, rather than electronic, dynamics.

Glow

Sailors and other mariners have reported that the ocean often emits a visible glow, or luminescence, which extends for miles at night. In 2005, scientists announced that for the first time, they had obtained photographic evidence of this glow. It may be caused by bioluminescence

Bioluminescence

Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

Exploration

Ocean travel by boat dates back to prehistoric times, but only in modern times has extensive underwater travel become possible.

The deepest point in the ocean is the Mariana Trench

Mariana Trench

The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

, located in the Pacific Ocean near the Northern Mariana Islands

Northern Mariana Islands

The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands , is a commonwealth in political union with the United States, occupying a strategic region of the western Pacific Ocean. It consists of 15 islands about three-quarters of the way from Hawaii to the Philippines...

. Its maximum depth has been estimated to be 10971 metres (35,994.1 ft) (plus or minus 11 meters; see the Mariana Trench

Mariana Trench

article for discussion of the various estimates of the maximum depth.) The British naval vessel, Challenger II surveyed the trench in 1951 and named the deepest part of the trench, the "Challenger Deep

Challenger Deep

The Challenger Deep is the deepest known point in the oceans, with a depth of to by direct measurement from submersibles, and slightly more by sonar bathymetry . It is located at the southern end of the Mariana Trench near the Mariana Islands group...

". In 1960, the Trieste

Bathyscaphe Trieste

The Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe with a crew of two, which reached a record maximum depth of about , in the deepest known part of the Earth's oceans, the Challenger Deep, in the Mariana Trench near Guam, on January 23, 1960, crewed by Jacques Piccard ...

successfully reached the bottom of the trench, manned by a crew of two men.

Much of the ocean bottom remains unexplored and unmapped. A global image of many underwater features larger than 10 kilometres (6.2 mi) was created in 1995 based on gravitational distortions of the nearby sea surface.

Regions and depths

Oceanographers divide the ocean into regions depending on physical and biological conditions of these areas. The pelagic zone

Pelagic zone

Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...

includes all open ocean regions, and can be divided into further regions categorized by depth and light abundance. The photic zone

Photic zone

The photic zone or euphotic zone is the depth of the water in a lake or ocean that is exposed to sufficient sunlight for photosynthesis to occur...

covers the oceans from surface level to 200 metres down. This is the region where photosynthesis can occur and therefore is the most biodiverse. Since plants require photosynthesis, life found deeper than this must either rely on material sinking from above (see marine snow

Marine snow

In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he...

) or find another energy source; hydrothermal vents are the primary option in what is known as the aphotic zone

Aphotic zone

The aphotic zone is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1% of sunlight penetrates. Consequently, bioluminescence is essentially the only light found in this zone...

(depths exceeding 200 m). The pelagic part of the photic zone is known as the epipelagic. The pelagic part of the aphotic zone can be further divided into regions that succeed each other vertically according to temperature.
The mesopelagic

Mesopelagic

The mesopelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all...

is the uppermost region. Its lowermost boundary is at a thermocline

Thermocline

A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

of 12 °C (53.6 °F), which, in the tropics generally lies at 700–1000 m (2,296.6–3,280.8 ft). Next is the bathypelagic lying between 10 and 4 °C (50 and 39.2 F), typically between 700–1000 m (2,296.6–3,280.8 ft) and 2000–4000 m (6,561.7–13,123.4 ft) Lying along the top of the abyssal plain

Abyssal plain

An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3000 and 6000 metres. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest...

is the abyssalpelagic

Abyssal zone

The abyssal zone is the abyssopelagic layer or pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres , this zone remains in perpetual darkness and never receives...

, whose lower boundary lies at about 6000 metres (19,685 ft). The last zone includes the deep trenches, and is known as the hadalpelagic

Hadal zone

The hadal zone , also known as the hadopelagic zone and trench zone, is the delineation for the deepest trenches in the ocean...

. This lies between 6000–11000 m (19,685–36,089.2 ft) and is the deepest oceanic zone.

Along with pelagic aphotic zones there are also benthic aphotic zones. These correspond to the three deepest zones of the deep-sea. The bathyal zone

Bathyal zone

The bathyal zone or bathypelagic – from Greek βαθύς , deep – is that part of the pelagic zone that extends from a depth of 1000 to 4000 metres below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The average temperature hovers at about 39°F...

covers the continental slope down to about 4000 metres (13,123.4 ft). The abyssal zone covers the abyssal plains between 4,000 and 6,000 m. Lastly, the hadal zone corresponds to the hadalpelagic zone which is found in the oceanic trenches.
The pelagic zone can also be split into two subregions, the neritic zone

Neritic zone

The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...

and the oceanic zone

Oceanic zone

The oceanic zone begins in the area off shore where the water measures 200 meters deep or deeper.It is the region of open sea beyond the edge of the continental shelf and includes 65% of the ocean’s completely open water...

. The neritic encompasses the water mass directly above the continental shelves, while the oceanic zone includes all the completely open water.
In contrast, the littoral zone covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the intertidal zone because it is the area where tide level affects the conditions of the region.

Geology

The ocean floor spreads from mid-ocean ridge

Mid-ocean ridge

A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges , typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading...

s where two plates

Plate tectonics

Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

adjoin. Where two plates move towards each other, one plate subducts

Subduction

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

under another plate (oceanic or continental) leading to an oceanic trench

Oceanic trench

The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor....

Climate effects

Ocean current

An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...

s greatly affect the Earth's climate

Climate

by transferring heat from the tropics to the polar regions, and transferring warm or cold air and precipitation to coastal regions, where winds may carry them inland. Surface heat and freshwater flux

Flux

In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...

es create global density gradient

Density Gradient

Density gradient is a spatial variation in density over an area. The term is used in the natural sciences to describe varying density of matter, but can apply to any quantity whose density can be measured...

s that drive the thermohaline circulation

Thermohaline circulation

The term thermohaline circulation refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....

part of large-scale ocean circulation. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation. Changes in the thermohaline circulation are thought to have significant impacts on the Earth's radiation budget. Insofar as the thermohaline circulation governs the rate at which deep waters reach the surface, it may also significantly influence atmospheric carbon dioxide concentrations.

For a discussion of the possibilities of changes to the thermohaline circulation under global warming

Global warming

Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

, see shutdown of thermohaline circulation

Shutdown of thermohaline circulation

Shutdown or slowdown of the thermohaline circulation is a postulated effect of global warming.There is some speculation that global warming could, via a shutdown or slowdown of the thermohaline circulation, trigger localised cooling in the North Atlantic and lead to cooling, or lesser warming, in...

.

It is often stated that the thermohaline circulation is the primary reason that the climate of Western Europe is so temperate. An alternate hypothesis claims that this is largely incorrect, and that Europe is warm mostly because it lies downwind of an ocean basin, and because atmospheric waves bring warm air north from the subtropics

Subtropics

The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...

.

The Antarctic Circumpolar Current

Antarctic Circumpolar Current

The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...

encircles that continent, influencing the area's climate and connecting currents in several oceans.

One of the most dramatic forms of weather

Weather

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

occurs over the oceans: tropical cyclone

Tropical cyclone

A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

s (also called "typhoons" and "hurricanes" depending upon where the system forms).

Biology

Lifeforms native to oceans include:

Radiata
Radiata
The Radiata are the radially symmetric animals of the Eumetazoa subkingdom. The term Radiata has had various meanings in the history of classification...
Fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
Cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...

such as whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s, dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s and porpoise
Porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...

s,
Cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s such as octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...

and squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
Crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s such as lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...

s, clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...

s, shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

and krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
Marine worm
Marine worm
Any worm that lives in a marine environment is considered a marine worm. Marine worms are found in several different phyla, including the Platyhelminthes, Nematoda, Annelida , Chaetognatha, Hemichordata, and Phoronida....

s
Plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
Echinoderms such as brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...

s, starfish, sea cucumber
Sea cucumber
Sea cucumbers are echinoderms from the class Holothuroidea.They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian species and genera, many of which are targeted...

s and sand dollar
Sand dollar
The term Sand dollar refers to species of extremely flattened, burrowing echinoids belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits...

s.

Economy

The oceans are essential to transportation: most of the world's goods move by ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

between the world's seaports.

Oceans are also the major supply source for the fishing industry

Fishing industry

The fishing industry includes any industry or activity concerned with taking, culturing, processing, preserving, storing, transporting, marketing or selling fish or fish products....

. Some of the more major ones are shrimp

Shrimp

Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

, fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, crabs and lobster

Lobster

Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...

Ancient oceans

Continental drift

Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...

continually reconfigures the oceans, joining and splitting bodies of water. Ancient oceans include:

Bridge River Ocean
Bridge River Ocean
The Bridge River Ocean was an ancient ocean that existed between North America and the Insular Islands during the Paleozoic time. Like the earlier Slide Mountain Ocean the Bridge River Ocean had a subduction zone on the ocean floor called the Insular Trench...

, the ocean between the ancient Insular Islands
Insular Islands
The Insular Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Cretaceous time that rode on top a microplate called the Insular Plate, beginning around 130 million years ago. The Insular Islands were surrounded by two prehistoric oceans; the Panthalassa...

and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

.
Iapetus Ocean
Iapetus Ocean
The Iapetus Ocean was an ocean that existed in the Neoproterozoic and Paleozoic eras of the geologic timescale . The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia...

, the southern hemisphere ocean between Baltica
Baltica
Baltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...

and Avalonia
Avalonia
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States...

.
Panthalassa
Panthalassa
Panthalassa , also known as the Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea, during the late Paleozoic and the early Mesozoic years. It included the Pacific Ocean to the west and north and the Tethys Ocean to the southeast...

, the vast world ocean that surrounded the Pangaea
Pangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....

supercontinent.
Rheic Ocean
Rheic Ocean
The Rheic Ocean was a Paleozoic ocean between the large continent Gondwana to the south and the microcontinents Avalonia and others to the north...
Slide Mountain Ocean
Slide Mountain Ocean
The Slide Mountain Ocean was an ancient ocean that existed between the Intermontane Islands and North America in the Triassic time beginning around 245 million years ago. Its name origin comes from the Slide Mountain Terrane, a region made of rocks from the floor of the ancient ocean...

, the ocean between the ancient Intermontane Islands
Intermontane Islands
The Intermontane Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Triassic time beginning around 245 million years ago. They were 600 to long and rode atop a microplate known as the Intermontane Plate...

and North America.
Tethys Ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...

, the ocean between the ancient continents of Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

and Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...

.
Khanty Ocean
Khanty Ocean
Khanty Ocean was an ancient, small ocean that existed near the end of the Precambrian time to the Silurian. It was between Baltica and the Siberian continent, with the bordering oceans of Panthalassa to the north, Proto-Tethys to the northeast, and Paleo-Tethys to the south and east...

, the ocean between Baltica and Siberia.
Mirovia
Mirovia
Mirovia was a hypothesized superocean which may have been a global ocean surrounding the supercontinent Rodinia in the Neoproterozoic Era, about 1 billion to 750 million years ago. The Mirovia may be essentially identical to, or the precursor of, the hypothesized Pan-African Ocean, which followed...

, the ocean that surrounded the Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...

supercontinent.
Paleo-Tethys Ocean
Paleo-Tethys Ocean
The Paleo-Tethys Ocean was an ancient Paleozoic ocean. It was located between the paleocontinent Gondwana and the so called Hunic terranes. These are divided into the European Hunic and Asiatic Hunic...

, the ocean between Gondwana and the Hunic terranes.
Poseidon Ocean
Poseidon Ocean
The Poseidon Ocean is a supposed ocean that existed in the Mesoproterozoic period of the geologic timescale . It began to form when a hotspot collided with lithosphere that was already in an extensional regime that allowed rifting to occur at the onset of hotspot volcanism that created the...
Proto-Tethys Ocean
Proto-Tethys Ocean
The Proto-Tethys Ocean was an ancient ocean that existed from the latest Ediacaran to the Carboniferous . It was an ocean predecessor of the later Paleo-Tethys Ocean. The ocean formed when Pannotia disintegrated, Proto-Laurasia rifted away from a supercontinent that would become Gondwana...
Pan-African Ocean
Pan-African Ocean
The Pan-African Ocean is a hypothesized paleo-ocean whose closure created the supercontinent of Pannotia. The ocean may have existed before the break-up of the supercontinent of Rodinia. The ocean closed before the beginning of the Phanerozoic Eon, when the Panthalassa ocean expanded, and was...

, the ocean that surrounded the Pannotia
Pannotia
Pannotia, first described by Ian W. D. Dalziel in 1997, is a hypothetical supercontinent that existed from the Pan-African orogeny about six hundred million years ago to the end of the Precambrian about five hundred and fifty million years ago. It is also known as the Vendian supercontinent...

supercontinent.
Superocean
Superocean
A superocean is an ocean which surrounds a supercontinent. It is less commonly defined as any ocean larger than the current Pacific Ocean. Named global superoceans include Mirovia, which surrounded the supercontinent Rodinia, and Panthalassa, which surrounded the supercontinent Pangaea...

, the ocean that surrounds a global supercontinent.
Ural Ocean
Ural Ocean
The Ural Ocean was a small, ancient ocean that was situated between Siberia and Baltica. The ocean formed in the Late Ordovician epoch, when large islands from Siberia collided with Baltica, which was now part of a minor supercontinent of Euramerica. The islands also caused Ural Ocean's precursor,...

, the ocean between Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

and Baltica
Baltica
Baltica is a name applied by geologists to a late-Proterozoic, early-Palaeozoic continent that now includes the East European craton of northwestern Eurasia. Baltica was created as an entity not earlier than 1.8 billion years ago. Before this time, the three segments/continents that now comprise...

.

Extraterrestrial oceans

Culture

The original concept of "ocean" goes back to notions of Mesopotamian and Indo-European mythology, imagining the world to be encircled by a great river. Okeanos

Oceanus

Oceanus ; , Ōkeanós) was a pseudo-geographical feature in classical antiquity, believed by the ancient Greeks and Romans to be the world-ocean, an enormous river encircling the world....

in Greek

Greek mythology

Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

, reflects the ancient Greek observation that a strong current flowed off Gibraltar

Gibraltar

Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...

and their subsequent assumption that it was a great river. (Compare also Samudra

Samudra

Samudra is a Sanskrit term for "ocean", literally the "gathering together of waters" Samudra is a Sanskrit term for "ocean", literally the "gathering together of waters" Samudra is a Sanskrit term for "ocean", literally the "gathering together of waters" (- meaning "together" and -udra meaning...

from Hindu mythology

Hindu mythology

Hindu religious literature is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Nepali and Indian culture...

and Jörmungandr

Jörmungandr

In Norse mythology, Jörmungandr , mostly known as Jormungand, orJörmungand , or Midgard Serpent , or World Serpent, is a sea serpent, and the middle child of the giantess Angrboða and the god Loki...

from Norse mythology

Norse mythology

Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

.) The world was imagined to be enclosed by a celestial ocean

Celestial ocean

Several mythologies have the notion of a celestial ocean or river, enveloping the world both above the heavenly sphere and below the underworld.See also:*Oceanus*Uranos*Styx*Rasā*Samudra*Varuna*Sea...

above the heavens, and an ocean of the underworld below.

Artworks which depict maritime themes are known as marine art

Marine art

Marine art or maritime art is any form of figurative art that portrays or draws its main inspiration from the sea. Maritime painting is a genre that depicts ships and the sea—a genre particularly strong from the 17th to 19th centuries...

, a term which particularly applies to common styles of European painting of the 17th to 19th centuries.

External links

National Oceanic and Atmospheric Administration
Marine forecasts for any ocean point – Buoyweather is a helpful link for marine safety
Council on Foreign Relations, Interactive Guide to Oceans Governance
Smithsonian Ocean Portal

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Overview

Borders of the oceans

Ocean and life

Physical properties

Color

Glow

Exploration

Regions and depths

Geology

Climate effects

Biology

Economy

Ancient oceans

Extraterrestrial oceans

Culture

Further reading

External links