World map of the five-ocean model with approximate boundaries
World map of the five-ocean model with approximate boundaries

The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water.[1] An ocean can also refer to any of the large bodies of water into which the world ocean is conventionally divided.[2] Separate names are used to identify five different areas of the ocean: Pacific (the largest), Atlantic, Indian, Southern (Antarctic), and Arctic (the smallest).[3][4] Seawater covers approximately 361,000,000 km2 (139,000,000 sq mi) of the planet. The ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth. Acting as a huge heat reservoir, the ocean influences climate and weather patterns, the carbon cycle, and the water cycle.

Oceanographers divide the ocean into different vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column from surface to ocean floor throughout the open ocean. The water column is further categorized in other zones depending on depth and on how much light is present. The photic zone includes water from the surface to a depth of 1% of the surface light (about 200 m in the open ocean), where photosynthesis can occur. This makes the photic zone the most biodiverse. Photosynthesis by plants and microscopic algae (free floating phytoplankton) creates organic matter using light, water, carbon dioxide, and nutrients. Ocean photosynthesis creates 50% of the oxygen in earth's atmosphere.[5] This upper sunlit zone is the origin of the food supply which sustains most of the ocean ecosystem. Light only penetrates to a depth of a few hundred meters; the remaining ocean below is cold and dark. The continental shelf where the ocean approaches dry land is more shallow, with a depth of a few hundred meters or less. Human activity has a greater impact on the continental shelf.  

Ocean temperatures depend on the amount of solar radiation reaching the ocean surface. In the tropics, surface temperatures can rise to over 30 °C (86 °F). Near the poles where sea ice forms, the temperature in equilibrium is about −2 °C (28 °F). Deep ocean temperature is between −2 °C (28 °F) and 5 °C (41 °F) in all parts of the ocean.[6] Water continuously circulates in the oceans creating ocean currents. These directed movements of seawater are generated by forces acting upon the water, including temperature differences, atmospheric circulation (wind), the Coriolis effect and differences in salinity.[7] Tidal currents originate from tides, while surface currents are caused by wind and waves. Major ocean currents include the Gulf Stream, Kuroshio Current, Agulhas Current and Antarctic Circumpolar Current. Collectively, currents move enormous amounts of water and heat around the globe. This circulation significantly impacts global climate and the uptake and redistribution of pollutants such as carbon dioxide by moving these contaminants from the surface into the deep ocean.

Ocean water contains large quantities of dissolved gases, including oxygen, carbon dioxide and nitrogen. This gas exchange takes place at the ocean surface and solubility depends on the temperature and salinity of the water.[8] The increasing concentration of carbon dioxide in the atmosphere due to fossil fuel combustion leads to higher concentrations in ocean water, resulting in ocean acidification.[9] The ocean provides society with important environmental services, including climate regulation. It also offers a means of trade and transport and access to food and other resources. Known to be the habitat of over 230,000 species, it may contain far more – perhaps over two million species.[10] However, the ocean is subject to numerous human-caused environmental threats, including marine pollution, overfishing, and effects of climate change on oceans, such as ocean warming, ocean acidification, sea level rise and many more. The continental shelf and coastal waters that are most influenced by human activity are especially vulnerable.


Ocean and sea

The terms "the ocean" or "the sea" used without specification refer to the interconnected body of salt water covering the majority of the Earth's surface.[3][4] It includes the Atlantic, Pacific, Indian, Southern and Arctic Oceans.[11] As a general term, "the ocean" and "the sea" are often interchangeable, although speakers of British English refer to "the sea" in all cases,[12] even when the body of water is one of the oceans.

Strictly speaking, a "sea" is a body of water (generally a division of the world ocean) partly or fully enclosed by land.[13] The word "sea" can also be used for many specific, much smaller bodies of seawater, such as the North Sea or the Red Sea. There is no sharp distinction between seas and oceans, though generally seas are smaller, and are often partly (as marginal seas) or wholly (as inland seas) bordered by land.[14]

World ocean

Further information: Ocean current, Thermohaline circulation, and Ocean general circulation model

The contemporary concept of the World Ocean was coined in the early 20th century by the Russian oceanographer Yuly Shokalsky to refer to the continuous ocean that covers and encircles most of Earth.[15][16] The global, interconnected body of salt water is sometimes referred to as the world ocean, global ocean or the great ocean.[17][18][19] The concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[20]


The word ocean comes from the figure in classical antiquity, Oceanus (/ˈsənəs/; Greek: Ὠκεανός Ōkeanós,[21] pronounced [ɔːkeanós]), the elder of the Titans in classical Greek mythology. Oceanus was believed by the ancient Greeks and Romans to be the divine personification of an enormous river encircling the world.

The concept of Ōkeanós has an Indo-European connection. Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases.[22]

Natural history

Further information: List of ancient oceans and Origin of water on Earth

During planetary formation Earth possibly had magma oceans. Subsequently outgassing, volcanic activity and meteorite impacts, according to current theories, produced an early atmosphere of carbon dioxide, nitrogen and water vapor. The gases and with them the atmosphere are thought to have accumulated over millions of years and after Earth's surface had significantly cooled the water vapor over time would have condensed, forming Earth's first oceans.[23] The early oceans might have been significantly hotter than today and appeared green due to high iron content.[24]

Geological evidence helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption) was recovered from the Isua Greenstone Belt and provides evidence that water existed on Earth 3.8 billion years ago.[25] In the Nuvvuagittuq Greenstone Belt, Quebec, Canada, rocks dated at 3.8 billion years old by one study[26] and 4.28 billion years old by another[27] show evidence of the presence of water at these ages.[25] If oceans existed earlier than this, any geological evidence either has yet to be discovered or has since been destroyed by geological processes like crustal recycling. However, more recently, in August 2020, researchers reported that sufficient water to fill the oceans may have always been on the Earth since the beginning of the planet's formation.[28][29][30] In this model, atmospheric greenhouse gases kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity.[31] By 3.5 Ga, Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.[32]

Since its formation the ocean has taken many conditions and shapes with many past ocean divisions and potentially at times covering the whole globe.[33]

During colder climatic periods, more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age, glaciers covered almost one-third of Earth's land mass with the result being that the oceans were about 122 m (400 ft) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 5.5 m (18 ft) higher than they are now. About three million years ago the oceans could have been up to 50 m (165 ft) higher.[34]


Further information: Water distribution on Earth

The ocean covers ~70% of the Earth, sometimes called the "blue planet"
The ocean covers ~70% of the Earth, sometimes called the "blue planet"
The Atlantic, one component of the system, makes up 23% of the "global ocean".
The Atlantic, one component of the system, makes up 23% of the "global ocean".

The entire ocean, containing 97% of Earth's water, spans 70.8% of Earth's surface,[1] making it Earth's global ocean or world ocean.[15][17] This makes Earth, along with its vibrant hydrosphere a "water world"[35][36] or "ocean world",[37][38] particularly in Earth's early history when the ocean is thought to have possibly covered Earth completely.[33] The ocean is shaped irregularly, dominating Earth's surface unevenly, allowing the decernment of Earth's surface into a water and land hemisphere, as well as the division of the ocean into particular oceans.

Oceanic divisions

Further information: Borders of the oceans

The major oceanic divisions – listed below in descending order of area and volume – are so named based on nearest continents, various archipelagos, and other criteria.[39][40][41] Oceans are fringed with coastlines that run for 360,000 kilometres in total distance.[42][43] They are also connected to smaller, adjoining bodies of water such as, seas, gulfs, bays, bights, and straits. Seawater covers approximately 361,000,000 km2 (139,000,000 sq mi) and is customarily divided into five principal oceans, as below:

Oceans by size
# Ocean Location Area
Avg. depth
1 Pacific Ocean Between Asia and Australasia and the Americas[45] 168,723,000
3,970 135,663
2 Atlantic Ocean Between the Americas and Europe and Africa[46] 85,133,000
3,646 111,866
3 Indian Ocean Between southern Asia, Africa and Australia[47] 70,560,000
3,741 66,526
4 Southern Ocean Between Antarctica and the Pacific, Atlantic and Indian oceans
Sometimes considered an extension of those three oceans.[48][49]
3,270 17,968
5 Arctic Ocean Between northern North America and Eurasia in the Arctic
Sometimes considered a marginal sea of the Atlantic.[50][51][52]
1,205 45,389
Total 361,900,000
3,688 377,412
NB: Volume, area, and average depth figures include NOAA ETOPO1 figures for marginal South China Sea.
Sources: Encyclopedia of Earth,[45][46][47][48][52] International Hydrographic Organization,[49] Regional Oceanography: an Introduction (Tomczak, 2005),[50] Encyclopædia Britannica,[51] and the International Telecommunication Union.[44]

Ocean ridges and ocean basins

World distribution of mid-oceanic ridges; USGS
World distribution of mid-oceanic ridges; USGS

Every ocean basin has a mid-ocean ridge, which creates a long mountain range beneath the ocean. Together they form the global mid-oceanic ridge system that features the longest mountain range in the world. The longest continuous mountain range is 65,000 km (40,000 mi). This underwater mountain range is several times longer than the longest continental mountain range—the Andes.[53]

Oceanographers state that less than 20% of the oceans have been mapped.[54]


Main article: Origin of water on Earth

The origin of Earth's oceans is unknown. Oceans are thought to have formed in the Hadean eon and may have been the cause for the emergence of life. Scientists believe that a sizable quantity of water would have been in the material that formed the Earth.[55] Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. This is called atmospheric escape.

Plate tectonics, post-glacial rebound, and sea level rise continually change the coastline and structure of the world ocean. A global ocean has existed in one form or another on Earth for eons.

Physical properties


The volume of water in all the oceans together is approximately 1.335 billion cubic kilometers (1.335 sextillion liters, 320.3 million cubic miles).[39][56][57]

It has been estimated that there are 1.386 billion cubic kilometres (333 million cubic miles) of water on Earth.[58][59][60] This includes water in gaseous, liquid and frozen forms as soil moisture, groundwater and permafrost in the Earth's crust (to a depth of 2 km); oceans and seas, lakes, rivers and streams, wetlands, glaciers, ice and snow cover on Earth's surface; vapour, droplets and crystals in the air; and part of living plants, animals and unicellular organisms of the biosphere. Saltwater accounts for 97.5% of this amount, whereas fresh water accounts for only 2.5%. Of this fresh water, 68.9% is in the form of ice and permanent snow cover in the Arctic, the Antarctic and mountain glaciers; 30.8% is in the form of fresh groundwater; and only 0.3% of the fresh water on Earth is in easily accessible lakes, reservoirs and river systems.[61]

The total mass of Earth's hydrosphere is about 1.4 × 1018 tonnes, which is about 0.023% of Earth's total mass. At any given time, about 2 × 1013 tonnes of this is in the form of water vapor in the Earth's atmosphere (for practical purposes, 1 cubic metre of water weighs 1 tonne). Approximately 71% of Earth's surface, an area of some 361 million square kilometres (139.5 million square miles), is covered by ocean. The average salinity of Earth's oceans is about 35 grams of salt per kilogram of sea water (3.5%).[62]


Map of large underwater features (1995, NOAA)
Map of large underwater features (1995, NOAA)

The average depth of the oceans is about 4 km. More precisely the average depth is 3,688 meters (12,100 ft).[39] Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep.[19] "Deep ocean," which is anything below 200 meters (660 ft.), covers about 66% of Earth's surface.[63] This figure does not include seas not connected to the World Ocean, such as the Caspian Sea.

The deepest point in the ocean is the Mariana Trench, located in the Pacific Ocean near the Northern Mariana Islands.[64] Its maximum depth has been estimated to be 10,971 meters (35,994 ft). The British naval vessel Challenger II surveyed the trench in 1951 and named the deepest part of the trench the "Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench, manned by a crew of two men.


Ocean chlorophyll concentration is a proxy for phytoplankton biomass. In this map, blue colors represent lower chlorophyll and reds represent higher chlorophyll. Satellite-measured chlorophyll is estimated based on ocean color by how green the color of the water appears from space.
Ocean chlorophyll concentration is a proxy for phytoplankton biomass. In this map, blue colors represent lower chlorophyll and reds represent higher chlorophyll. Satellite-measured chlorophyll is estimated based on ocean color by how green the color of the water appears from space.

Most of the ocean is blue in color, but in some places the ocean is blue-green, green, or even yellow to brown.[65] Blue ocean color is a result of several factors. First, water preferentially absorbs red light, which means that blue light remains and is reflected back out of the water. Red light is most easily absorbed and thus does not reach great depths, usually to less than 50 meters (164 ft.). Blue light, in comparison, can penetrate up to 200 meters (656 ft.).[66] Second, water molecules and very tiny particles in ocean water preferentially scatter blue light more than light of other colors. Blue light scattering by water and tiny particles happens even in the very clearest ocean water,[67] and is similar to blue light scattering in the sky.

The main substances that affect the color of the ocean include dissolved organic matter, living phytoplankton with chlorophyll pigments, and non-living particles like marine snow and mineral sediments.[68] Chlorophyll can be measured by satellite observations and serves as a proxy for ocean productivity (marine primary productivity) in surface waters. In long term composite satellite images, regions with high ocean productivity show up in yellow and green colors because they contain more (green) phytoplankton, whereas areas of low productivity show up in blue.

Oceanic zones

Further information: Stratification (water)

The major oceanic zones, based on depth and biophysical conditions
The major oceanic zones, based on depth and biophysical conditions

Oceanographers divide the ocean into different vertical and horizontal zones defined by physical and biological conditions. The pelagic zone consists of the water column of the open ocean, and can be divided into further regions categorized by light abundance and by depth.

Grouped by light penetration

Grouped by depth and temperature

The pelagic part of the aphotic zone can be further divided into vertical regions according to depth and temperature:[69]

Distinct boundaries between ocean surface waters and deep waters can be drawn based on the properties of the water. These boundaries are called thermoclines (temperature), haloclines (salinity), chemoclines (chemistry), and pycnoclines (density). If a zone undergoes dramatic changes in temperature with depth, it contains a thermocline, a distinct boundary between warmer surface water and colder deep water. The tropical thermocline is typically deeper than the thermocline at higher latitudes. Polar waters, which receive relatively little solar energy, are not stratified by temperature and generally lack a thermocline because surface water at polar latitudes are nearly as cold as water at greater depths. Below the thermocline, water everywhere in the ocean is very cold, ranging from −1°C to 3°C. Because this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9°C.[70] If a zone undergoes dramatic changes in salinity with depth, it contains a halocline. If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a chemocline. Temperature and salinity control the density of ocean water, with colder and saltier water being more dense, and this density in turn regulates the global water circulation within the ocean.[69] The halocline often coincides with the thermocline, and the combination produces a pronounced pycnocline, a boundary between less dense surface water and dense deep water.

Grouped by distance from land

The pelagic zone can be further subdivided into two sub regions based on distance from land: the neritic zone and the oceanic zone. The neritic zone encompasses the water mass directly above the continental shelves and hence includes coastal waters, whereas the oceanic zone includes all the completely open water.

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.[69]


Main articles: Ocean temperature and Ocean heat content

Ocean temperatures depends on the amount of solar radiation falling on its surface. In the tropics, with the Sun nearly overhead, the temperature of the surface layers can rise to over 30 °C (86 °F) while near the poles the temperature in equilibrium with the sea ice is about −2 °C (28 °F). There is a continuous circulation of water in the oceans. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface. Deep ocean water has a temperature between −2 °C (28 °F) and 5 °C (41 °F) in all parts of the globe.[6]

It is clear that the oceans are warming as a result of climate change and this rate of warming is increasing.[71]: 9  The upper ocean (above 700 m) is warming fastest, but the warming trend extends throughout the ocean. Most of the ocean heat gain is taking place in the Southern Ocean. For example, the temperature of the Antarctic Southern Ocean rose by 0.17 °C (0.31 °F) between the 1950s and the 1980s, nearly twice the rate for the world's oceans as a whole.[72] From 1960 to through 2019, the average temperature for the upper 2000 meters of the oceans has increased by 0.12 degree Celsius, whereas the ocean surface temperature has warmed up to 1.2 degree Celsius from the pre-industrial era.[73] The warming rate varies with depth: at a depth of a thousand metres the warming occurs at a rate of almost 0.4 °C per century (data from 1981 to 2019), whereas the warming rate at two kilometres depth is only half.[74]: 463 

Sea ice

Main articles: Sea ice and Arctic sea ice decline

Seawater with a typical salinity of 35‰ has a freezing point of about −1.8°C (28.8°F).[69][75] Because sea ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans.[76][77][78] Sea ice usually starts to freeze at the very surface, initially as a very thin ice film. As further freezing takes place, this ice film thickens and can form ice sheets. The ice formed incorporates some sea salt, but much less than the seawater it forms from. As the ice forms with low salinity this results in saltier residual seawater. This in turn increases density and promotes vertical sinking of the water.[79]

Ocean currents and global climate

Ocean surface currents
Ocean surface currents
A map of the global thermohaline circulation; blue represents deep-water currents, whereas red represents surface currents.
A map of the global thermohaline circulation; blue represents deep-water currents, whereas red represents surface currents.

See also: Effects of climate change on oceans § Changing ocean currents

Types of ocean currents

An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, temperature and salinity differences.[7] Ocean currents are primarily horizontal water movements. They have different origins, such as tides for tidal currents, or wind and waves for surface currents.

Tidal currents are in phase with the tide, hence are quasiperiodic; associated with the influence of the moon and sun pull on the ocean water. Tidal currents may form various complex patterns in certain places, most notably around headlands.[80] Non-periodic or non-tidal currents are created by the action of winds and changes in density of water. In littoral zones, breaking waves are so intense and the depth measurement so low, that maritime currents reach often 1 to 2 knots.[81]

The wind and waves create surface currents (designated as "drift currents"). These currents can decompose in one quasi-permanent current (which varies within the hourly scale) and one movement of Stokes drift under the effect of rapid waves movement (which vary on timescales of a couple of seconds). The quasi-permanent current is accelerated by the breaking of waves, and in a lesser governing effect, by the friction of the wind on the surface.[81]

This acceleration of the current takes place in the direction of waves and dominant wind. Accordingly, when the ocean depth increases, the rotation of the earth changes the direction of currents in proportion with the increase of depth, while friction lowers their speed. At a certain ocean depth, the current changes direction and is seen inverted in the opposite direction with current speed becoming null: known as the Ekman spiral. The influence of these currents is mainly experienced at the mixed layer of the ocean surface, often from 400 to 800 meters of maximum depth. These currents can considerably change and are dependent on the yearly seasons. If the mixed layer is less thick (10 to 20 meters), the quasi-permanent current at the surface can adopt quite a different direction in relation to the direction of the wind. In this case, the water column becomes virtually homogeneous above the thermocline.[81]

The wind blowing on the ocean surface will set the water in motion. The global pattern of winds (also called atmospheric circulation) creates a global pattern of ocean currents. These are not only driven by the wind but also by the effect of the circulation of the earth (coriolis force). Theses major ocean currents include the Gulf Stream, Kuroshio current, Agulhas current and Antarctic Circumpolar Current. The Antarctic Circumpolar Current encircles Antarctica and influences the area's climate as well as connecting currents in several oceans.[81]

Relationship of currents and climate

Main article: Atlantic meridional overturning circulation

Map of the Gulf Stream, a major ocean current that transports heat from the equator to northern latitudes and moderates the climate of Europe.
Map of the Gulf Stream, a major ocean current that transports heat from the equator to northern latitudes and moderates the climate of Europe.

Collectively, currents move enormous amounts of water and heat around the globe influencing climate. These wind driven currents are largely confined to the top hundreds of meters of the ocean. At greater depth the drivers of water motion are the thermohaline circulation (the Atlantic meridional overturning circulation (AMOC) is part of a global thermoholine circulation). This is driven by the cooling of surface waters at northern and southern polar latitudes creating dense water which sinks to the bottom of the ocean. This cold and dense water moves slowly away from the poles which is why the waters in the deepest layers of the world ocean are so cold. This deep ocean water circulation is relatively slow and water at the bottom of the ocean can be isolated from the ocean surface and atmosphere for hundreds or even a few thousand years.[81] This circulation has important impacts on global climate and the uptake and redistribution of pollutants such as carbon dioxide by moving these contaminants from the surface into the deep ocean.

Ocean currents greatly affect Earth's climate by transferring heat from the tropics to the polar regions and thereby also affecting air temperature and precipitation in coastal regions and further inland. Surface heat and freshwater fluxes create global density gradients that drive the thermohaline circulation part of large-scale ocean circulation. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation.

Oceans moderate the climate of locations where prevailing winds blow in from the ocean. At similar latitudes, a place on Earth with more influence from the ocean will have a more moderate climate than a place with more influence from land. For example, the cities San Francisco (37.8 N) and New York (40.7 N) have different climates because San Francisco has more influence from the ocean. San Francisco, on the west coast of North America, gets winds from the west over the Pacific Ocean, and the influence of the ocean water yields a more moderate climate with a warmer winter and a longer, cooler summer, with the warmest temperatures happening later in the year. New York, on the east coast of North America gets winds from the west over land, so New York has colder winters and hotter, earlier summers than San Francisco.

Warmer ocean currents yield warmer climates in the long term, even at high latitudes. At similar latitudes, a place influenced by warm ocean currents will have a warmer climate overall than a place influenced by cold ocean currents. French Riviera (43.5 N) and Rockland, Maine (44.1 N) have same latitude, but the French Riviera is influenced by warm waters transported by the Gulf Stream into the Mediterranean Sea and has a warmer climate overall. Maine is influenced by cold waters transported south by the Labrador Current giving it a colder climate overall.

Changes in the thermohaline circulation are thought to have significant impacts on Earth's energy budget. Since the thermohaline circulation governs the rate at which deep waters reach the surface, it may also significantly influence atmospheric carbon dioxide concentrations. Modern observations, climate simulations and paleoclimate reconstructions suggest that the Atlantic Meridional Overturning Circulation (AMOC) has weakened since the preindustrial era. The latest climate change projections in 2021 suggest that the AMOC is likely to weaken further over the 21st century.[82]: 19  Such a weakening could cause large changes to global climate, with the North Atlantic particularly vulnerable.[82]: 19 

Waves and swell

Movement of water as waves pass

Main articles: Wind wave and Swell (ocean)

The motions of the ocean surface, known as undulations or wind waves, are the partial and alternate rising and falling of the ocean surface. The series of mechanical waves that propagate along the interface between water and air is called swell – a term used in sailing, surfing and navigation.[83] These motions profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from sea sickness.

Wind blowing over the surface of a body of water forms waves that are perpendicular to the direction of the wind. The friction between air and water caused by a gentle breeze on a pond causes ripples to form. A strong blow over the ocean causes larger waves as the moving air pushes against the raised ridges of water. The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in the Southern Hemisphere in the Roaring Forties, long, organized masses of water called swell roll across the ocean.[84]: 83–84 [39][85] If the wind dies down, the wave formation is reduced, but already-formed waves continue to travel in their original direction until they meet land. The size of the waves depends on the fetch, the distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between the two can produce broken, irregular seas.[39]

Constructive interference can cause individual (unexpected) rogue waves much higher than normal.[86] Most waves are less than 3 m (10 ft) high[86] and it is not unusual for strong storms to double or triple that height.[87] Rogue waves, however, have been documented at heights above 25 meters (82 ft).[88][89]

The top of a wave is known as the crest, the lowest point between waves is the trough and the distance between the crests is the wavelength. The wave is pushed across the surface of the ocean by the wind, but this represents a transfer of energy and not a horizontal movement of water. As waves approach land and move into shallow water, they change their behavior. If approaching at an angle, waves may bend (refraction) or wrap around rocks and headlands (diffraction). When the wave reaches a point where its deepest oscillations of the water contact the ocean floor, they begin to slow down. This pulls the crests closer together and increases the waves' height, which is called wave shoaling. When the ratio of the wave's height to the water depth increases above a certain limit, it "breaks", toppling over in a mass of foaming water.[86] This rushes in a sheet up the beach before retreating into the ocean under the influence of gravity.[90]

Earthquakes, volcanic eruptions or other major geological disturbances can set off waves that can lead to tsunamis in coastal areas which can be very dangerous.[91][92]


Main article: Tide

High tide and low tide in the Bay of Fundy, Canada.
High tide and low tide in the Bay of Fundy, Canada.

Tides are the regular rise and fall in water level experienced by oceans in response to the gravitational influences of the moon and the sun, and the effects of the Earth's rotation. During each tidal cycle, at any given place the water rises to a maximum height known as "high tide" before ebbing away again to the minimum "low tide" level. As the water recedes, it uncovers more and more of the foreshore, also known as the intertidal zone. The difference in height between the high tide and low tide is known as the tidal range or tidal amplitude.[93][94]

In the open ocean tidal ranges are less than 1 meter, but in coastal areas these tidal ranges increase to more than 10 meters in some areas.[95] Some of the largest tidal ranges in the world occur in the Bay of Fundy and Ungava Bay in Canada, reaching up to 16 meters.[96] Other locations with record high tidal ranges include the Bristol Channel between England and Wales, Cook Inlet in Alaska, and the Río Gallegos in Argentina.[97]

Most places experience two high tides each day, occurring at intervals of about 12 hours and 25 minutes. This is half the 24 hours and 50 minute period that it takes for the Earth to make a complete revolution and return the moon to its previous position relative to an observer. Tidal force or tide-raising force decreases rapidly with distance, so the moon has more than twice as great an effect on tides as the Sun.[98] When the sun, moon and Earth are all aligned (full moon and new moon), the combined effect results in the high "spring tides".[93] A storm surge can occur when high winds pile water up against the coast in a shallow area and this, coupled with a low pressure system, can raise the surface of the ocean at high tide dramatically.

Water cycle, weather and rainfall

Further information: Effects of climate change on the water cycle and Water distribution on Earth

The ocean is a major driver of Earth's water cycle.
The ocean is a major driver of Earth's water cycle.

Ocean water represents the largest body of water within the global water cycle (oceans contain 97% of Earth's water). Evaporation from the ocean moves water into the atmosphere to later rain back down onto land and the ocean.[99] Oceans have a significant effect on the biosphere. The ocean as a whole is thought to cover approximately 90% of the Earth's biosphere.[54] Oceanic evaporation, as a phase of the water cycle, is the source of most rainfall (about 90%),[99] causing a global cloud cover of 67% and a consistent oceanic cloud cover of 72%.[100] Ocean temperatures affect climate and wind patterns that affect life on land. One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where the system forms).

As the world's ocean is the principal component of Earth's hydrosphere, it is integral to life on Earth, forms part of the carbon cycle and water cycle, and – as a huge heat reservoir – influences climate and weather patterns.

Chemical composition of seawater

Main article: Seawater § Properties


Further information: Salinity § Seawater, and Seawater § Salinity

Annual mean sea surface salinity in practical salinity units (psu) from the World Ocean Atlas.[101]
Annual mean sea surface salinity in practical salinity units (psu) from the World Ocean Atlas.[101]

Salinity is a measure of the total amounts of dissolved salts in seawater. It was originally measured via measurement of the amount of chloride in seawater and hence termed chlorinity. It is now routinely measured by measuring electrical conductivity of the water sample. Salinity can be calculated using the chlorinity, which is a measure of the total mass of halogen ions (includes fluorine, chlorine, bromine, and iodine) in seawater. By international agreement, the following formula is used to determine salinity:[102]

Salinity (in ‰) = 1.80655 × Chlorinity (in ‰)

The average ocean water chlorinity is about 19.2‰, and, thus, the average salinity is around 34.7‰.[102]

Salinity has a major influence on the density of seawater. A zone of rapid salinity increase with depth is called a halocline. The temperature of maximum density of seawater decreases as its salt content increases. Freezing temperature of water decreases with salinity, and boiling temperature of water increases with salinity. Typical seawater freezes at around −2 °C at atmospheric pressure.[103]

Salinity is higher in Earth's oceans where there is more evaporation and lower where there is more precipitation. If precipitation exceeds evaporation, as is the case in polar and some temperate regions, salinity will be lower. If evaporation exceeds precipitation, as is sometimes the case in tropical regions, salinity will be higher. For example, evaporation is greater than precipitation in the Mediterranean Sea, which has an average salinity of 38‰, more saline than the global average of 34.7‰.[104] Thus, oceanic waters in polar regions have lower salinity content than oceanic waters tropical regions.[102] However, when sea ice forms at high latitudes, salt is excluded from the ice as it forms, which can increase the salinity in the residual seawater in polar regions such as the Arctic Ocean.[69] [105]

Observations of sea surface salinity between 1950 to 2019 indicate that due to the effects of climate change on oceans regions of high salinity and evaporation have become more saline, while regions of low salinity and more precipitation have become fresher.[106] It is very likely that the Pacific and Southern Oceans have freshened while the Atlantic has become more saline.[106]

General characteristics of ocean surface waters

The waters in different regions of the ocean have quite different temperature and salinity characteristics. This is due to differences in the local water balance (precipitation vs. evaporation) and the "sea to air" temperature gradients. These characteristics can vary widely among ocean regions. The table below provides an illustration of the sort of values usually encountered.

General characteristics of ocean surface waters by region[107][108][109][110][111]
Characteristic Polar regions Temperate regions Tropical regions
Precipitation vs. evaporation Precip > Evap Precip > Evap Evap > Precip
Sea surface temperature in winter −2 °C 5 to 20 °C 20 to 25 °C
Average salinity 28‰ to 32‰ 35‰ 35‰ to 37‰
Annual variation of air temperature ≤ 40 °C 10 °C < 5 °C
Annual variation of water temperature < 5 °C 10 °C < 5 °C

Dissolved gases

Sea surface oxygen concentration in moles per cubic meter from the World Ocean Atlas.[112]
Sea surface oxygen concentration in moles per cubic meter from the World Ocean Atlas.[112]

Ocean water contains large quantities of dissolved gases, including oxygen, carbon dioxide and nitrogen. These dissolve into ocean water via gas exchange at the ocean surface, with the solubility of these gases depending on the temperature and salinity of the water.[8] The four most abundant gases in earth’s atmosphere and oceans are nitrogen, oxygen, argon, and carbon dioxide. In the ocean by volume, the most abundant gases dissolved in seawater are carbon dioxide (including bicarbonate and carbonate ions, 14 mL/L on average), nitrogen (9 mL/L), and oxygen (5 mL/L) at equilibrium at 24 °C (75 °F) [113] [114] [115] All gases are more soluble – more easily dissolved – in colder water than in warmer water. For example, when salinity and pressure are held constant, oxygen concentration in water almost doubles when the temperature drops from that of a warm summer day 30 °C (86 °F) to freezing 0 °C (32 °F). Similarly, carbon dioxide and nitrogen gases are more soluble at colder temperatures, and their solubility changes with temperature at different rates. [113] [116]

Oxygen, photosynthesis and carbon cycling

Further information: Marine biogeochemical cycles, Ocean deoxygenation, Oceanic carbon cycle, and Biological pump

Diagram of the ocean carbon cycle showing the relative size of stocks (storage) and fluxes. [117]
Diagram of the ocean carbon cycle showing the relative size of stocks (storage) and fluxes. [117]

The process of photosynthesis in the surface ocean releases oxygen and consumes carbon dioxide. This photosynthesis in the ocean is dominated by phytoplankton, microscopic free floating algae. After the plants grow, bacterial decomposition of the organic matter formed by photosynthesis in the ocean consumes oxygen and releases carbon dioxide. The sinking and bacterial decomposition of some organic matter in deep ocean water, at depths where the waters are out of contact with the atmosphere, leads to a reduction in oxygen concentrations and increase in carbon dioxide, carbonate and bicarbonate.[118] This cycling of carbon dioxide in oceans is an important part of the global carbon cycle.

The increasing carbon dioxide concentrations in the atmosphere due to fossil fuel combustion lead to higher concentrations in the ocean waters and ocean acidification.[9] Dissolving atmospheric carbon dioxide reacts with bicarbonate and carbonate ions in seawater to shift the chemical balance of the water, making it more acidic. The oceans represent a major sink for carbon dioxide taken up from the atmosphere by photosynthesis and by dissolution. There is also increasing attention focused on carbon dioxide uptake in coastal marine habitats such as mangroves and saltmarshes, a process sometimes referred to as “Blue carbon”. Attention is focused on these ecosystems because they are strong carbon sinks as well as ecologically important habitats under considerable threat from human activities and environmental degradation.

As deep ocean water circulates throughout the globe, it contains gradually less oxygen and gradually more carbon dioxide with more time away from the air at the surface. This gradual decrease in oxygen concentration happens as sinking organic matter continuously gets decomposed during the time the water is out of contact with the atmosphere.[118] Most of the deep waters of the ocean still contain relatively high concentrations of oxygen sufficient for most animals to survive. However, some ocean areas have very low oxygen due to long periods of isolation of the water from the atmosphere. These oxygen deficient areas, called oxygen minimum zones or hypoxic waters, could be made worse by the effects of climate change on oceans.[119]

Residence times of chemical elements and ions

Residence time of elements in the ocean depends on supply by processes like rock weathering and rivers vs. removal by processes like evaporation and sedimentation.
Residence time of elements in the ocean depends on supply by processes like rock weathering and rivers vs. removal by processes like evaporation and sedimentation.

The ocean waters contain many chemical elements as dissolved ions. Elements dissolved in ocean waters have a wide range of concentrations. Some elements have very high concentrations of several grams per liter, such as sodium and chloride, together making up the majority of ocean salts. Other elements, such as iron, are present at tiny concentrations of just a few nanograms (10−9 grams) per liter.[102]

The concentration of any element depends on its rate of supply to the ocean and its rate of removal. Elements enter the ocean from rivers, the atmosphere and hydrothermal vents. Elements are removed from ocean water by sinking and becoming buried in sediments or evaporating to the atmosphere in the case of water and some gases. Oceanographers consider the balance of input and removal by estimating the residence time of an element. Residence time is the average time the element would spend dissolved in the ocean before it is removed. Very abundant elements in ocean water like sodium have high rates of input, reflecting high abundance in rocks and relatively rapid rock weathering, coupled to very slow removal from the ocean because sodium ions are rather unreactive and very soluble. In contrast, other elements such as iron and aluminium are abundant in rocks but very insoluble, meaning that inputs to the ocean are low and removal is rapid. These cycles represent part of the major global cycle of elements that has gone on since the Earth first formed. The residence times of the very abundant elements in the ocean are estimated to be millions of years, while for highly reactive and insoluble elements, residence times are only hundreds of years.[102]

Residence times of elements and ions[120][121]
Chemical element or ion Residence time (years)
Chloride (Cl) 100,000,000
Sodium (Na+) 68,000,000
Magnesium (Mg2+) 13,000,000
Potassium (K+) 12,000,000
Sulfate (SO42−) 11,000,000
Calcium (Ca2+) 1,000,000
Carbonate (CO32−) 110,000
Silicon (Si) 20,000
Water (H2O) 4,100
Manganese (Mn) 1,300
Aluminum (Al) 600
Iron (Fe) 200


See also: Eutrophication § Coastal waters

A few elements such as nitrogen, phosphorus, iron, and potassium are essential for life, are major components of biological material, and are commonly called “nutrients”. Nitrate and phosphate have ocean residence times of 10,000[122] and 69,000 [123]years, respectively, while potassium is a much more abundant ion in the ocean with a residence time of 12 million[124] years. The biological cycling of these elements means that this represents a continuous removal process from the ocean's water column as degrading organic material sinks to the ocean floor as sediment.

Phosphate from intensive agriculture and untreated sewage is transported via runoff to rivers and coastal zones to the ocean where it is metabolized. Eventually, it sinks to the ocean floor and is no longer available to humans as a commercial resource.[125] Production of rock phosphate, an essential ingredient in inorganic fertilizer[126] is a slow geological process occurring in some of the world's ocean sediments thus making minable sedimentary apatite (phosphate) in effect a non-renewable resource (see peak phosphorus). This continuous net deposition loss of non-renewable phosphate from human activities may become a resource problem in the future for fertilizer production and food security.[127][128]

Climate change

There are many significant effects of climate change on oceans including: an increase in sea surface temperature as well as ocean temperatures at greater depths, more frequent marine heatwaves, a reduction in pH value, a rise in sea level from ocean warming and ice sheet melting, sea ice decline in the Arctic, increased upper ocean stratification, reductions in oxygen levels, increased contrasts in salinity (salty areas becoming saltier and fresher areas becoming less salty),[129] changes to ocean currents including a weakening of the Atlantic meridional overturning circulation, and stronger tropical cyclones and monsoons.[71] All these changes have knock-on effects which disturb marine ecosystems. The root cause of these observed changes is the Earth warming due to anthropogenic emissions of greenhouse gases, such as for example carbon dioxide and methane. This leads inevitably to ocean warming, because the ocean is taking up most of the additional heat in the climate system.[130] Some of the additional carbon dioxide in the atmosphere is taken up by the ocean (via carbon sequestration), which leads to ocean acidification of the ocean water.[131] It is estimated that the ocean takes up roughly a quarter of total anthropogenic CO2 emissions.[131]

Warming of the ocean surface due to higher air temperatures leads to increased ocean temperature stratification.[74]: 471  The decline in mixing of the ocean layers stabilises warm water near the surface while reducing cold, deep water circulation. The reduced up and down mixing reduces the ability of the ocean to absorb heat, directing a larger fraction of future warming toward the atmosphere and land. Energy available for tropical cyclones and other storms is expected to increase, nutrients for fish in the upper ocean layers are set to decrease, as is the capacity of the oceans to store carbon.[132]

Warmer water cannot contain as much oxygen as cold water. As a result, the gas exchange equilibrium changes to reduce ocean oxygen levels and increase oxygen in the atmosphere. Increased thermal stratification may lead to reduced supply of oxygen from the surface waters to deeper waters, and therefore further decrease the water's oxygen content.[133] The ocean has already lost oxygen throughout the water column, and oxygen minimum zones are expanding worldwide.[74]: 471 

These changes disturb marine ecosystems, which can cause both extinctions and population explosions, change the distribution of species,[71] and impact coastal fishing and tourism. Increase of water temperature will also have a devastating effect on various oceanic ecosystems, such as coral reefs. The direct effect is the coral bleaching of these reefs, which live within a narrow temperature margin, so a small increase in temperature would have a drastic effect in these environments. Ocean acidification and temperature rise will also affect the productivity and distribution of species within the ocean, threatening fisheries and disrupting marine ecosystems. Loss of sea ice habitats due to warming will severely impact the many polar species which depend on this sea ice. Many of these climate change pressures interact, compounding the pressures on the climate system and on ocean ecosystems.[71]

Marine life

Main articles: Marine life, Marine habitats, Marine primary production, Marine biology, and Marine ecosystem

Life within the ocean evolved 3 billion years prior to life on land. Both the depth and the distance from shore strongly influence the biodiversity of the plants and animals present in each region.[134] The diversity of life in the ocean is immense, including:

Killer whales (orcas) are highly visible marine apex predators that hunt many large species. But most biological activity in the ocean takes place with microscopic marine organisms that cannot be seen individually with the naked eye, such as marine bacteria and phytoplankton.[135]
Killer whales (orcas) are highly visible marine apex predators that hunt many large species. But most biological activity in the ocean takes place with microscopic marine organisms that cannot be seen individually with the naked eye, such as marine bacteria and phytoplankton.[135]

Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon. Marine life in part shape and protect shorelines, and some marine organisms even help create new land (e.g. coral building reefs).

More than 200,000 marine species have been documented, and perhaps two million marine species are yet to be documented.[136] Marine species range in size from the microscopic like phytoplankton, which can be as small as 0.02 micrometres, to huge cetaceans like the blue whale – the largest known animal, reaching 33 m (108 ft) in length.[137][138] Marine microorganisms, including protists and bacteria and their associated viruses, have been variously estimated as constituting about 70% [139] or about 90% [140][135] of the total marine biomass. Marine life is studied scientifically in both marine biology and in biological oceanography. The term marine comes from the Latin mare, meaning "sea" or "ocean".
Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term marine comes from the Latin mare, meaning sea or ocean). A habitat is an ecological or environmental area inhabited by one or more living species.[141] The marine environment supports many kinds of these habitats. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf.
Coral reefs form complex marine ecosystems with tremendous biodiversity
Coral reefs form complex marine ecosystems with tremendous biodiversity
Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply[142][143] and 90% of habitable space on Earth.[144] Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems.[145] Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.

Human uses of the oceans

Main articles: Sea § Humans and the sea, and Sea in culture

The ocean has been linked to human activity throughout history. These activities serve a wide variety of purposes, including navigation and exploration, naval warfare, travel, shipping and trade, food production (e.g. fishing, whaling, seaweed farming, aquaculture), leisure (cruising, sailing, recreational boat fishing, scuba diving), power generation (see marine energy and offshore wind power), extractive industries (offshore drilling and deep sea mining), freshwater production via desalination.

Many of the world's goods are moved by ship between the world's seaports.[146] Large quantities of goods are transported across the ocean, especially across the Atlantic and around the Pacific Rim.[147] A lot of cargo, such as manufactured goods, is usually transported within standard sized, lockable containers, loaded on purpose-built container ships at dedicated terminals.[148] Containerization greatly increased the efficiency and decreased the cost of moving goods by sea, and was a major factor leading to the rise of globalization and exponential increases in international trade in the mid-to-late 20th century.[149]

Oceans are also the major supply source for the fishing industry. Some of the major harvests are shrimp, fish, crabs, and lobster.[54] The biggest commercial fishery globally is for anchovies, Alaska pollock and tuna.[150]: 6  A report by FAO in 2020 stated that "in 2017, 34 percent of the fish stocks of the world’s marine fisheries were classified as overfished".[150]: 54  Fish and other fishery products from both wild fisheries and aquaculture are among the most widely consumed sources of protein and other essential nutrients. Data in 2017 showed that "fish consumption accounted for 17 percent of the global population’s intake of animal proteins".[150] In order to fulfill this need, coastal countries have exploited marine resources in their exclusive economic zone, although fishing vessels are increasingly venturing further afield to exploit stocks in international waters.[151]

The ocean offers a very large supply of energy carried by ocean waves, tides, salinity differences, and ocean temperature differences which can be harnessed to generate electricity.[152] Forms of sustainable marine energy include tidal power, ocean thermal energy and wave power.[152][153] Offshore wind power is captured by wind turbines placed out on the ocean; it has the advantage that wind speeds are higher than on land, though wind farms are more costly to construct offshore.[154] There are large deposits of petroleum, as oil and natural gas, in rocks beneath the ocean floor. Offshore platforms and drilling rigs extract the oil or gas and store it for transport to land.[155]

"Freedom of the seas" is a principle in international law dating from the seventeenth century. It stresses freedom to navigate the oceans and disapproves of war fought in international waters.[156] Today, this concept is enshrined in the United Nations Convention on the Law of the Sea (UNCLOS).[156]

There are two major international legal organizations that are involved in ocean governance on a global scale, namely the International Maritime Organization and the United Nations. The International Maritime Organization (IMO), which was ratified in 1958 is responsible mainly for maritime safety, liability and compensation and they have held some conventions on marine pollution related to shipping incidents. Ocean governance is the conduct of the policy, actions and affairs regarding the world's oceans.[157]

Threats from human activities

Global cumulative human impact on the ocean[158]
Global cumulative human impact on the ocean[158]

Further information: Human impact on marine life

Human activities affect marine life and marine habitats through many negative influences, such as marine pollution (including marine debris and microplastics) overfishing, ocean acidification and other effects of climate change on oceans.

Marine pollution

Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well.[159] Since most inputs come from land, either via the rivers, sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides or dust particles into the ocean.[160] The pollution often comes from nonpoint sources such as agricultural runoff, wind-blown debris, and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans.[161] Pathways of pollution include direct discharge, land runoff, ship pollution, atmospheric pollution and, potentially, deep sea mining.

The types of marine pollution can be grouped as pollution from marine debris, plastic pollution, including microplastics, ocean acidification, nutrient pollution, toxins and underwater noise. Plastic pollution in the ocean is a type of marine pollution by plastics, ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Plastic pollution is harmful to marine life.

Plastic pollution

Marine plastic pollution (or plastic pollution in the ocean) is a type of marine pollution by plastics, ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic.[162][163] Microplastics and nanoplastics result from the breakdown or photodegradation of plastic waste in surface waters, rivers or oceans. Recently, scientists have uncovered nanoplastics in heavy snow, more specifically about 3000 tons that cover Switzerland yearly.[164] It is estimated that there is a stock of 86 million tons of plastic marine debris in the worldwide ocean as of the end of 2013, assuming that 1.4% of global plastics produced from 1950 to 2013 has entered the ocean and has accumulated there.[165] It is estimated that 19–23 million tonnes of plastic leaks into aquatic ecosystems annually.[166] The 2017 United Nations Ocean Conference estimated that the oceans might contain more weight in plastics than fish by the year 2050.[167]

A woman and a boy collecting plastic waste at a beach during a cleanup exercise
Oceans are polluted by plastic particles ranging in size from large original material such as bottles and bags, down to microplastics formed from the fragmentation of plastic material. This material is only very slowly degraded or removed from the ocean so plastic particles are now widespread throughout the surface ocean and are known to be having deleterious effects on marine life.[168] Discarded plastic bags, six pack rings, cigarette butts and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries.[169] Aquatic life can be threatened through entanglement, suffocation, and ingestion.[170][171][172] Fishing nets, usually made of plastic, can be left or lost in the ocean by fishermen. Known as ghost nets, these entangle fish, dolphins, sea turtles, sharks, dugongs, crocodiles, seabirds, crabs, and other creatures, restricting movement, causing starvation, laceration, infection, and, in those that need to return to the surface to breathe, suffocation.[173] There are various types of ocean plastics causing problems to marine life. Bottle caps have been found in the stomachs of turtles and seabirds, which have died because of the obstruction of their respiratory and digestive tracts.[174] Ghost nets are also a problematic type of ocean plastic as they can continuously trap marine life in a process known as "ghost fishing".[175]


Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area. Overfishing can occur in water bodies of any sizes, such as ponds, wetlands, rivers, lakes or oceans, and can result in resource depletion, reduced biological growth rates and low biomass levels. Sustained overfishing can lead to critical depensation, where the fish population is no longer able to sustain itself. Some forms of overfishing, such as the overfishing of sharks, has led to the upset of entire marine ecosystems.[176] Types of overfishing include: growth overfishing, recruitment overfishing, ecosystem overfishing.


Main articles: Marine conservation and marine protected area

Protecting Earth's oceans ecosystem/s against its recognized threats is a major component of environmental protection and is closely related to sustainable development. One of its main techniques is the creation and enforcement of marine protected areas (MPAs). Other techniques may include standardized product certifications, supply chain transparency requirements policies, policies to prevent marine pollution, eco-tariffs, research and development,[177] ecosystem-assistance (e.g. for coral reefs), support for sustainable seafood (e.g. sustainable fishing practices and types of aquaculture), banning and systematically obstructing (e.g. via higher costs policies) unsustainable ocean use and associated industries (e.g. cruise ship travel, certain shipping practices), monitoring, revising waste management of plastics and fashion industry pollutants, protection of marine resources and components whose extraction or disturbance would cause substantial harm, engagement of broader publics and impacted communities,[178] novel decision-making mechanisms,[179] and the development of ocean clean-up projects. Ocean protection serves to i.a. protect human health and to safeguard stable conditions of this natural ecosystem upon which humans depend.[180][181][additional citation(s) needed]

It may be necessary to consider marine protection within a national, regional and international context.[182] Marine protection could also have synergistic effects – for instance, according to a study, a global network of MPAs designed to improve fisheries productivity could substantially increase future catch.[183]

In 2021, 43 expert scientists published the first scientific framework version that – via integration, review, clarifications and standardization – enables the evaluation of levels of protection of marine protected areas and can serve as a guide for any subsequent efforts to improve, plan and monitor marine protection quality and extents. Examples are the efforts towards the 30%-protection-goal of the "Global Deal For Nature"[184] and the UN's Sustainable Development Goal 14 ("life below water").[185][186]

Extraterrestrial oceans

Main articles: Planetary oceanography, Extraterrestrial liquid water, and Ocean world

Further information: List of largest lakes and seas in the Solar System

Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, which are made of hydrocarbons instead of water. However, there is strong evidence for subsurface water oceans' existence elsewhere in the Solar System. The best-established candidates for subsurface water oceans in the Solar System are Jupiter's moons Europa, Ganymede, and Callisto; and Saturn's moons Enceladus and Titan.[187]

Although Earth is the only known planet with large stable bodies of liquid water on its surface and the only one in the Solar System, other celestial bodies are thought to have large oceans.[188] In June 2020, NASA scientists reported that it is likely that exoplanets with oceans may be common in the Milky Way galaxy, based on mathematical modeling studies.[189][190]

Supercritical fluid on gas giants

The inner structure of gas giants remain poorly understood. Scientists suspect that, under extreme pressure, hydrogen would act as a supercritical fluid, hence the likelihood of "oceans" of liquid hydrogen deep in the interior of gas giants like Jupiter.[191][192]

Oceans of liquid carbon have been hypothesized to exist on ice giants, notably Neptune and Uranus.[193][194]

See also


  1. ^ a b "8(o) Introduction to the Oceans".
  2. ^ "Ocean." Dictionary, Merriam-Webster, Accessed March 14, 2021.
  3. ^ a b "ocean, n". Oxford English Dictionary. Retrieved February 5, 2012.
  4. ^ a b "ocean". Merriam-Webster. Retrieved February 6, 2012.
  5. ^ "How much oxygen comes from the ocean?". National Ocean Service. National Oceanic and Atmospheric Administration U.S. Department of Commerce. February 26, 2021. Retrieved November 3, 2021.
  6. ^ a b Gordon, Arnold (2004). "Ocean Circulation". The Climate System. Columbia University. Retrieved July 6, 2013.
  7. ^ a b NOAA, NOAA. "What is a current?". Ocean Service Noaa. National Ocean Service. Retrieved December 13, 2020.
  8. ^ a b Chester, R.; Jickells, Tim (2012). "Chapter 8: Air–sea gas exchange". Marine geochemistry (3rd ed.). Chichester, West Sussex, UK: Wiley/Blackwell. ISBN 978-1-118-34909-0. OCLC 781078031.
  9. ^ a b IUCN (2017) THE OCEAN AND CLIMATE CHANGE, IUCN (International Union for Conservation of Nature) Issues Brief.
  10. ^ Drogin, Bob (August 2, 2009). "Mapping an ocean of species". Los Angeles Times. Retrieved August 18, 2009.
  11. ^ "Sea". Retrieved March 13, 2013.
  12. ^ Bromhead, Helen, Landscape and Culture – Cross-linguistic Perspectives, p. 92, John Benjamins Publishing Company, 2018, ISBN 9027264007, 9789027264008; unlike Americans, speakers of British English do not go swimming in "the ocean" but always "the sea".
  13. ^ "WordNet Search — sea". Princeton University. Retrieved February 21, 2012.
  14. ^ "What's the difference between an ocean and a sea?". Ocean facts. National Oceanic and Atmospheric Administration. Retrieved April 19, 2013.
  15. ^ a b Janin, H.; Mandia, S.A. (2012). Rising Sea Levels: An Introduction to Cause and Impact. McFarland, Incorporated, Publishers. p. 20. ISBN 978-0-7864-5956-8. Retrieved August 26, 2022.
  16. ^ Bruckner, Lynne and Dan Brayton (2011). Ecocritical Shakespeare (Literary and Scientific Cultures of Early Modernity). Ashgate Publishing, Ltd. ISBN 978-0754669197.
  17. ^ a b Ro, Christine (February 3, 2020). "Is It Ocean Or Oceans?". Forbes. Retrieved August 26, 2022.
  18. ^ "Ocean". Retrieved November 8, 2012.
  19. ^ a b ""Distribution of land and water on the planet". UN Atlas of the Oceans. Archived from the original on March 3, 2016.
  20. ^ Spilhaus, Athelstan F. (July 1942). "Maps of the whole world ocean". Geographical Review. 32 (3): 431–5. doi:10.2307/210385. JSTOR 210385.
  21. ^ Ὠκεανός, Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus project
  22. ^ Matasović, Ranko, A Reader in Comparative Indo-European Religion Zagreb: Univ of Zagreb, 2016. p. 20.
  23. ^ "Why do we have an ocean?". NOAA's National Ocean Service. June 1, 2013. Retrieved September 3, 2022.
  24. ^ "NASA Astrobiology". Astrobiology. June 5, 2017. Retrieved September 13, 2022.
  25. ^ a b Pinti, Daniele L.; Arndt, Nicholas (2014), "Oceans, Origin of", Encyclopedia of Astrobiology, Springer Berlin Heidelberg, pp. 1–5, doi:10.1007/978-3-642-27833-4_1098-4, ISBN 9783642278334
  26. ^ Cates, N.L.; Mojzsis, S.J. (March 2007). "Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq supracrustal belt, northern Québec". Earth and Planetary Science Letters. 255 (1–2): 9–21. Bibcode:2007E&PSL.255....9C. doi:10.1016/j.epsl.2006.11.034. ISSN 0012-821X.
  27. ^ O'Neil, Jonathan; Carlson, Richard W.; Paquette, Jean-Louis; Francis, Don (November 2012). "Formation age and metamorphic history of the Nuvvuagittuq Greenstone Belt" (PDF). Precambrian Research. 220–221: 23–44. Bibcode:2012PreR..220...23O. doi:10.1016/j.precamres.2012.07.009. ISSN 0301-9268.
  28. ^ Washington University in St. Louis (August 27, 2020). "Meteorite study suggests Earth may have been wet since it formed - Enstatite chondrite meteorites, once considered 'dry,' contain enough water to fill the oceans -- and then some". EurekAlert!. Retrieved August 28, 2020.
  29. ^ American Association for the Advancement of Science (August 27, 2020). "Unexpected abundance of hydrogen in meteorites reveals the origin of Earth's water". EurekAlert!. Retrieved August 28, 2020.
  30. ^ Piani, Laurette; Marrocchi, Yves; Rigaudier, Thomas; Vacher, Lionel G.; Thomassin, Dorian; Marty, Bernard (2020). "Earth's water may have been inherited from material similar to enstatite chondrite meteorites". Science. 369 (6507): 1110–13. Bibcode:2020Sci...369.1110P. doi:10.1126/science.aba1948. ISSN 0036-8075. PMID 32855337. S2CID 221342529.
  31. ^ Guinan, E. F.; Ribas, I. (2002). Benjamin Montesinos, Alvaro Gimenez and Edward F. Guinan (ed.). Our Changing Sun: The Role of Solar Nuclear Evolution and Magnetic Activity on Earth's Atmosphere and Climate. ASP Conference Proceedings: The Evolving Sun and its Influence on Planetary Environments. San Francisco: Astronomical Society of the Pacific. Bibcode:2002ASPC..269...85G. ISBN 978-1-58381-109-2.
  32. ^ Staff (March 4, 2010). "Oldest measurement of Earth's magnetic field reveals battle between Sun and Earth for our atmosphere". Retrieved March 27, 2010.
  33. ^ a b Voosen, Paul (March 9, 2021). "Ancient Earth was a water world". Science. American Association for the Advancement of Science (AAAS). 371 (6534): 1088–1089. doi:10.1126/science.abh4289. ISSN 0036-8075. PMID 33707245. S2CID 241687784.
  34. ^ "The Water Cycle summary". USGS Water Science School. Archived from the original on January 16, 2018. Retrieved January 15, 2018.
  35. ^ Smith, Yvette (June 7, 2021). "Earth Is a Water World". NASA. Retrieved August 27, 2022.
  36. ^ "Water-Worlds". National Geographic Society. May 20, 2022. Retrieved August 24, 2022.
  37. ^ Lunine, Jonathan I. (2017). "Ocean worlds exploration". Acta Astronautica. Elsevier BV. 131: 123–130. Bibcode:2017AcAau.131..123L. doi:10.1016/j.actaastro.2016.11.017. ISSN 0094-5765.
  38. ^ "Ocean Worlds". Ocean Worlds. Retrieved August 27, 2022.
  39. ^ a b c d e "Volumes of the World's Oceans from ETOPO1". NOAA. Archived from the original on March 11, 2015. Retrieved March 7, 2015.((cite web)): CS1 maint: bot: original URL status unknown (link)
  40. ^ "Ocean-bearing Planets: Looking For Extraterrestrial Life In All The Right Places". Retrieved November 8, 2012.
  41. ^ "CIA World Factbook". CIA. Retrieved April 5, 2015.
  42. ^ Charette, Matthew; Smith, Walter H. F. (2010). "The volume of Earth's ocean". Oceanography. 23 (2): 112–114. doi:10.5670/oceanog.2010.51. Retrieved January 13, 2014.
  43. ^ World The World Factbook, CIA. Retrieved January 13, 2014.
  44. ^ a b "Recommendation ITU-R RS.1624: Sharing between the Earth exploration-satellite (passive) and airborne altimeters in the aeronautical radionavigation service in the band 4 200–4 400 MHz (Question ITU-R 229/7)" (PDF). ITU Radiotelecommunication Sector (ITU-R). Retrieved April 5, 2015. The oceans occupy about 3.35×108 km2 of area. There are 377412 km of oceanic coastlines in the world.
  45. ^ a b "Pacific Ocean". Encyclopedia of Earth. Retrieved March 7, 2015.
  46. ^ a b "Atlantic Ocean". Encyclopedia of Earth. Retrieved March 7, 2015.
  47. ^ a b "Indian Ocean". Encyclopedia of Earth. Retrieved March 7, 2015.
  48. ^ a b "Southern Ocean". Encyclopedia of Earth. Retrieved March 10, 2015.
  49. ^ a b "Limits of Oceans and Seas, 3rd edition" (PDF). International Hydrographic Organization. 1953. Archived from the original (PDF) on October 8, 2011. Retrieved December 28, 2020.
  50. ^ a b Tomczak, Matthias; Godfrey, J. Stuart (2003). Regional Oceanography: an Introduction (2 ed.). Delhi: Daya Publishing House. ISBN 978-81-7035-306-5. Archived from the original on June 30, 2007. Retrieved April 10, 2006.
  51. ^ a b Ostenso, Ned Allen. "Arctic Ocean". Encyclopædia Britannica. Retrieved July 2, 2012. As an approximation, the Arctic Ocean may be regarded as an estuary of the Atlantic Ocean.
  52. ^ a b "Arctic Ocean". Encyclopedia of Earth. Retrieved March 7, 2015.
  53. ^ "What is the longest mountain range on earth?". National Ocean Service. US Department of Commerce. Retrieved October 17, 2014.
  54. ^ a b c "NOAA – National Oceanic and Atmospheric Administration – Ocean". Retrieved February 16, 2020.
  55. ^ Drake, Michael J. (2005), "Origin of water in the terrestrial planets", Meteoritics & Planetary Science, 40 (4): 515–656, Bibcode:2005M&PS...40..515J, doi:10.1111/j.1945-5100.2005.tb00958.x.
  56. ^ Qadri, Syed (2003). "Volume of Earth's Oceans". The Physics Factbook. Retrieved June 7, 2007.
  57. ^ Charette, Matthew; Smith, Walter H. F. (2010). "The volume of Earth's ocean". Oceanography. 23 (2): 112–114. doi:10.5670/oceanog.2010.51. Retrieved September 27, 2012.
  58. ^ Where is Earth's water?, United States Geological Survey.
  59. ^ Eakins, B.W. and G.F. Sharman, Volumes of the World's Oceans from ETOPO1, NOAA National Geophysical Data Center, Boulder, CO, 2010.
  60. ^ Water in Crisis: Chapter 2, Peter H. Gleick, Oxford University Press, 1993.
  61. ^ World Water Resources: A New Appraisal and Assessment for the 21st Century (Report). UNESCO. 1998. Archived from the original on September 27, 2013. Retrieved June 13, 2013.
  62. ^ Kennish, Michael J. (2001). Practical handbook of marine science. Marine science series (3rd ed.). CRC Press. p. 35. ISBN 0-8493-2391-6.
  63. ^ Drazen, Jeffrey C. "Deep-Sea Fishes". School of Ocean and Earth Science and Technology, the University of Hawai'i at Mānoa. Archived from the original on May 24, 2012. Retrieved June 7, 2007.
  64. ^ "Scientists map Mariana Trench, deepest known section of ocean in the world". The Telegraph. Telegraph Media Group. December 7, 2011. Archived from the original on December 8, 2011. Retrieved March 23, 2012.
  65. ^ Fleming, Nic (May 27, 2015). "Is the sea really blue?". BBC - Earth. BBC. Retrieved August 25, 2021.
  66. ^ Webb, Paul (July 2020), "6.5 Light", Introduction to Oceanography, retrieved July 21, 2021
  67. ^ Morel, Andre; Prieur, Louis (1977). "Analysis of variations in ocean color 1". Limnology and Oceanography. 22 (4): 709–722. Bibcode:1977LimOc..22..709M. doi:10.4319/lo.1977.22.4.0709.
  68. ^ Coble, Paula G. (2007). "Marine Optical Biogeochemistry: The Chemistry of Ocean Color". Chemical Reviews. 107 (2): 402–418. doi:10.1021/cr050350+. PMID 17256912.
  69. ^ a b c d e f "Chapter 3. Physical Properties of Seawater". Descriptive physical oceanography : an introduction. Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift (6th ed.). Amsterdam: Academic Press. 2011. ISBN 978-0-7506-4552-2. OCLC 720651296.((cite book)): CS1 maint: others (link)
  70. ^ "What is a thermocline?". National Ocean Service. US Department of Commerce. Retrieved February 7, 2021.
  71. ^ a b c d "Summary for Policymakers". The Ocean and Cryosphere in a Changing Climate. 2022. pp. 3–36. doi:10.1017/9781009157964.001. ISBN 978-1-00-915796-4.
  72. ^ Gille, Sarah T. (February 15, 2002). "Warming of the Southern Ocean Since the 1950s". Science. 295 (5558): 1275–1277. Bibcode:2002Sci...295.1275G. doi:10.1126/science.1065863. PMID 11847337. S2CID 31434936.
  73. ^ Cheng, Lijing; Abraham, John; Zhu, Jiang; Trenberth, Kevin E.; Fasullo, John; Boyer, Tim; Locarnini, Ricardo; Zhang, Bin; Yu, Fujiang; Wan, Liying; Chen, Xingrong (February 2020). "Record-Setting Ocean Warmth Continued in 2019". Advances in Atmospheric Sciences. 37 (2): 137–142. Bibcode:2020AdAtS..37..137C. doi:10.1007/s00376-020-9283-7. S2CID 210157933.
  74. ^ a b c Bindoff, N.L., W.W.L. Cheung, J.G. Kairo, J. Arístegui, V.A. Guinder, R. Hallberg, N. Hilmi, N. Jiao, M.S. Karim, L. Levin, S. O’Donoghue, S.R. Purca Cuicapusa, B. Rinkevich, T. Suga, A. Tagliabue, and P. Williamson, 2019: Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press.
  75. ^ Jeffries, Martin O. (2012). "Sea ice". Encyclopedia Britannica. Britannica Online Encyclopedia. Retrieved April 21, 2013.
  76. ^ Wadhams, Peter (January 1, 2003). "How Does Arctic Sea Ice Form and Decay?". Arctic theme page. NOAA. Archived from the original on March 6, 2005. Retrieved April 25, 2005.
  77. ^ Weeks, Willy F. (2010). On Sea Ice. University of Alaska Press. p. 2. ISBN 978-1-60223-101-6.
  78. ^ Shokr, Mohammed; Sinha, Nirmal (2015). Sea Ice – Physics and Remote Sensing. John Wiley & Sons, Inc. ISBN 978-1119027898.
  79. ^ "Sea Ice". National Snow and Ice Data Center. Retrieved November 22, 2022.
  80. ^ "Tidal Currents – Currents: NOAA's National Ocean Service Education". National Ocean Service. US Department of Commerce. Retrieved February 7, 2021.
  81. ^ a b c d e "Chapter 7. Dynamical Processes for Descriptive Ocean Circulation". Descriptive physical oceanography : an introduction. Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift (6th ed.). Amsterdam: Academic Press. 2011. ISBN 978-0-7506-4552-2. OCLC 720651296.((cite book)): CS1 maint: others (link)
  82. ^ a b IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M.  Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA.
  83. ^ Observation of swell dissipation across oceans, F. Ardhuin, Collard, F., and B. Chapron, 2009: Geophys. Res. Lett. 36, L06607, doi:10.1029/2008GL037030
  84. ^ Stow, Dorrik (2004). Encyclopedia of the Oceans. Oxford University Press. ISBN 978-0-19-860687-1.
  85. ^ Young, I. R. (1999). Wind Generated Ocean Waves. Elsevier. p. 83. ISBN 978-0-08-043317-2.
  86. ^ a b c Garrison, Tom (2012). Essentials of Oceanography. 6th ed. pp. 204 ff. Brooks/Cole, Belmont. ISBN 0321814053.
  87. ^ National Meteorological Library and Archive (2010). "Fact Sheet 6—The Beaufort Scale". Met Office (Devon)
  88. ^ Holliday, N. P.; Yelland, M. J.; Pascal, R.; Swail, V. R.; Taylor, P. K.; Griffiths, C. R.; Kent, E. (2006). "Were extreme waves in the Rockall Trough the largest ever recorded?". Geophysical Research Letters. 33 (5): L05613. Bibcode:2006GeoRL..33.5613H. doi:10.1029/2005GL025238.
  89. ^ Laird, Anne (2006). "Observed Statistics of Extreme Waves". Naval Postgraduate School (Monterey).
  90. ^ "Ocean waves". Ocean Explorer. National Oceanic and Atmospheric Administration. Retrieved April 17, 2013.
  91. ^ "Life of a Tsunami". Tsunamis & Earthquakes. US Geological Survey. Retrieved July 14, 2021.
  92. ^ "Physics of Tsunamis". National Tsunami Warning Center of the USA. Retrieved July 14, 2021.
  93. ^ a b "Tides and Water Levels". NOAA Oceans and Coasts. NOAA Ocean Service Education. Retrieved April 20, 2013.
  94. ^ "Tidal amplitudes". University of Guelph. Retrieved September 12, 2013.
  95. ^ "Chapter 8. Gravity Waves, Tides, and Coastal Oceanography". Descriptive physical oceanography : an introduction. Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift (6th ed.). Amsterdam: Academic Press. 2011. ISBN 978-0-7506-4552-2. OCLC 720651296.((cite book)): CS1 maint: others (link)
  96. ^ "Weird Science: Extreme Tidal Ranges". Exploring Our Fluid Earth: Teaching Science as Inquiry. University of Hawaii. Retrieved November 9, 2021.
  97. ^ "Where are the Highest Tides in the World?". Casual Navigation. Retrieved November 9, 2021.
  98. ^ "Tides". Ocean Explorer. National Oceanic and Atmospheric Administration. Retrieved April 20, 2013.
  99. ^ a b "The Water Cycle: The Oceans". US Geological Survey. Retrieved July 17, 2021.
  100. ^ King, Michael D.; Platnick, Steven; Menzel, W. Paul; Ackerman, Steven A.; Hubanks, Paul A. (2013). "Spatial and Temporal Distribution of Clouds Observed by MODIS Onboard the Terra and Aqua Satellites". IEEE Transactions on Geoscience and Remote Sensing. Institute of Electrical and Electronics Engineers (IEEE). 51 (7): 3826–3852. Bibcode:2013ITGRS..51.3826K. doi:10.1109/tgrs.2012.2227333. ISSN 0196-2892. S2CID 206691291.
  101. ^ Baranova, Olga. "World Ocean Atlas 2009". National Centers for Environmental Information (NCEI). Retrieved January 18, 2022.
  102. ^ a b c d e Chester, R.; Jickells, Tim (2012). "Chapter 7: Descriptive oceanography: water-column parameters". Marine geochemistry (3rd ed.). Chichester, West Sussex, UK: Wiley/Blackwell. ISBN 978-1-118-34909-0. OCLC 781078031.
  103. ^ "Can the ocean freeze? Ocean water freezes at a lower temperature than freshwater". NOAA. Retrieved January 2, 2019.
  104. ^ "Hydrologic features and climate". Encyclopedia Britannica. Retrieved January 18, 2022.
  105. ^ "Salinity and Brine". National Snow and Ice Data Center. Retrieved January 18, 2022.
  106. ^ a b Fox-Kemper, B., H.T. Hewitt, C. Xiao, G. Aðalgeirsdóttir, S.S. Drijfhout, T.L. Edwards, N.R. Golledge, M. Hemer, R.E. Kopp, G.  Krinner, A. Mix, D. Notz, S. Nowicki, I.S. Nurhati, L. Ruiz, J.-B. Sallée, A.B.A. Slangen, and Y. Yu, 2021: Chapter 9: Ocean, Cryosphere and Sea Level Change. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L.  Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1211–1362, doi:10.1017/9781009157896.011.
  107. ^ "IPCC Fourth Assessment Report: Climate Change 2007, Working Group I: The Physical Science Basis, 5.6 Synthesis". IPCC (archive). Retrieved July 19, 2021.
  108. ^ "Evaporation minus precipitation, Latitude-Longitude, Annual mean". ERA-40 Atlas. ECMWF. Archived from the original on February 2, 2014.
  109. ^ Barry, Roger Graham; Chorley, Richard J. (2003). Atmosphere, Weather, and Climate. Routledge. p. 68. ISBN 9780203440513.
  110. ^ Deser, C.; Alexander, M. A.; Xie, S. P.; Phillips, A. S. (2010). "Sea Surface Temperature Variability: Patterns and Mechanisms" (PDF). Annual Review of Marine Science. 2: 115–43. Bibcode:2010ARMS....2..115D. doi:10.1146/annurev-marine-120408-151453. PMID 21141660. Archived from the original (PDF) on May 14, 2014.
  111. ^ Huang, Rui Xin (2010). Ocean circulation : wind-driven and thermohaline processes. Cambridge: Cambridge University Press. ISBN 978-0-511-68849-2. OCLC 664005236.
  112. ^ Garcia, H.E.; Locarnini, R.A.; Boyer, T.P.; Antonov, J.I. (2006). Levitus, S. (ed.). World Ocean Atlas 2005, Volume 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Oxygen Saturation. Washington, D.C: NOAA Atlas NESDIS 63, U.S. Government Printing Office. p. 342.
  113. ^ a b "The seawater solution". Seawater. Elsevier. 1995. pp. 85–127. doi:10.1016/b978-075063715-2/50007-1. ISBN 9780750637152.
  114. ^ "Dissolved Gases other than Carbon Dioxide in Seawater" (PDF). Retrieved May 5, 2014.
  115. ^ "Dissolved Oxygen and Carbon Dioxide" (PDF).
  116. ^ "12.742. Marine Chemistry. Lecture 8. Dissolved Gases and Air-sea exchange" (PDF). Retrieved May 5, 2014.
  117. ^ "Ocean carbon cycle". GRID-Arendal. June 5, 2009. Retrieved January 18, 2022.
  118. ^ a b Chester, R.; Jickells, Tim (2012). "Chapter 9: Nutrients oxygen organic carbon and the carbon cycle in seawater". Marine geochemistry (3rd ed.). Chichester, West Sussex, UK: Wiley/Blackwell. ISBN 978-1-118-34909-0. OCLC 781078031.
  119. ^ Breitburg, Denise; Levin, Lisa A.; Oschlies, Andreas; Grégoire, Marilaure; Chavez, Francisco P.; Conley, Daniel J.; Garçon, Véronique; Gilbert, Denis; Gutiérrez, Dimitri; Isensee, Kirsten; Jacinto, Gil S. (January 5, 2018). "Declining oxygen in the global ocean and coastal waters". Science. 359 (6371): eaam7240. Bibcode:2018Sci...359M7240B. doi:10.1126/science.aam7240. ISSN 0036-8075. PMID 29301986.
  120. ^ "Calculation of residence times in seawater of some important solutes" (PDF).
  121. ^ Chester, R.; Jickells, Tim (2012). "Chapter 11: Trace elements in the oceans". Marine geochemistry (3rd ed.). Chichester, West Sussex, UK: Wiley/Blackwell. ISBN 978-1-118-34909-0. OCLC 781078031.
  122. ^ "Monterey Bay Aquarium Research Institute".
  123. ^ "Monterey Bay Aquarium Research Institute".
  124. ^ "Potassium".
  125. ^ Paytan, Adina; McLaughlin, Karen (2007). "The Oceanic Phosphorus Cycle". Chemical Reviews. 107 (2): 563–576. doi:10.1021/cr0503613. ISSN 0009-2665. PMID 17256993. S2CID 1872341.
  126. ^ Cordell, Dana; Drangert, Jan-Olof; White, Stuart (2009). "The story of phosphorus: Global food security and food for thought". Global Environmental Change. 19 (2): 292–305. doi:10.1016/j.gloenvcha.2008.10.009. S2CID 1450932.
  127. ^ Edixhoven, J. D.; Gupta, J.; Savenije, H. H. G. (December 19, 2014). "Recent revisions of phosphate rock reserves and resources: a critique". Earth System Dynamics. 5 (2): 491–507. Bibcode:2014ESD.....5..491E. doi:10.5194/esd-5-491-2014. ISSN 2190-4987. S2CID 858311.
  128. ^ Amundson, R.; Berhe, A. A.; Hopmans, J. W.; Olson, C.; Sztein, A. E.; Sparks, D. L. (2015). "Soil and human security in the 21st century". Science. 348 (6235): 1261071. doi:10.1126/science.1261071. ISSN 0036-8075. PMID 25954014. S2CID 206562728.
  129. ^ Cheng, Lijing; Trenberth, Kevin E.; Gruber, Nicolas; Abraham, John P.; Fasullo, John T.; Li, Guancheng; Mann, Michael E.; Zhao, Xuanming; Zhu, Jiang (2020). "Improved Estimates of Changes in Upper Ocean Salinity and the Hydrological Cycle". Journal of Climate. 33 (23): 10357–10381. Bibcode:2020JCli...3310357C. doi:10.1175/jcli-d-20-0366.1.
  130. ^ Cheng, Lijing; Abraham, John; Hausfather, Zeke; Trenberth, Kevin E. (January 11, 2019). "How fast are the oceans warming?". Science. 363 (6423): 128–129. Bibcode:2019Sci...363..128C. doi:10.1126/science.aav7619. PMID 30630919. S2CID 57825894.
  131. ^ a b Doney, Scott C.; Busch, D. Shallin; Cooley, Sarah R.; Kroeker, Kristy J. (October 17, 2020). "The Impacts of Ocean Acidification on Marine Ecosystems and Reliant Human Communities". Annual Review of Environment and Resources. 45 (1): 83–112. doi:10.1146/annurev-environ-012320-083019.
    CC BY icon.svg
    Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
  132. ^ Freedman, Andrew (September 29, 2020). "Mixing of the planet's ocean waters is slowing down, speeding up global warming, study finds". The Washington Post. Archived from the original on October 15, 2020. Retrieved October 12, 2020.
  133. ^ Chester, R.; Jickells, Tim (2012). "Chapter 9: Nutrients oxygen organic carbon and the carbon cycle in seawater". Marine geochemistry (3rd ed.). Chichester, West Sussex, UK: Wiley/Blackwell. ISBN 978-1-118-34909-0. OCLC 781078031.
  134. ^ "Chapter 34: The Biosphere: An Introduction to Earth's Diverse Environment". Biology: Concepts & Connections. section 34.7.
  135. ^ a b Cavicchioli R, Ripple WJ, Timmis KN, Azam F, Bakken LR, Baylis M, et al. (September 2019). "Scientists' warning to humanity: microorganisms and climate change". Nature Reviews. Microbiology. 17 (9): 569–586. doi:10.1038/s41579-019-0222-5. PMC 7136171. PMID 31213707.
    CC BY icon.svg
    Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  136. ^ Drogin, B (August 2, 2009). "Mapping an ocean of species". Los Angeles Times. Retrieved August 18, 2009.
  137. ^ Paul, GS (2010). "The Evolution of Dinosaurs and their World". The Princeton Field Guide to Dinosaurs. Princeton: Princeton University Press. p. 19. ISBN 978-0-691-13720-9.
  138. ^ Bortolotti, Dan (2008). Wild blue: a natural history of the world's largest animal. New York: Thomas Dunn Books. ISBN 978-0-312-38387-9. OCLC 213451450.
  139. ^ Bar-On YM, Phillips R, Milo R (June 2018). "The biomass distribution on Earth". Proceedings of the National Academy of Sciences of the United States of America. 115 (25): 6506–6511. Bibcode:2018PNAS..115.6506B. doi:10.1073/pnas.1711842115. PMC 6016768. PMID 29784790.
  140. ^ "Census Of Marine Life". Smithsonian. Retrieved October 29, 2020.
  141. ^ Abercrombie, M., Hickman, C.J. and Johnson, M.L. 1966.A Dictionary of Biology. Penguin Reference Books, London
  142. ^ "Oceanic Institute". Retrieved December 1, 2018.
  143. ^ "Ocean Habitats and Information". January 5, 2017. Retrieved December 1, 2018.
  144. ^ "Facts and figures on marine biodiversity | United Nations Educational, Scientific and Cultural Organization". Retrieved December 1, 2018.
  145. ^ United States Environmental Protection Agency (March 2, 2006). "Marine Ecosystems". Retrieved August 25, 2006.
  146. ^ Zacharias, Mark (March 14, 2014). Marine Policy: An Introduction to Governance and International Law of the Oceans. Routledge. ISBN 9781136212475.
  147. ^ Halpern, Benjamin S.; Walbridge, Shaun; Selkoe, Kimberly A.; Kappel, Carrie V.; Micheli, Fiorenza; D'Agrosa, Caterina; Bruno, John F.; Casey, Kenneth S.; Ebert, Colin; Fox, Helen E.; Fujita, Rod (2008). "A Global Map of Human Impact on Marine Ecosystems". Science. 319 (5865): 948–952. Bibcode:2008Sci...319..948H. doi:10.1126/science.1149345. ISSN 0036-8075. PMID 18276889. S2CID 26206024.
  148. ^ Sauerbier, Charles L.; Meurn, Robert J. (2004). Marine Cargo Operations: a guide to stowage. Cambridge, Md: Cornell Maritime Press. pp. 1–16. ISBN 978-0-87033-550-1.
  149. ^ "Industry Globalization | World Shipping Council". Retrieved May 4, 2021.
  150. ^ a b c The State of World Fisheries and Aquaculture 2020. FAO. 2020. doi:10.4060/ca9229en. hdl:10535/3776. ISBN 978-92-5-132692-3. S2CID 242949831.
  151. ^ "Fisheries: Latest data". GreenFacts. Retrieved April 23, 2013.
  152. ^ a b "What is Ocean Energy". Ocean Energy Systems. 2014. Retrieved May 14, 2021.
  153. ^ Cruz, João (2008). Ocean Wave Energy – Current Status and Future Perspectives. Springer. p. 2. ISBN 978-3-540-74894-6.
  154. ^ "Offshore Wind Power 2010". BTM Consult. 22 November 2010. Archived from the original on 30 June 2011. Retrieved 25 April 2013.
  155. ^ Lamb, Robert (2011). "How offshore drilling works". HowStuffWorks. Retrieved May 6, 2013.
  156. ^ a b "The United Nations Convention on the Law of the Sea (A historical perspective)". United Nations Division for Ocean Affairs and the Law of the Sea. Retrieved May 8, 2013.
  157. ^ Evans, J. P. (2011). Environmental Governance. Hoboken: Taylor & Francis. ISBN 978-0-203-15567-7. OCLC 798531922.
  158. ^ Halpern, B.S.; Frazier, M.; Afflerbach, J.; et al. (2019). "Recent pace of change in human impact on the world's ocean". Scientific Reports. 9 (1): 11609. Bibcode:2019NatSR...911609H. doi:10.1038/s41598-019-47201-9. PMC 6691109. PMID 31406130.
  159. ^ Charles Sheppard, ed. (2019). World seas : an Environmental Evaluation. Vol. III, Ecological Issues and Environmental Impacts (Second ed.). London. ISBN 978-0128052044. OCLC 1052566532.
  160. ^ Duce, Robert, Galloway, J. and Liss, P. (2009). "The Impacts of Atmospheric Deposition to the Ocean on Marine Ecosystems and Climate WMO Bulletin Vol 58 (1)". Retrieved September 22, 2020.
  161. ^ "What is the biggest source of pollution in the ocean?". National Ocean Service (US). Silver Spring, MD: National Oceanic and Atmospheric Administration. Retrieved September 21, 2022.
  162. ^ Weisman, Alan (2007). The World Without Us. St. Martin's Thomas Dunne Books. ISBN 978-0312347291.
  163. ^ "Marine plastic pollution". IUCN. May 25, 2018. Retrieved February 1, 2022.
  164. ^ H, Eskarina; ley (January 26, 2022). "Nanoplastics in snow: The extensive impact of plastic pollution". Open Access Government. Retrieved February 1, 2022.
  165. ^ Jang, Y. C., Lee, J., Hong, S., Choi, H. W., Shim, W. J., & Hong, S. Y. 2015. Estimating the global inflow and stock of plastic marine debris using material flow analysis: a preliminary approach. Journal of the Korean Society for Marine Environment and Energy, 18(4), 263–273.[1]
  166. ^ "Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics". UNEP – UN Environment Programme. October 21, 2021. Retrieved March 21, 2022.
  167. ^ Wright, Pam (June 6, 2017). "UN Ocean Conference: Plastics Dumped In Oceans Could Outweigh Fish by 2050, Secretary-General Says". The Weather Channel. Retrieved May 5, 2018.
  168. ^ Ostle, Clare; Thompson, Richard C.; Broughton, Derek; Gregory, Lance; Wootton, Marianne; Johns, David G. (2019). "The rise in ocean plastics evidenced from a 60-year time series". Nature Communications. 10 (1): 1622. Bibcode:2019NatCo..10.1622O. doi:10.1038/s41467-019-09506-1. ISSN 2041-1723. PMC 6467903. PMID 30992426.
  169. ^ "Research |AMRF/ORV Alguita Research Projects" Archived 13 March 2017 at the Wayback Machine Algalita Marine Research Foundation. Macdonald Design. Retrieved 19 May 2009
  170. ^ UNEP (2005) Marine Litter: An Analytical Overview
  171. ^ Six pack rings hazard to wildlife Archived 13 October 2016 at the Wayback Machine.
  172. ^ Louisiana Fisheries – Fact Sheets.
  173. ^ "'Ghost fishing' killing seabirds". BBC News. June 28, 2007.
  174. ^ Efferth, Thomas; Paul, Norbert W (November 2017). "Threats to human health by great ocean garbage patches". The Lancet Planetary Health. 1 (8): e301–e303. doi:10.1016/s2542-5196(17)30140-7. ISSN 2542-5196. PMID 29628159.
  175. ^ Gibbs, Susan E.; Salgado Kent, Chandra P.; Slat, Boyan; Morales, Damien; Fouda, Leila; Reisser, Julia (April 9, 2019). "Cetacean sightings within the Great Pacific Garbage Patch". Marine Biodiversity. 49 (4): 2021–2027. doi:10.1007/s12526-019-00952-0.
  176. ^ Scales, Helen (March 29, 2007). "Shark Declines Threaten Shellfish Stocks, Study Says". National Geographic News. Retrieved May 1, 2012.
  177. ^ Olsen, Erik; Kaplan, Isaac C.; Ainsworth, Cameron; Fay, Gavin; Gaichas, Sarah; Gamble, Robert; Girardin, Raphael; Eide, Cecilie H.; Ihde, Thomas F.; Morzaria-Luna, Hem Nalini; Johnson, Kelli F.; Savina-Rolland, Marie; Townsend, Howard; Weijerman, Mariska; Fulton, Elizabeth A.; Link, Jason S. (2018). "Ocean Futures Under Ocean Acidification, Marine Protection, and Changing Fishing Pressures Explored Using a Worldwide Suite of Ecosystem Models". Frontiers in Marine Science. 5: 64. doi:10.3389/fmars.2018.00064. ISSN 2296-7745.
  178. ^ Manson, Paul; Nielsen-Pincus, Max; Granek, Elise F.; Swearingen, Thomas C. (February 15, 2021). "Public perceptions of ocean health and marine protection: Drivers of support for Oregon's marine reserves". Ocean & Coastal Management. 201: 105480. doi:10.1016/j.ocecoaman.2020.105480. ISSN 0964-5691. S2CID 230555294.
  179. ^ Deng, Na; Chen, Xu; Xiong, Caiquan (2020). "Design and Construction of Intelligent Decision-Making System for Marine Protection and Law Enforcement". Advances on Broad-Band Wireless Computing, Communication and Applications. Lecture Notes in Networks and Systems. Springer International Publishing. 97: 828–837. doi:10.1007/978-3-030-33506-9_75. ISBN 978-3-030-33505-2. S2CID 208114517.
  180. ^ "Protecting the Marine Environment". March 26, 2014. Retrieved October 25, 2021.
  181. ^ "Quantitative targets for marine protection: a review of the scientific basis and applications" (PDF). Retrieved October 25, 2021.
  182. ^ Farran, Sue. "Is marine protection compatible with the right to economic development in Pacific Island States?".
  183. ^ Cabral, Reniel B.; Bradley, Darcy; Mayorga, Juan; Goodell, Whitney; Friedlander, Alan M.; Sala, Enric; Costello, Christopher; Gaines, Steven D. (November 10, 2020). "A global network of marine protected areas for food". Proceedings of the National Academy of Sciences. 117 (45): 28134–28139. Bibcode:2020PNAS..11728134C. doi:10.1073/pnas.2000174117. ISSN 0027-8424. PMC 7668080. PMID 33106411.
  184. ^ Dinerstein, E.; Vynne, C.; Sala, E.; Joshi, A. R.; Fernando, S.; Lovejoy, T. E.; Mayorga, J.; Olson, D.; Asner, G. P.; Baillie, J. E. M.; Burgess, N. D.; Burkart, K.; Noss, R. F.; Zhang, Y. P.; Baccini, A.; Birch, T.; Hahn, N.; Joppa, L. N.; Wikramanayake, E. (2019). "A Global Deal For Nature: Guiding principles, milestones, and targets". Science Advances. 5 (4): eaaw2869. Bibcode:2019SciA....5.2869D. doi:10.1126/sciadv.aaw2869. PMC 6474764. PMID 31016243.
  185. ^ "Improving ocean protection with the first marine protected areas guide". Institut de Recherche pour le Développement. Retrieved October 19, 2021.
  186. ^ Grorud-Colvert, Kirsten; Sullivan-Stack, Jenna; Roberts, Callum; Constant, Vanessa; Horta e Costa, Barbara; Pike, Elizabeth P.; Kingston, Naomi; Laffoley, Dan; Sala, Enric; Claudet, Joachim; Friedlander, Alan M.; Gill, David A.; Lester, Sarah E.; Day, Jon C.; Gonçalves, Emanuel J.; Ahmadia, Gabby N.; Rand, Matt; Villagomez, Angelo; Ban, Natalie C.; Gurney, Georgina G.; Spalding, Ana K.; Bennett, Nathan J.; Briggs, Johnny; Morgan, Lance E.; Moffitt, Russell; Deguignet, Marine; Pikitch, Ellen K.; Darling, Emily S.; Jessen, Sabine; Hameed, Sarah O.; Di Carlo, Giuseppe; Guidetti, Paolo; Harris, Jean M.; Torre, Jorge; Kizilkaya, Zafer; Agardy, Tundi; Cury, Philippe; Shah, Nirmal J.; Sack, Karen; Cao, Ling; Fernandez, Miriam; Lubchenco, Jane (2021). "The MPA Guide: A framework to achieve global goals for the ocean" (PDF). Science. 373 (6560): eabf0861. doi:10.1126/science.abf0861. PMID 34516798. S2CID 237473020.
  187. ^ Hendrix, Amanda R.; Hurford, Terry A.; Barge, Laura M.; Bland, Michael T.; Bowman, Jeff S.; Brinckerhoff, William; Buratti, Bonnie J.; Cable, Morgan L.; Castillo-Rogez, Julie; Collins, Geoffrey C.; et al. (2019). "The NASA Roadmap to Ocean Worlds". Astrobiology. 19 (1): 1–27. Bibcode:2019AsBio..19....1H. doi:10.1089/ast.2018.1955. PMC 6338575. PMID 30346215.
  188. ^ Dyches, Preston; Chou, Felcia (April 7, 2015). "The Solar System and Beyond is Awash in Water". NASA. Retrieved April 8, 2015.
  189. ^ NASA (June 18, 2020). "Are planets with oceans common in the galaxy? It's likely, NASA scientists find". EurekAlert!. Retrieved June 20, 2020.
  190. ^ Shekhtman, Lonnie; et al. (June 18, 2020). "Are Planets with Oceans Common in the Galaxy? It's Likely, NASA Scientists Find". NASA. Retrieved June 20, 2020.
  191. ^ "A Freaky Fluid inside Jupiter?". NASA. Retrieved December 8, 2021.
  192. ^ "NASA System Exploration Jupiter". NASA. Retrieved December 8, 2021.
  193. ^ "Oceans of diamond possible on Uranus and Neptune". Astronomy Now. Retrieved December 8, 2021.
  194. ^ Magazine, Smithsonian. "It May Rain Diamonds Inside Neptune and Uranus". Smithsonian Magazine. Retrieved December 8, 2021.