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86-406: AABW forms near the surface in coastal polynyas along the coastline of Antarctica, where high rates of sea ice formation during winter leads to the densification of the surface waters through brine rejection . Since the water mass forms near the surface, it is responsible for the exchange of large quantities of heat and gases with the atmosphere. AABW has a high oxygen content relative to the rest of

172-492: A World Heritage Site for their geological value, four of them are considered of "Outstanding Universal Value" based on their cultural and natural criteria: Þingvellir , Iceland; Landscape of the Pico Island Vineyard Culture , Portugal; Gough and Inaccessible Islands , United Kingdom; and Brazilian Atlantic Islands: Fernando de Noronha and Atol das Rocas Reserves, Brazil. Continental shelves in

258-506: A Navy Sonic Depth Finder to draw a continuous map across the bed of the Atlantic. This involved little guesswork because the idea of sonar is straightforward with pulses being sent from the vessel, which bounce off the ocean floor, then return to the vessel. The deep ocean floor is thought to be fairly flat with occasional deeps, abyssal plains , trenches , seamounts , basins , plateaus , canyons , and some guyots . Various shelves along

344-721: A branch of the Gulf Stream which flows northward from the Grand Banks ; and the Subpolar Front , an extension of the North Atlantic Current, a wide, vaguely defined region separating the subtropical gyre from the subpolar gyre. This system of currents transports warm water into the North Atlantic, without which temperatures in the North Atlantic and Europe would plunge dramatically. North of

430-526: A large amount of brine rejection into the surface waters; this salty water then sinks. It is an open question as to whether the polynyas of the Arctic can produce enough dense water to form a major portion of the dense water required to drive the thermohaline circulation . Mid-sea polynyas are formed when specific atmospheric conditions occur over preconditioned oceanographic areas. Such atmospheric conditions should favor ice drift in opposite directions to open

516-510: A major role in bottom water formation and deep-sea circulation, which deposits oxygen to the deep sea and is a major carbon sink . Without these connections, the deep sea will become drastically changed with the potential for collapse in entire deep-sea communities. Some studies indicate that WSBW formation in the Weddell Sea is dominantly driven by wind-driven sea ice changes, however, and that increased sea ice formation overcompensates for

602-455: A natural ice hole and was adopted in the 19th century by polar explorers to describe navigable portions of the sea. There are two main types of polynyas: coastal polynyas, which can be found year-round near the Antarctic and Arctic coasts and are mainly created by strong winds pushing the ice away from the coast, and mid-sea or open-ocean polynyas, which may be found more sporadically in

688-415: A polynya. The presence of open water in an otherwise ice-covered area can result in a localized marine algal bloom , also referred to as a polynya bloom. While algal communities are often found under sea ice , as evidenced by ice algae , the rate of phytoplankton growth is substantially higher in the open water of a polynya. The primary drivers of polynya blooms are sunlight and nutrients. Specifically,

774-435: A result of containing more phytoplankton than the surrounding water. Therefore, due to the role of primary producers as the foundation of the marine food web , polynyas are a critical food source for a variety of organisms such as fish, birds, and marine mammals. Listed below are several examples of the importance of polynyas to polar communities. Polynyas have also supported human populations throughout history. For example,

860-530: A single season, amounting to about 2,000 km of sea ice. Surface water is enriched in salt from sea ice formation and cooled due to being exposed to a cold atmosphere during winter, which increases the density of this water mass. Due to its increased density, it forms overflows down the Antarctic continental slope and continues north along the bottom. It is the densest water in the open ocean, and underlies other bottom and intermediate waters throughout most of

946-416: A weak Intertropical Convergence Zone , South Atlantic tropical cyclones are rare. The Atlantic Ocean is underlain mostly by dense mafic oceanic crust made up of basalt and gabbro and overlain by fine clay, silt and siliceous ooze on the abyssal plain. The continental margins and continental shelf mark lower density, but greater thickness felsic continental rock that is often much older than that of

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1032-621: Is a complex of four water masses, two that form by deep convection in the open ocean – classical and upper Labrador sea water – and two that form from the inflow of dense water across the Greenland-Iceland-Scotland sill – Denmark Strait and Iceland-Scotland overflow water. Along its path across Earth the composition of the NADW is affected by other water masses, especially Antarctic bottom water and Mediterranean overflow water. The NADW

1118-467: Is fed by a flow of warm shallow water into the northern North Atlantic which is responsible for the anomalous warm climate in Europe. Changes in the formation of NADW have been linked to global climate changes in the past. Since human-made substances were introduced into the environment, the path of the NADW can be traced throughout its course by measuring tritium and radiocarbon from nuclear weapon tests in

1204-498: Is found off the eastern coast of Canada. Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar energy, range from below −2 °C (28 °F) to over 30 °C (86 °F). Maximum temperatures occur north of the equator, and minimum values are found in the polar regions. In the middle latitudes, the area of maximum temperature variations, values may vary by 7–8 °C (13–14 °F). From October to June

1290-575: Is interrupted by larger transform faults at two places: the Romanche Trench near the Equator and the Gibbs fracture zone at 53°N . The MAR is a barrier for bottom water, but at these two transform faults deep water currents can pass from one side to the other. The MAR rises 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and its rift valley is the divergent boundary between

1376-854: Is intersected by two perpendicular ridges: the Azores–Gibraltar Transform Fault , the boundary between the Nubian and Eurasian plates , intersects the MAR at the Azores triple junction , on either side of the Azores microplate, near the 40°N . A much vaguer, nameless boundary, between the North American and South American plates, intersects the MAR near or just north of the Fifteen-Twenty fracture zone , approximately at 16°N . In

1462-729: Is now northern and central Brazil. The formation of the Central American Isthmus closed the Central American Seaway at the end of the Pliocene 2.8 Ma ago. The formation of the isthmus resulted in the migration and extinction of many land-living animals, known as the Great American Interchange , but the closure of the seaway resulted in a "Great American Schism" as it affected ocean currents, salinity, and temperatures in both

1548-794: Is now the Carpathian region, that were similar to the Sargasso Sea. It is possible that the population in the Sargasso Sea migrated to the Atlantic as the Tethys closed at the end of the Miocene around 17 Ma. The origin of the Sargasso fauna and flora remained enigmatic for centuries. The fossils found in the Carpathians in the mid-20th century often called the "quasi-Sargasso assemblage", finally showed that this assemblage originated in

1634-985: The Iliad and the Odyssey , this all-encompassing ocean was instead known as Oceanus , the gigantic river that encircled the world; in contrast to the enclosed seas well known to the Greeks: the Mediterranean and the Black Sea. In contrast, the term "Atlantic" originally referred specifically to the Atlas Mountains in Morocco and the sea off the Strait of Gibraltar and the West African coast. The term " Aethiopian Ocean ", derived from Ancient Ethiopia ,

1720-797: The Age of Discovery , it was known for separating the New World of the Americas ( North America and South America ) from the Old World of Afro-Eurasia ( Africa , Asia , and Europe ). Through its separation of Afro-Eurasia from the Americas, the Atlantic Ocean has played a central role in the development of human society, globalization, and the histories of many nations. While the Norse were

1806-784: The Agulhas Passage and over the southern margins of the Agulhas Plateau and then into the Mozambique Basin . Climate change and the subsequent melting of the Southern ice sheet have slowed the formation of AABW, and this slowdown is likely to continue. A complete shutdown of AABW formation is possible as soon as 2050. This shutdown would have dramatic effects on ocean circulation and global weather patterns. Increased intrusion of warm Circumpolar Deep Water coupled with enhanced ice shelf basal melting can impact

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1892-564: The Carpathian Basin from where it migrated over Sicily to the central Atlantic where it evolved into modern species of the Sargasso Sea. The location of the spawning ground for European eels remained unknown for decades . In the early 19th century it was discovered that the southern Sargasso Sea is the spawning ground for both the European and American eel and that the former migrate more than 5,000 km (3,100 mi) and

1978-610: The Columbian exchange while occasionally hosting naval battles. Such naval battles, as well as growing trade from regional American powers like the United States and Brazil , both increased in degree during the early 20th century, and while no major military conflicts have taken place in the Atlantic recently, the ocean remains a core component of trade around the world. The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to

2064-530: The Equator . The oldest known mentions of an "Atlantic" sea come from Stesichorus around mid-sixth century BC (Sch. A. R. 1. 211): Atlantikôi pelágei (Ancient Greek: Ἀτλαντικῷ πελάγει , ' the Atlantic sea ' , etym . ' Sea of Atlas ' ) and in The Histories of Herodotus around 450 BC (Hdt. 1.202.4): Atlantis thalassa (Ancient Greek: Ἀτλαντὶς θάλασσα , ' Sea of Atlas ' or '

2150-474: The Icelandic Low produces frequent storms. Icebergs are common from early February to the end of July across the shipping lanes near the Grand Banks of Newfoundland . The ice season is longer in the polar regions, but there is little shipping in those areas. Hurricanes are a hazard in the western parts of the North Atlantic during the summer and autumn. Due to a consistently strong wind shear and

2236-684: The North American and Eurasian plates in the North Atlantic and the South American and African plates in the South Atlantic. The MAR produces basaltic volcanoes in Eyjafjallajökull , Iceland, and pillow lava on the ocean floor. The depth of water at the apex of the ridge is less than 2,700 m (1,500 fathoms ; 8,900  ft ) in most places, while the bottom of the ridge is three times as deep. The MAR

2322-616: The North Atlantic Drift is thought to have at least some influence on climate. For example, the Gulf Stream helps moderate winter temperatures along the coastline of southeastern North America, keeping it warmer in winter along the coast than inland areas. The Gulf Stream also keeps extreme temperatures from occurring on the Florida Peninsula. In the higher latitudes, the North Atlantic Drift, warms

2408-514: The North Atlantic oscillation , occurs. On average, the Atlantic is the saltiest major ocean; surface water salinity in the open ocean ranges from 33 to 37 parts per thousand (3.3–3.7%) by mass and varies with latitude and season. Evaporation, precipitation, river inflow and sea ice melting influence surface salinity values. Although the lowest salinity values are just north of the equator (because of heavy tropical rainfall), in general,

2494-502: The North Water Polynya , the largest and most biologically productive Arctic polynya, serves as a critical source of food in an otherwise barren region, enabling the existence of high-latitude human communities in the region for thousands of years. It may have served as a stepping stone for the original settlers of Greenland as they traversed through what is now northern Canada 4500 years ago. There are also indications that

2580-676: The Romanche Fracture Zone into the eastern Atlantic. In the Guiana Basin, west of 40°W, the sloping topography and the strong, eastward flowing deep western boundary current might prevent the Antarctic bottom water from flowing west: thus it has to turn north at the eastern slope of the Ceará Rise . At 44°W, north of the Ceará Rise, Antarctic bottom water flows west in the interior of the basin. A large fraction of

2666-555: The Scotia Sea , and other tributary water bodies. Including these marginal seas the coast line of the Atlantic measures 111,866 km (69,510 mi) compared to 135,663 km (84,297 mi) for the Pacific. Including its marginal seas, the Atlantic covers an area of 106,460,000 km (41,100,000 sq mi) or 23.5% of the global ocean and has a volume of 310,410,900 km (74,471,500 cu mi) or 23.3% of

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2752-466: The Southern Ocean . It plays a major role in the global overturning circulation. Coastal polynyas (latent heat polynyas) are a source of AABW as brine rejection during the formation of sea ice at these polynyas increases the salinity of the seawater, which then sinks down to the ocean bottom as AABW. Antarctic polynyas form when ice masses diverge from the coast and move away in the direction of

2838-582: The Weddell Sea area. While the freshening of the AABW has corrected itself over the past few years with a decrease in ice melt, the potential for more ice melt in the future still poses a threat. With the potential increase in ice melt at extreme-enough levels, it can have a serious impact on the ability for deep sea water to be formed. While this would create a slowdown referenced above, it may also create additional warming. Increased stratification coming from

2924-421: The ice shelf . An important factor enabling the formation of Antarctic bottom water is the cold surface wind blowing off the Antarctic continent. The surface winds advect sea ice away from the coast, creating polynyas which opens up the water surface to a cold atmosphere during winter, which further helps form more sea ice. Antarctic coastal polynyas form as much as 10% of the overall Southern Ocean sea ice during

3010-638: The meridional overturning circulation (MOC), the northward heat transport of which is threatened by anthropogenic climate change. Large variations in the subpolar gyre on a decade-century scale, associated with the North Atlantic oscillation , are especially pronounced in Labrador Sea Water , the upper layers of the MOC. The South Atlantic is dominated by the anti-cyclonic southern subtropical gyre. The South Atlantic Central Water originates in this gyre, while Antarctic Intermediate Water originates in

3096-458: The thermocline of the subtropical gyre. The Sargasso Sea in the western North Atlantic can be defined as the area where two species of Sargassum ( S. fluitans and natans ) float, an area 4,000 km (2,500 mi) wide and encircled by the Gulf Stream , North Atlantic Drift , and North Equatorial Current . This population of seaweed probably originated from Tertiary ancestors on

3182-578: The 1870s, the Challenger expedition discovered parts of what is now known as the Mid-Atlantic Ridge, or: An elevated ridge rising to an average height of about 1,900 fathoms [3,500 m; 11,400 ft] below the surface traverses the basins of the North and South Atlantic in a meridianal direction from Cape Farewell, probably its far south at least as Gough Island, following roughly

3268-618: The 1953 definition it extends south to Antarctica, while in later maps it is bounded at the 60° parallel by the Southern Ocean. The Atlantic has irregular coasts indented by numerous bays, gulfs and seas. These include the Baltic Sea , Black Sea , Caribbean Sea , Davis Strait , Denmark Strait , part of the Drake Passage , Gulf of Mexico , Labrador Sea , Mediterranean Sea , North Sea , Norwegian Sea , almost all of

3354-485: The 1960s and CFCs . The clockwise warm-water North Atlantic Gyre occupies the northern Atlantic, and the counter-clockwise warm-water South Atlantic Gyre appears in the southern Atlantic. In the North Atlantic, surface circulation is dominated by three inter-connected currents: the Gulf Stream which flows north-east from the North American coast at Cape Hatteras ; the North Atlantic Current ,

3440-836: The Antarctic bottom water enters the eastern Atlantic through the Vema Fracture Zone . In the Indian Ocean , the Crozet–Kerguelen Gap allows Antarctic bottom water to move toward the equator. This northward movement amounts to 2.5  Sv . It takes the Antarctic Bottom Water 23 years to reach the Crozet-Kerguelen Gap. South of Africa, Antarctic bottom water flows northwards through the Agulhas Basin and then east through

3526-537: The Atlantic are wide off Newfoundland, southernmost South America, and northeastern Europe. In the western Atlantic carbonate platforms dominate large areas, for example, the Blake Plateau and Bermuda Rise . The Atlantic is surrounded by passive margins except at a few locations where active margins form deep trenches : the Puerto Rico Trench (8,376 m or 27,480 ft maximum depth) in

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3612-625: The Atlantic include the Challenger expedition and the German Meteor expedition ; as of 2001 , Columbia University 's Lamont–Doherty Earth Observatory and the United States Navy Hydrographic Office conduct research on the ocean. The MAR divides the Atlantic longitudinally into two halves, in each of which a series of basins are delimited by secondary, transverse ridges. The MAR reaches above 2,000 m (6,600 ft) along most of its length, but

3698-403: The Atlantic north of the equator. The coldest zones are in high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents influence the climate by transporting warm and cold waters to other regions. The winds that are cooled or warmed when blowing over these currents influence adjacent land areas. The Gulf Stream and its northern extension towards Europe,

3784-557: The Atlantic sea ' ) where the name refers to "the sea beyond the pillars of Heracles " which is said to be part of the sea that surrounds all land. In these uses, the name refers to Atlas , the Titan in Greek mythology , who supported the heavens and who later appeared as a frontispiece in medieval maps and also lent his name to modern atlases . On the other hand, to early Greek sailors and in ancient Greek mythological literature such as

3870-409: The Bahamas, while coarse river outwash sands and silt are common in shallow shelf areas like the Georges Bank . Coarse sand, boulders, and rocks were transported into some areas, such as off the coast of Nova Scotia or the Gulf of Maine during the Pleistocene ice ages. The break-up of Pangaea began in the central Atlantic, between North America and Northwest Africa, where rift basins opened during

3956-404: The European shores of the former Tethys Ocean and has, if so, maintained itself by vegetative growth , floating in the ocean for millions of years. Other species endemic to the Sargasso Sea include the sargassum fish , a predator with algae-like appendages which hovers motionless among the Sargassum . Fossils of similar fishes have been found in fossil bays of the former Tethys Ocean, in what

4042-419: The Holocene (last 10,000 years) is not in a steady-state condition; that is, bottom water production sites shift along the Antarctic margin over decade-to-century timescales as conditions for the existence of polynyas change. For example, the calving of the Mertz Glacier , which occurred on 12–13 February 2010, dramatically changed the environment for producing bottom water, reducing export by up to 23% in

4128-405: The Late Triassic and Early Jurassic. This period also saw the first stages of the uplift of the Atlas Mountains. The exact timing is controversial with estimates ranging from 200 to 170 Ma. The opening of the Atlantic Ocean coincided with the initial break-up of the supercontinent Pangaea , both of which were initiated by the eruption of the Central Atlantic Magmatic Province (CAMP), one of

4214-468: The North Atlantic Gyre, the cyclonic North Atlantic Subpolar Gyre plays a key role in climate variability. It is governed by ocean currents from marginal seas and regional topography, rather than being steered by wind, both in the deep ocean and at sea level. The subpolar gyre forms an important part of the global thermohaline circulation . Its eastern portion includes eddying branches of the North Atlantic Current which transport warm, saline waters from

4300-404: The North Water Polynya has aided Thule , Inuit , Norse , and western explorers throughout history. Today, the North Water Polynya enables the existence of Greenland's northernmost towns, such as Qaanaaq , Qeqertat , Savissivik and Siorapaluk . When submarines of the U.S. Navy made expeditions to the North Pole in the 1950s and 1960s, there was significant concern about surfacing through

4386-457: The South Atlantic at 31°18′S 39°24′W  /  31.3°S 39.4°W  / -31.3; -39.4 , is an important conduit for Antarctic Bottom Water and Weddell Sea Bottom Water migrating north. Upon reaching the equator , about one-third of the northward flowing Antarctic bottom water enters the Guiana Basin , mainly through the southern half of the Equatorial Channel at 35°W. The other part recirculates and some of it flows through

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4472-437: The South Atlantic, and the "Atmospheric Bridge", which evaporates subtropical Atlantic waters and exports it to the Pacific. The Atlantic Ocean consists of four major, upper water masses with distinct temperature and salinity. The Atlantic subarctic upper water in the northernmost North Atlantic is the source for subarctic intermediate water and North Atlantic intermediate water. North Atlantic central water can be divided into

4558-412: The atmosphere over the oceans, keeping the British Isles and northwestern Europe mild and cloudy, and not severely cold in winter, like other locations at the same high latitude. The cold water currents contribute to heavy fog off the coast of eastern Canada (the Grand Banks of Newfoundland area) and Africa's northwestern coast. In general, winds transport moisture and air over land areas. Every winter,

4644-425: The east, and the Americas to the west. As one component of the interconnected World Ocean , it is connected in the north to the Arctic Ocean , to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south. Other definitions describe the Atlantic as extending southward to Antarctica . The Atlantic Ocean is divided in two parts, the northern and southern Atlantic, by

4730-431: The east, the boundaries of the ocean proper are Europe: the Strait of Gibraltar (where it connects with the Mediterranean Sea  – one of its marginal seas  – and, in turn, the Black Sea , both of which also touch upon Asia) and Africa. In the southeast, the Atlantic merges into the Indian Ocean. The 20° East meridian , running south from Cape Agulhas to Antarctica defines its border. In

4816-544: The eastern and western North Atlantic central water since the western part is strongly affected by the Gulf Stream and therefore the upper layer is closer to underlying fresher subpolar intermediate water. The eastern water is saltier because of its proximity to Mediterranean water. North Atlantic central water flows into South Atlantic central water at 15°N . There are five intermediate waters: four low-salinity waters formed at subpolar latitudes and one high-salinity formed through evaporation. Arctic intermediate water flows from

4902-430: The first known humans to cross the Atlantic, it was the expedition of Christopher Columbus in 1492 that proved to be the most consequential. Columbus' expedition ushered in an age of exploration and colonization of the Americas by European powers , most notably Portugal , Spain , France , and the United Kingdom . From the 16th to 19th centuries, the Atlantic Ocean was the center of both an eponymous slave trade and

4988-498: The formation of dense shelf waters. For surface water to become deep water, it must be very cold and saline. Much of the deep-water formation comes from brine rejection, where the water deposited is extremely saline and cold, making it extremely dense. The increased ice melt that occurred starting in the early 2000s has created a period of fresher water between 2011-2015 within the bottom water. This has been distinctly prevalent in Antarctic bottom waters near West Antarctica , primarily in

5074-521: The fresher and warmer waters will reduce bottom and deep-water circulation and increase warm water flows around Antarctica. The sustained warmer surface waters would only increase the level of ice melt, stratification, and the slowdown of the AABW circulation and formation. Additionally, without the presence of those colder waters producing brine rejection which deposits to the AABW, there may eventually be no formation of bottom water around Antarctica anymore. This would impact more than Antarctica, as AABW plays

5160-410: The ice pack. Polar cyclones are a typical atmospheric trigger for the occurrence of mid-sea polynyas as the cyclonic winds push the ice in opposite directions away from the cyclone center. Also, cold fronts, where two opposite flows in direction are found, are ideal for creating a mid-sea polynya. Antarctic bottom water (AABW) is the dense water with high salinity that exists in the abyssal layer of

5246-460: The intruding warm CDW water masses from gaining access to the base of ice shelves, hence acting to protect ice shelves from enhanced basal melting due to oceanic warming. In areas like the Amundsen Sea, where coastal polynya activity has diminished to the point where dense water formation is hindered, the neighboring ice shelves have started to retreat and may be on the brink of collapse. Evidence indicates that Antarctic bottom water production through

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5332-526: The lack of sea ice allows light, a necessary component for photosynthesis , to penetrate deeper into the water and enable elevated phytoplankton growth compared to the surrounding ice-covered waters. Furthermore, polynya formation is typically associated with upwelling , a process that transports nutrient-rich water from the ocean bottom towards the surface. This influx of nutrients coupled with increased light levels often results in polynya blooms. In general, polynyas tend to be more biologically productive as

5418-454: The latter 2,000 km (1,200 mi). Ocean currents such as the Gulf Stream transport eel larvae from the Sargasso Sea to foraging areas in North America, Europe, and northern Africa. Recent but disputed research suggests that eels possibly use Earth's magnetic field to navigate through the ocean both as larvae and as adults. The climate is influenced by the temperatures of the surface waters and water currents as well as winds. Because of

5504-474: The limits of the oceans and seas in 1953, but some of these definitions have been revised since then and some are not recognized by various authorities, institutions, and countries, for example the CIA World Factbook . Correspondingly, the extent and number of oceans and seas vary. The Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Strait , Greenland Sea , Norwegian Sea and Barents Sea . To

5590-429: The lowest values are in the high latitudes and along coasts where large rivers enter. Maximum salinity values occur at about 25° north and south , in subtropical regions with low rainfall and high evaporation. The high surface salinity in the Atlantic, on which the Atlantic thermohaline circulation is dependent, is maintained by two processes: the Agulhas Leakage/Rings , which brings salty Indian Ocean waters into

5676-454: The margins of the continents constitute about 11% of the bottom topography with few deep channels cut across the continental rise. The mean depth between 60°N and 60°S is 3,730 m (12,240 ft), or close to the average for the global ocean, with a modal depth between 4,000 and 5,000 m (13,000 and 16,000 ft). In the South Atlantic the Walvis Ridge and Rio Grande Rise form barriers to ocean currents. The Laurentian Abyss

5762-407: The maximum depth, the Milwaukee Deep in the Puerto Rico Trench , is 8,376 m (27,480 ft). Top large seas: The bathymetry of the Atlantic is dominated by a submarine mountain range called the Mid-Atlantic Ridge (MAR). It runs from 87°N or 300 km (190 mi) south of the North Pole to the subantarctic Bouvet Island at 54°S . Expeditions to explore the bathymertry of

5848-456: The melting of ice sheets, rendering the effects of melting Antarctic glaciers on WSBW minimal. Polynya A polynya ( / p ə ˈ l ɪ n j ə / ) is an area of open water surrounded by sea ice . It is now used as a geographical term for an area of unfrozen seawater within otherwise contiguous pack ice or fast ice . It is a loanword from the Russian полынья ( Russian pronunciation: [pəɫɨˈnʲja] ), which refers to

5934-711: The middle of ice pack in certain locations, especially around Antarctica. These locations are generally preconditioned by certain oceanic dynamics. One of the most famous mid-sea polynyas is the Weddell Polynya , also known as the Maud Rise Polynya, which occurs in the Lazarev Sea over the Maud Rise seamount. It was first spotted in September 1973 and persisted through multiple winters (1974–1976), and recently recurred in September 2017. Coastal polynyas are formed through two main processes: Latent heat polynyas are regions of high ice production and therefore are possible sites of dense water production in both polar regions . The high ice production rates within these polynyas leads to

6020-510: The most extensive and voluminous large igneous provinces in Earth's history associated with the Triassic–Jurassic extinction event , one of Earth's major extinction events . Theoliitic dikes , sills , and lava flows from the CAMP eruption at 200 Ma have been found in West Africa, eastern North America, and northern South America. The extent of the volcanism has been estimated to 4.5 × 10  km (1.7 × 10  sq mi) of which 2.5 × 10  km (9.7 × 10  sq mi) covered what

6106-502: The north to become the source for North Atlantic deep water, south of the Greenland-Scotland sill. These two intermediate waters have different salinity in the western and eastern basins. The wide range of salinities in the North Atlantic is caused by the asymmetry of the northern subtropical gyre and a large number of contributions from a wide range of sources: Labrador Sea, Norwegian-Greenland Sea, Mediterranean, and South Atlantic Intermediate Water. The North Atlantic deep water (NADW)

6192-425: The ocean's great capacity to store and release heat, maritime climates are more moderate and have less extreme seasonal variations than inland climates. Precipitation can be approximated from coastal weather data and air temperature from water temperatures. The oceans are the major source of atmospheric moisture that is obtained through evaporation. Climatic zones vary with latitude; the warmest zones stretch across

6278-520: The oceans' deep waters, but this depletes over time. This water sinks at four distinct regions around the margins of the continent and forms the AABW; this process leads to ventilation of the deep ocean, or abyssal ventilation . Antarctic bottom water is created is formed in the Weddell and Ross Seas , off the Adélie Coast and by Cape Darnley from surface water cooling in polynyas and below

6364-565: The outlines of the coasts of the Old and the New Worlds. The remainder of the ridge was discovered in the 1920s by the German Meteor expedition using echo-sounding equipment. The exploration of the MAR in the 1950s led to the general acceptance of seafloor spreading and plate tectonics . Most of the MAR runs under water but where it reaches the surfaces it has produced volcanic islands. While nine of these have collectively been nominated

6450-651: The pond" or "on the other side of the pond" or "across the pond", rather than to discuss the ocean itself. The term dates to 1640, first appearing in print in a pamphlet released during the reign of Charles I , and reproduced in 1869 in Nehemiah Wallington 's Historical Notices of Events Occurring Chiefly in The Reign of Charles I , where "great Pond" is used in reference to the Atlantic Ocean by Francis Windebank , Charles I's Secretary of State . The International Hydrographic Organization (IHO) defined

6536-519: The region of Adélie Land . Evidence from sediment cores, containing layers of cross-bedded sediments indicating phases of stronger bottom currents, collected on the Mac. Robertson shelf and Adélie Land suggests that they have switched "on" and "off" again as important bottom water production sites over the last several thousand years. The Vema Channel, a deep trough in the Rio Grande Rise of

6622-438: The seafloor. The oldest oceanic crust in the Atlantic is up to 145 million years and is situated off the west coast of Africa and the east coast of North America, or on either side of the South Atlantic. In many places, the continental shelf and continental slope are covered in thick sedimentary layers. For instance, on the North American side of the ocean, large carbonate deposits formed in warm shallow waters such as Florida and

6708-423: The southern hemisphere. The Weddell Sea Bottom Water is the densest component of the Antarctic bottom water. A major source water for the formation of AABW is the warm offshore watermass known as the circumpolar deep water (CDW; salinity > 35 g/kg and potential temperature > 0C). These warm watermasses are cooled by coastal polynyas to form the denser AABW. Coastal polynyas that form AABW help prevent

6794-551: The subtropics to the northeastern Atlantic. There this water is cooled during winter and forms return currents that merge along the eastern continental slope of Greenland where they form an intense (40–50  Sv ) current which flows around the continental margins of the Labrador Sea . A third of this water becomes part of the deep portion of the North Atlantic Deep Water (NADW). The NADW, in turn, feeds

6880-421: The surface is usually covered with sea ice in the Labrador Sea , Denmark Strait , and Baltic Sea. The Coriolis effect circulates North Atlantic water in a clockwise direction, whereas South Atlantic water circulates counter-clockwise. The south tides in the Atlantic Ocean are semi-diurnal; that is, two high tides occur every 24 lunar hours. In latitudes above 40° North some east–west oscillation, known as

6966-705: The thick pack ice of the Arctic Ocean. In 1962, both the USS Skate and USS Seadragon surfaced within the same large polynya near the North Pole for the first polar rendezvous of the U.S. Atlantic Fleet and the U.S. Pacific Fleet . Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceanic divisions , with an area of about 85,133,000 km (32,870,000 sq mi). It covers approximately 17% of Earth's surface and about 24% of its water surface area. During

7052-480: The total volume of the Earth's oceans. Excluding its marginal seas, the Atlantic covers 81,760,000 km (31,570,000 sq mi) and has a volume of 305,811,900 km (73,368,200 cu mi). The North Atlantic covers 41,490,000 km (16,020,000 sq mi) (11.5%) and the South Atlantic 40,270,000 km (15,550,000 sq mi) (11.1%). The average depth is 3,646 m (11,962 ft) and

7138-636: The upper layers of the circumpolar region, near the Drake Passage and the Falkland Islands. Both these currents receive some contribution from the Indian Ocean. On the African east coast, the small cyclonic Angola Gyre lies embedded in the large subtropical gyre. The southern subtropical gyre is partly masked by a wind-induced Ekman layer . The residence time of the gyre is 4.4–8.5 years. North Atlantic Deep Water flows southward below

7224-424: The western Atlantic and South Sandwich Trench (8,264 m or 27,113 ft) in the South Atlantic. There are numerous submarine canyons off northeastern North America, western Europe, and northwestern Africa. Some of these canyons extend along the continental rises and farther into the abyssal plains as deep-sea channels. In 1922, a historic moment in cartography and oceanography occurred. The USS Stewart used

7310-634: The wind, creating an exposed area of sea water which subsequently freezes over, with brine rejection, to form another mass of ice. Some polynyas, such as the North Water Polynya between Canada and Greenland , occur seasonally at the same time and place each year. Because animals can adapt their life strategies to this regularity, these types of polynyas are of special ecological research significance. In winter, marine mammals such as walruses , narwhals , and belugas that do not migrate south remain there. Polar bears are known to be able to swim as far as 65 kilometres (35 nautical miles) across open waters of

7396-494: Was applied to the southern Atlantic as late as the mid-19th century. During the Age of Discovery , the Atlantic was also known to English cartographers as the Great Western Ocean . The pond is a term often used by British and American speakers in reference to the northern Atlantic Ocean, as a form of meiosis , or ironic understatement. It is used mostly when referring to events or circumstances "on this side of

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