1.
North Atlantic Drift (album)
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North Atlantic Drift is the sixth album by Ocean Colour Scene. Bush and British Prime Minister Tony Blair, respectively, the first track, I Just Need Myself was played by Virgin Radio and reached #13 in the charts, though the other two singles did less well but still charted inside the top 40. The folky Second Hand Car was released as a single in Germany, the album was released to a largely mixed-to-negative reception. It was the last album released with the line up after Damon Minchella left the band in late 2003
North Atlantic Drift (album)
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North Atlantic Drift
2.
Western boundary current
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Boundary currents are ocean currents with dynamics determined by the presence of a coastline, and fall into two distinct categories, western boundary currents and eastern boundary currents. Eastern boundary currents are relatively shallow, broad and slow-flowing and they are found on the eastern side of oceanic basins. Coastal upwelling often brings nutrient-rich water into eastern boundary current regions, western boundary currents are warm, deep, narrow, and fast flowing currents that form on the west side of ocean basins due to western intensification. They carry warm water from the tropics poleward, examples include the Gulf Stream, the Agulhas Current, and the Kuroshio. Western intensification is the intensification of the arm of an oceanic current. The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes and this wind pattern applies a stress to the subtropical ocean surface with negative curl in the northern hemisphere and a positive curl in the southern hemisphere. The resulting Sverdrup transport is equatorward in both cases, western intensification also occurs in the polar gyres, where the sign of the wind stress curl and the direction of the resulting currents are reversed. It is because of western intensification that the currents on the boundary of a basin are stronger than those on the eastern boundary. Western intensification was first explained by the American oceanographer Henry Stommel, the wind is blowing towards the west at y =0 and towards the east at y = b. Such currents are observed to be faster, deeper, narrower and warmer than their eastern counterparts. The streamlines exhibit a behavior in all directions, with the height contours demonstrating a nearly parallel relation to the streamlines. The physics of western intensification can be understood through a mechanism that helps maintain the balance along an ocean gyre. He assumed a geostrophic flow, while neglecting any frictional or viscosity effects. Sverdrup introduced a potential vorticity argument to connect the net, interior flow of the oceans to the wind stress. This is accomplished via a decrease in planetary vorticity, a phenomenon attainable through an equator-wardly directed, the opposite is applicable when Ekman divergence is induced, leading to Ekman absorption and a subsequent, water column stretching and poleward return flow, a characteristic of sub-polar gyres. This return flow, as shown by Stommel, occurs in a meridional current, to balance the vorticity source induced by the wind stress forcing, Stommel introduced a linear frictional term in the Sverdrup equation, functioning as the vorticity sink. Walter Munk further implemented Stommels theory of western intensification by using a more realistic frictional term, Ekman Transport Ocean Gyres Sverdrup Balance Thurman, Harold V. Trujillo, Alan P. On the wind-driven ocean circulation, J. Meteorol, Ocean Currents, A Derivative of the Encyclopedia of Ocean Sciences
Western boundary current
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The main ocean currents involved with the North Pacific Gyre
3.
Gulf Stream
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The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America. At about 40°0′N 30°0′W, it splits in two, with the stream, the North Atlantic Drift, crossing to Northern Europe and the southern stream. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and it is part of the North Atlantic Gyre. Its presence has led to the development of strong cyclones of all types, the Gulf Stream is also a significant potential source of renewable power generation. The Gulf Stream may be slowing down as a result of climate change, the Gulf Stream is typically 100 kilometres wide and 800 metres to 1,200 metres deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second. European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de León and its existence was also known to Peter Martyr dAnghiera. Benjamin Franklin became interested in the North Atlantic Ocean circulation patterns, Franklin asked Timothy Folger, his cousin twice removed, a Nantucket Island whaling captain, for an answer. Franklin worked with Folger and other experienced ship captains, learning enough to chart the Gulf Stream and he offered this information to Anthony Todd, secretary of the British Post Office, but it was ignored by British sea captains. Franklins Gulf Stream chart was published in 1770 in England, where it was mostly ignored, subsequent versions were printed in France in 1778 and the U. S. in 1786. The Gulf Stream proper is a current, driven largely by wind stress. The North Atlantic Drift, in contrast, is largely thermohaline circulation–driven, in 1958 the oceanographer Henry Stommel noted that very little water from the Gulf of Mexico is actually in the Stream. By carrying warm water northeast across the Atlantic, it makes Western, a river of sea water, called the Atlantic North Equatorial Current, flows westward off the coast of Central Africa. When this current interacts with the northeastern coast of South America, one passes into the Caribbean Sea, while a second, the Antilles Current, flows north and east of the West Indies. These two branches north of the Straits of Florida. The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes and this wind pattern applies a stress to the subtropical ocean surface with negative curl across the north Atlantic Ocean. The resulting Sverdrup transport is equatorward, the conservation of potential vorticity also causes bends along the Gulf Stream, which occasionally break off due to a shift in the Gulf Streams position, forming separate warm and cold eddies. This overall process, known as western intensification, causes currents on the boundary of an ocean basin, such as the Gulf Stream
Gulf Stream
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Surface temperature in the western North Atlantic. North America is black and dark blue (cold), the Gulf Stream red (warm). Source:
NASA
Gulf Stream
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Benjamin Franklin 's map of the Gulf Stream
Gulf Stream
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Evolution of the Gulf Stream to the west of Ireland continuing as the
North Atlantic Current
Gulf Stream
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Hurricane Alex formed and moved along the axis of the Gulf Stream in 2004.
4.
Grand Banks of Newfoundland
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The Grand Banks of Newfoundland are a group of underwater plateaus south-east of Newfoundland on the North American continental shelf. These areas are shallow, ranging from 50 to 300 feet in depth. The cold Labrador Current mixes with the waters of the Gulf Stream here. The mixing of waters and the shape of the ocean bottom lifts nutrients to the surface. These conditions helped to create one of the richest fishing grounds in the world, fish species include Atlantic cod, swordfish, haddock and capelin, shellfish include scallop and lobster. The area also supports colonies of seabirds such as northern gannets, shearwaters and sea ducks and various sea mammals such as seals, dolphins. In addition to the effects on nutrients, the mixing of the cold and it is also noted for its proximity to the sinking of the RMS Titanic and thus the launching point of Titanic shipwreck expeditions. The Grand Banks were extensively glaciated during the last glacial maximum, by approximately 13,000 years ago, the majority of the ice had melted, leaving the Grand Banks exposed as several islands extending for hundreds of kilometers. It is believed that sea levels submerged these around 8,000 years ago. Within a few years of Cabots voyage the existence of fishing grounds on the Grand Banks became generally known in Europe, ships from France and Portugal were first to fish there, followed by those from Spain while ships from England were scarce in the early years. This soon changed especially after Bernard Drakes devastating raid in 1585 which virtually wiped out the Spanish and these fish stocks thus became important for the early economies of eastern Canada and New England. Canadas EEZ currently occupies the majority of the Grand Banks except for the lucrative nose, the 1783 Treaty of Paris gave the United States shared rights to fish in these waters, but that section of the Treaty is no longer in force. Once this aspect of UNCLOS is ratified, Canada will presumably control these remaining parts of Grand Banks which are outside of its EEZ jurisdiction. Semi-fictional depictions of working on the Grand Banks can be found in Rudyard Kiplings novel Captains Courageous. The Grand Banks are also portrayed in the 1990 film The Hunt for Red October
Grand Banks of Newfoundland
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Historic map including the Grand Banks.
Grand Banks of Newfoundland
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Map showing the Grand Banks
Grand Banks of Newfoundland
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By country
Grand Banks of Newfoundland
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Fisheries
5.
Azores
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Its main industries are agriculture, dairy farming, livestock, fishing, and tourism, which is becoming the major service activity in the region. In addition, the government of the Azores employs a large percentage of the population directly or indirectly in the service, the main settlement of the Azores is Ponta Delgada. There are nine major Azorean islands and a cluster, in three main groups. These are Flores and Corvo, to the west, Graciosa, Terceira, São Jorge, Pico, and Faial in the centre, and São Miguel, Santa Maria, and they extend for more than 600 km and lie in a northwest-southeast direction. All the islands have volcanic origins, although some, such as Santa Maria, have had no recorded activity since the islands were settled, mount Pico, on the island of Pico, is the highest point in Portugal, at 2,351 m. The Azores are actually some of the tallest mountains on the planet, measured from their base at the bottom of the ocean to their peaks, which thrust high above the surface of the Atlantic. The climate of the Azores is very mild for such a location, being influenced by its distance to continents. Due to the influence, temperatures remain mild year-round. Daytime temperatures normally fluctuate between 16 °C and 25 °C depending on season, temperatures above 30 °C or below 3 °C are unknown in the major population centres. It is also generally wet and cloudy, the culture, dialect, cuisine, and traditions of the Azorean islands vary considerably, because these once-uninhabited and remote islands were settled sporadically over a span of two centuries. However, these kinds of structures have always used in the Azores to store cereals. Detailed examination and dating to authenticate the validity of these speculations is lacking and it is unclear whether these structures are natural or man-made and whether they predate the 15th-century Portuguese colonization of the Azores. Solid confirmation of a human presence in the archipelago has not yet been published. The islands were known in the century and parts of them appear in the Atlas Catalan. In 1427, a captain sailing for Henry the Navigator, possibly Gonçalo Velho, rediscovered the Azores, but this is not certain. In Thomas Ashes 1813 work, A History of the Azores, the author identified a Fleming, Joshua Vander Berg of Bruges and he stated that the Portuguese explored the area and claimed it for Portugal. Other stories note the discovery of the first islands by sailors in the service of Henry the Navigator, although there are few documents to support the claims. Although it is said that the archipelago received its name from the goshawk
Azores
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Mount Pico and the green landscape, emblematic of the archipelago of the Azores
Azores
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1584 map of the Azores.
Azores
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Angra do Heroísmo, the oldest continuously-settled town in the archipelago of the Azores and UNESCO World Heritage Site
Azores
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This article is about the archipelago. For the area of high pressure, see
Azores High.
6.
Flemish Cap
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The Flemish Cap is an area of shallow waters in the north Atlantic Ocean centered roughly at 47° north, 45° west or about 350 miles east of St. Johns, Newfoundland and Labrador. The shallow water is caused by an underwater plateau covering an extended area of 12,000 square miles. Depths at the cap range from approximately 400 feet to 2,300 feet, the Flemish Cap is located within an area of transition between the cold waters of the Labrador Current and warmer waters influenced by the Gulf Stream. The mixing of the warmer and colder waters over the plateau produces the characteristic clockwise circulation current over the cap, the waters of the Flemish Cap are deeper and warmer than the Grand Banks of Newfoundland. The 58, 000-square-kilometre area may have served as an important refuge for marine species during the last ice age, the waters of the Flemish Cap are noted as excellent fishing waters. Halibut, swordfish, shrimp, scallop, yellowtail and other species may be found in abundance there. The Flemish Cap lies outside Canadas 200 nautical mile Exclusive Economic Zone established in 1977, overfishing has become a serious issue in recent years. Cod and American plaice are particularly endangered here and the numbers of redfish have shown a significant decline, in recent years, Canada had made an effort to prevent overfishing in the region by use of provisions of the Coastal Fisheries Protection Act and the United Nations Fish Stocks Agreement. The origin of the Flemish Caps name is unclear and it arguably refers to Flemish fishermen venturing out this far west in the nineteenth century. This area was filmed by Wolfgang Petersen in his 2000 film The Perfect Storm as the final fishing grounds of the Andrea Gail. Overfishing, The Grand Banks and the Flemish Cap Government response to the committee on fisheries
Flemish Cap
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By country
Flemish Cap
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Map showing the Flemish Cap at far right
Flemish Cap
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Fisheries
7.
Mid-Atlantic Ridge
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In the North Atlantic, it separates the Eurasian and North American Plates, whereas in the South Atlantic it separates the African and South American Plates. The ridge extends from a junction with the Gakkel Ridge northeast of Greenland southward to the Bouvet Triple Junction in the South Atlantic, although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level. The section of the ridge that includes the island of Iceland is also known as the Reykjanes Ridge, the ridge has an average spreading rate of about 2.5 cm per year. A ridge under the Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1850, the ridge was discovered during the expedition of HMS Challenger in 1872. A team of scientists on board, led by Charles Wyville Thomson, the existence of such a ridge was confirmed by sonar in 1925 and was found to extend around the Cape of Good Hope into the Indian Ocean by the German Meteor expedition. Ewing, Heezen and Tharp discovered that the ridge is part of a 40, the ridge is central to the breakup of the hypothetical supercontinent of Pangaea that began some 180 million years ago. The Mid-Atlantic Ridge includes a deep valley that runs along the axis of the ridge along nearly its entire length. This rift marks the boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava. This trench, however, is not regarded as the boundary between the North and South American Plates, nor the Eurasian and African Plates and this bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere. This divergent boundary first formed in the Triassic period, when a series of three-armed grabens coalesced on the supercontinent Pangaea to form the ridge, usually, only two arms of any given three-armed graben become part of a divergent plate boundary. The failed arms are called aulacogens, and the aulacogens of the Mid-Atlantic Ridge eventually became many of the river valleys seen along the Americas. The Fundy Basin on the Atlantic coast of North America between New Brunswick and Nova Scotia in Canada is evidence of the ancestral Mid-Atlantic Ridge, atlantis Massif Central Atlantic Magmatic Province Fifteen-Twenty Fracture Zone Evans, Rachel. Plumbing Depths to Reach New Heights, Marie Tharp Explains Marine Geological Maps, the Library of Congress Information Bulletin. MAR-ECO, a Census of Marine Life project on life along the Mid-Atlantic Ridge
Mid-Atlantic Ridge
–
A
fissure of the ridge in the Þingvellir National Park, Iceland
Mid-Atlantic Ridge
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A map of the Mid-Atlantic Ridge
Mid-Atlantic Ridge
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A rock outcrop of the ridge at Thingvellir in Iceland
8.
Labrador Current
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It is a continuation of the West Greenland Current and the Baffin Island Current. It meets the warm Gulf Stream at the Grand Banks southeast of Newfoundland, the combination of these two currents produces heavy fogs and has also created one of the richest fishing grounds in the world. In spring and early summer, this current transports icebergs from the glaciers of Greenland southwards into the shipping lanes. The waters of the Labrador Current have an effect on the Canadian Atlantic provinces. The transport of the Labrador Current is believed to contain a large barotropic component, early estimates indicated that the current may be 30% stronger than geostrophic calculations indicated as a result of a significant barotropic flow component. Greenberg and Petrie calculated a total transport of 7.6 sverdrup, the geostrophic transport was calculated to be just 4.1 Sv. With a 30% increase the transport is only 5.3 Sv so, speeds for the Labrador Current are about 0. 3–0.5 m/s along the shelf edge. Current speeds of 0. 3–0.5 m/s were found by Reynaud et al. for the Labrador Current. Including the barotropic component, they estimate a value of 3 Sv for the continental shelf branch of the Labrador Current and 16 Sv transport for the branch of the Labrador Current. Within the Flemish Pass, Petrie and Isenor report that the width of the Labrador Current is reduced to 50 km with a speed of 0.25 m/s which they believe is actually 0.30 m/s. The Labrador Current has a tendency to go farther south and/or east than normal. This can produce hazardous shipping conditions as it can carry icebergs into an area of the Atlantic where they are not usually found, the current has been known to transport icebergs as far south as Bermuda and as far east as the Azores. After the sinking of the RMS Titanic in 1912, the International Ice Patrol was set up to track icebergs, surface Currents in the Atlantic Ocean
Labrador Current
–
Photo of
eddies in the Labrador Current
Labrador Current
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Map of Labrador Current
9.
Continental Europe
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Continental Europe, also referred to as mainland Europe, or, by Europeans, simply the Continent, is the continuous continent of Europe, excluding surrounding islands. This historical core of Carolingian Europe was consciously invoked in the 1950s as the historical basis for the prospective European integration. In both Great Britain and Ireland, the Continent is widely and generally used to refer to the mainland of Europe, an apocryphal British newspaper headline supposedly once read, Fog in Channel, Continent Cut Off. It has also claimed that this was a regular weather forecast in Britain in the 1930s. In addition, the word Europe itself is regularly used to mean Europe excluding the islands of Great Britain, Iceland. The term mainland Europe is also sometimes used, derivatively, the adjective continental refers to the social practices or fashion of continental Europe. Examples include breakfast, topless sunbathing and, historically, long-range driving often known as Grand Touring. Differences include electrical plugs, time zones for the most part, the use of traffic, and for the United Kingdom, currency. Britain is physically connected to continental Europe through the undersea Channel Tunnel and this route is popular with refugees and migrants seeking to enter the UK. Especially in Germanic studies, continental refers to the European continent excluding the Scandinavian peninsula, Britain, Ireland, and Iceland. The reason for this is that although the Scandinavian peninsula is attached to continental Europe, kontinenten is a vernacular Swedish expression that refers to the area excluding Sweden, Norway, and Finland but including Denmark and the rest of continental Europe. In Norway, similarly, one speaks about Kontinentet as an entity, usually referring to Germany, France, Italy, Spain, Portugal, the Benelux countries. Today, the Scandinavian peninsula is accessible by train and road with several bridge/tunnel structures connecting the Danish peninsula of Jutland to Scania in Sweden. The Continent may sometimes refer to the part of Italy, the continental part of Spain, the continental part of France. The term is used from the perspective of the residents of each country to describe the continental portion of their country or the continent as a whole. Continental philosophy Geopolitical divisions of Europe Geographical midpoint of Europe Mainland Western Europe Hajnal line
Continental Europe
–
Map of the Scandiae islands by
Nicolaus Germanus for a 1467 publication of Cosmographia Claudii Ptolomaei Alexandrini.
Continental Europe
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Continental Europe (green area); the boundaries of the continent are somewhat
disputed.
10.
Canary Current
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The Canary Current is a wind-driven surface current that is part of the North Atlantic Gyre. This eastern boundary current branches south from the North Atlantic Current and flows southwest about as far as Senegal where it turns west, the current is named after the Canary Islands. The archipelago partially blocks the flow of the Canary Current and this wide and slow moving current is thought to have been exploited in the early Phoenician navigation and settlement along the coast of western Morocco. A prominent feature of Eastern Boundary Currents is the presence of upwelling, ekman drift causes offshore transport of surface waters, which are then replaced with deep water from below. Deep waters are cold and nutrient-rich and have a key role in stimulating primary productivity, upwelling has led to the enhancement of coastal fisheries in western Morocco. Major upwelling occurs between 23 and 25 degrees northern latitude, upwelling occurs year-round at Cap Blanc and northward. South of Cap Blanc, upwelling is limited to winter and spring due to the migration of the Azores high during summer. Minas et al. showed that at the latitude of Cap Blanc, SACW, to the south of Cap Blanc, is richer in nutrients than NACW. A poleward subsurface counter-current is responsible for bringing SACW to the Cap Blanc region resulting in maximal primary production, primary production to the north is limited by nutrient availability in NACW. Primary production to the south of Cap Blanc is limited by the occurrence of upwelling events, Huntsman and Barber hypothesized that high productivity results from alternating upwelling events and relatively calm periods. Upwelling is necessary to bring the nutrients to the surface but if the event is sustained for a period of time. Calm periods allow for stratification to develop, which means that phytoplankton can grow, in other words, there is a miniature spring bloom during each calm period. Upwelling and primary production follow the onset of a wind within a few days. Zooplankton, such as copepods, take longer to respond to the abundance of food available because they have life cycles of weeks rather than days, zooplankton in the Canary Current reach their peak density in autumn when upwelling intensity decreases. The decrease in upwelling allows the zooplankton to stay over the shelf where their food supply exists, due to the rapid response of phytoplankton to upwelled nutrients, zooplankton are seldom food-limited. Four types of fish comprise 75% of total catch in the Cap Blanc region, S. pilchards dominate in the cooler northern waters while S. aurita are prevalent in warmer southern waters. Next most abundant were Jack mackerel and Redfish, Ansa-Emmin found that in 1974, the total fish landings reached 2.68 million tons. Nearly 1 million tons were Clupeidae with.67 million tons being sardines, phytoplankton over the shelf area face two fates, They sink to the bottom or are consumed by zooplankton
Canary Current
–
EUMETSAT (European Meteorological satellite) image from Northwest Africa, showing the lack of clouds on the upwelling waters of the Canary Current
11.
Africa
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Africa is the worlds second-largest and second-most-populous continent. At about 30.3 million km² including adjacent islands, it covers 6% of Earths total surface area and 20.4 % of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the human population. The continent includes Madagascar and various archipelagos and it contains 54 fully recognized sovereign states, nine territories and two de facto independent states with limited or no recognition. Africas population is the youngest amongst all the continents, the age in 2012 was 19.7. Algeria is Africas largest country by area, and Nigeria by population, afarensis, Homo erectus, H. habilis and H. ergaster – with the earliest Homo sapiens found in Ethiopia being dated to circa 200,000 years ago. Africa straddles the equator and encompasses numerous climate areas, it is the continent to stretch from the northern temperate to southern temperate zones. Africa hosts a diversity of ethnicities, cultures and languages. In the late 19th century European countries colonized most of Africa, Africa also varies greatly with regard to environments, economics, historical ties and government systems. However, most present states in Africa originate from a process of decolonization in the 20th century, afri was a Latin name used to refer to the inhabitants of Africa, which in its widest sense referred to all lands south of the Mediterranean. This name seems to have referred to a native Libyan tribe. The name is connected with Hebrew or Phoenician ʿafar dust. The same word may be found in the name of the Banu Ifran from Algeria and Tripolitania, under Roman rule, Carthage became the capital of the province of Africa Proconsularis, which also included the coastal part of modern Libya. The Latin suffix -ica can sometimes be used to denote a land, the later Muslim kingdom of Ifriqiya, modern-day Tunisia, also preserved a form of the name. According to the Romans, Africa lay to the west of Egypt, while Asia was used to refer to Anatolia, as Europeans came to understand the real extent of the continent, the idea of Africa expanded with their knowledge. 25,4, whose descendants, he claimed, had invaded Libya, isidore of Seville in Etymologiae XIV.5.2. Suggests Africa comes from the Latin aprica, meaning sunny, massey, in 1881, stated that Africa is derived from the Egyptian af-rui-ka, meaning to turn toward the opening of the Ka. The Ka is the double of every person and the opening of the Ka refers to a womb or birthplace
Africa
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Map of Africa
Africa
–
Africa
Africa
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Lucy, an
Australopithecus afarensis skeleton discovered on November 24, 1974, in the
Awash Valley of
Ethiopia 's
Afar Depression
Africa
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Colossal statues of
Ramesses II at
Abu Simbel, Egypt, date from around 1400 BC.
12.
Northwestern Europe
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Northwestern Europe, or Northwest Europe, is the loosely defined northwestern region of Europe. The phrase is defined geographically and ethnographically. Geographically, Northwestern Europe usually consists of Ireland, the United Kingdom, Belgium, the Netherlands, northern Germany, Denmark, Norway, Sweden, Luxembourg, northern France, southern Germany, and Switzerland are also often considered part of the grouping. Austria is also defined as Northwestern Europe, though less frequently. Southern France is not regarded as northwestern, and it is geographically and culturally considered part of the Mediterranean region or Southern Europe. Due to its geographically eastern position and unique status as a Finnic language country, the term is helpful when discussing issues of climate or biology. The region also has a history of Protestantism that differentiates it from its Mediterranean / Southern European / Latin and Eastern European / Slavic neighbors. In military history, especially in Commonwealth countries, the battle honour North-West Europe has been used to refer to the two campaigns in that approximate area during World War II. Two separate battle honours were awarded to regiments who took part in these campaigns, the North-West Europe Campaign of 1940, during the Battle of France, was restricted to Belgium and the French Channel ports. In the First campaign the French Army was responsible for the rest of the Western Front from Luxembourg to Switzerland, as were the American 12th Army and 6th Army Groups during the second campaign. A period of warfare existed from 1 November 1944 to 8 February 1945 during which time the First Canadian Army manned positions in the Nijmegen Salient
Northwestern Europe
–
Dark green – minimum extent of northwest Europe Green – maximum extent of northwest Europe
13.
Thermohaline circulation
–
Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
Thermohaline circulation
–
Global map of average Sea Surface Density
Thermohaline circulation
–
A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents.
Thermohaline circulation
–
Benjamin Franklin 's map of the
Gulf Stream
14.
North America
–
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery. Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa, Asia and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, alternatively, usage sometimes includes Greenland and Mexico, as well as offshore islands
North America
–
Map of North America, from 1621.
North America
–
North America
North America
–
The
El Castillo pyramid, at
Chichén Itzá, Mexico.
North America
–
Benjamin West 's
The Death of General Wolfe (1771) depicting the
Battle of the Plains of Abraham.
15.
Atlantic
–
The Atlantic Ocean is the second largest of the worlds oceans with a total area of about 106,460,000 square kilometres. It covers approximately 20 percent of the Earths surface and about 29 percent of its surface area. It separates the Old World from the New World, the Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. The Equatorial Counter Current subdivides it into the North Atlantic Ocean, in contrast, the term Atlantic originally referred specifically to the Atlas Mountains in Morocco and the sea off the Strait of Gibraltar and the North African coast. The Greek word thalassa has been reused by scientists for the huge Panthalassa ocean that surrounded the supercontinent Pangaea hundreds of years ago. The term Aethiopian Ocean, derived from Ancient Ethiopia, was applied to the Southern Atlantic as late as the mid-19th century, many Irish or British people refer to the United States and Canada as across the pond, and vice versa. The Black Atlantic refers to the role of ocean in shaping black peoples history. Irish migration to the US is meant when the term The Green Atlantic is used, the term Red Atlantic has been used in reference to the Marxian concept of an Atlantic working class, as well as to the Atlantic experience of indigenous Americans. Correspondingly, the extent and number of oceans and seas varies, 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, to the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltar 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 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. Including these marginal seas the coast line of the Atlantic measures 111,866 km compared to 135,663 km for the Pacific. Including its marginal seas, the Atlantic covers an area of 106,460,000 km2 or 23. 5% of the ocean and has a volume of 310,410,900 km3 or 23. 3%. Excluding its marginal seas, the Atlantic covers 81,760,000 km2 and has a volume of 305,811,900 km3, the North Atlantic covers 41,490,000 km2 and the South Atlantic 40,270,000 km2. The average depth is 3,646 m and the maximum depth, the bathymetry of the Atlantic is dominated by a submarine mountain range called the Mid-Atlantic Ridge. It runs from 87°N or 300 km south of the North Pole to the subantarctic Bouvet Island at 42°S, 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 2000 m along most of its length, 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
Atlantic
–
The Atlantic Ocean as seen from the western coast of
Portugal
Atlantic
–
The Atlantic Ocean, not including
Arctic and
Antarctic regions
Atlantic
–
The Atlantic Ocean as seen from
Atlantic City, New Jersey.
Atlantic
–
Myrtle Beach, South Carolina view of the Atlantic Ocean.
16.
Arctic Ocean
–
The Arctic Ocean is the smallest and shallowest of the worlds five major oceans. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean, located mostly in the Arctic north polar region in the middle of the Northern Hemisphere, the Arctic Ocean is almost completely surrounded by Eurasia and North America. It is partly covered by sea ice throughout the year and almost completely in winter, the summer shrinking of the ice has been quoted at 50%. The US National Snow and Ice Data Center uses satellite data to provide a record of Arctic sea ice cover. The Arctic may become ice free for the first time in human history within a few years or by 2040, for much of European history, the north polar regions remained largely unexplored and their geography conjectural. He was probably describing loose sea ice known today as growlers or bergy bits, his Thule was probably Norway, early cartographers were unsure whether to draw the region around the North Pole as land or water. The makers of navigational charts, more conservative than some of the more fanciful cartographers, tended to leave the region blank and this lack of knowledge of what lay north of the shifting barrier of ice gave rise to a number of conjectures. In England and other European nations, the myth of an Open Polar Sea was persistent, john Barrow, longtime Second Secretary of the British Admiralty, promoted exploration of the region from 1818 to 1845 in search of this. In the United States in the 1850s and 1860s, the explorers Elisha Kane, even quite late in the century, the eminent authority Matthew Fontaine Maury included a description of the Open Polar Sea in his textbook The Physical Geography of the Sea. Nevertheless, as all the explorers who travelled closer and closer to the reported, the polar ice cap is quite thick. Fridtjof Nansen was the first to make a crossing of the Arctic Ocean. The first surface crossing of the ocean was led by Wally Herbert in 1969, in a dog sled expedition from Alaska to Svalbard, with air support. The first nautical transit of the pole was made in 1958 by the submarine USS Nautilus. Since 1937, Soviet and Russian manned drifting ice stations have extensively monitored the Arctic Ocean, scientific settlements were established on the drift ice and carried thousands of kilometres by ice floes. In World War II, the European region of the Arctic Ocean was heavily contested, the Arctic Ocean occupies a roughly circular basin and covers an area of about 14,056,000 km2, almost the size of Antarctica. The coastline is 45,390 km long and it is surrounded by the land masses of Eurasia, North America, Greenland, and by several islands. It is connected to the Pacific Ocean by the Bering Strait and to the Atlantic Ocean through the Greenland Sea, countries bordering the Arctic Ocean are, Russia, Norway, Iceland, Greenland, Canada and the United States. There are several ports and harbours around the Arctic Ocean In Alaska, in Canada, ships may anchor at Churchill in Manitoba, Nanisivik in Nunavut, Tuktoyaktuk or Inuvik in the Northwest territories
Arctic Ocean
–
A
bathymetric /
topographic of the Arctic Ocean and the surrounding lands.
Arctic Ocean
–
Emanuel Bowen 's 1780s map of the Arctic features a "Northern Ocean".
Arctic Ocean
–
Sea cover in the Arctic Ocean, showing the median, 2005 and 2007 coverage
Arctic Ocean
–
Three
polar bears approach
USS Honolulu near the
North Pole.
17.
North Atlantic Oscillation
–
The North Atlantic Oscillation is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through fluctuations in the strength of the Icelandic low and the Azores high, it controls the strength and direction of westerly winds and it is part of the Arctic oscillation, and varies over time with no particular periodicity. The NAO was discovered through several studies in the late 19th, unlike the El Niño-Southern Oscillation phenomenon in the Pacific Ocean, the NAO is a largely atmospheric mode. It is one of the most important manifestations of climate fluctuations in the North Atlantic, the North Atlantic Oscillation is closely related to the Arctic oscillation or Northern Annular Mode, but should not be confused with the Atlantic Multidecadal Oscillation. The NAO has multiple possible definitions, all are attempting to capture the same pattern of variation, by choosing stations in the eye of the two stable pressure areas, the Azores high and the Icelandic low. A more complex definition, only possible with more modern records generated by numerical weather prediction, is based on the principal empirical orthogonal function of surface pressure. This definition has a degree of correlation with the station-based definition. This then leads onto a debate as to whether the NAO is distinct from the AO/NAM, and if not, westerly winds blowing across the Atlantic bring moist air into Europe. In years when westerlies are strong, summers are cool, winters are mild, if westerlies are suppressed, the temperature is more extreme in summer and winter leading to heat waves, deep freezes and reduced rainfall. A permanent low-pressure system over Iceland and a permanent high-pressure system over the Azores control the direction, the relative strengths and positions of these systems vary from year to year and this variation is known as the NAO. A large difference in the pressure at the two leads to increased westerlies and, consequently, cool summers and mild and wet winters in Central Europe. In contrast, if the index is low, westerlies are suppressed, northern European areas suffer cold dry winters and this brings increased storm activity and rainfall to southern Europe and North Africa. Research now suggests that the NAO may be more predictable than previously assumed, although having a less direct influence than for Western Europe, the NAO is also believed to affect the weather over much of eastern North America. In combination with the El Niño, this effect can produce significantly warmer winters over the northeastern United States, under a positive NAO index, regional reduction in atmospheric pressure results in a regional rise in sea level due to the inverse barometer effect. As paleotempestological research has shown, few major hurricanes struck the Gulf coast during 3000–1400 BC, though not the critical factor, the NAO+ peak in the early 1990s may have contributed to the collapse of the Newfoundland cod fishery. On the East Coast of the United States an NAO+ causes warmer temperatures and increased rainfall and this prevents nutrient-rich upwelling which has reduced productivity. Georges Bank and the Gulf of Maine are affected by this reduced cod catch, the strength of the NAO is also a determinant in the population fluctuations of the intensively studied Soay sheep. Strangely enough, Jonas and Joern found a signal between NAO and grasshopper species composition in the tall grass prairies of the midwestern United States
North Atlantic Oscillation
–
For the rock band, see
North Atlantic Oscillation (band).
18.
Ocean gyre
–
A gyre in oceanography is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect, planetary vorticity along with horizontal and vertical friction, determine the circulation patterns from the wind curl. The term gyre can be used to refer to any type of vortex in the air or the sea, even one that is man-made, atlantic Equatorial Current System Pacific Equatorial Current System Indian Monsoon Gyres The center of a subtropical gyre is a high pressure zone. Circulation around the high pressure is clockwise in the hemisphere and counterclockwise in the southern hemisphere. The high pressure in the center is due to the winds on the northern side of the gyre. These cause frictional surface currents towards the latitude at the center of the gyre and this build-up of water in the center creates flow towards the equator in the upper 1,000 to 2,000 m of the ocean, through rather complex dynamics. This flow is returned towards the pole in a western boundary current. Subpolar gyres form at high latitudes, circulation of surface wind and ocean water is counterclockwise in the Northern Hemisphere, around a low-pressure area, such as the persistent Aleutian Low and the Icelandic Low. Surface currents generally move outward from the center of the system and this drives the Ekman transport, which creates an upwelling of nutrient-rich water from the lower depths. Subpolar circulation in the southern hemisphere is dominated by the Antarctic Circumpolar Current, there are minor gyres in the Weddell Sea and the Ross Sea, the Weddell Gyre and Ross Gyre, which circulate in a clockwise direction. Recently stronger winds, especially the trade winds in the Pacific ocean have provided a mechanism for vertical heat distribution. The effect are changes in the currents, increasing the subtropical overturning. Depending on natural variability, during La Niña years around 30% more heat from the upper layer is transported into the deeper ocean. Several studies in recent years, found an increase in OHC of the deep and upper ocean regions. Because the Coriolis effect is strongest near the poles, water flowing eastward at high latitudes turns sooner and is short circuiting the gyre, at the equator the Coriolis effect is nonexistent and the water flows westward until it encounters a blocking continent. Westward boundary currents are faster and deeper than eastern boundary currents. Ocean gyres are known to collect pollutants
Ocean gyre
–
The five major ocean gyres
19.
Physical oceanography
–
Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters. Physical oceanography is one of several sub-domains into which oceanography is divided, others include biological, chemical and geological oceanography. Physical oceanography may be subdivided into descriptive and dynamical physical oceanography, descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precise as possible. Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and these are part of the large field of Geophysical Fluid Dynamics that is shared together with meteorology. The fundamental role of the oceans in shaping Earth is acknowledged by ecologists, geologists, meteorologists, climatologists, an Earth without oceans would truly be unrecognizable. Roughly 97% of the water is in its oceans. The tremendous heat capacity of the oceans moderates the planets climate, the oceans influence extends even to the composition of volcanic rocks through seafloor metamorphism, as well as to that of volcanic gases and magmas created at subduction zones. Though this apparent discrepancy is great, for land and sea, the respective extremes such as mountains and trenches are rare. Because the vast majority of the oceans volume is deep water. The same percentage falls in a salinity range between 34–35 ppt, there is still quite a bit of variation, however. Surface temperatures can range from below freezing near the poles to 35 °C in restricted tropical seas, in terms of temperature, the oceans layers are highly latitude-dependent, the thermocline is pronounced in the tropics, but nonexistent in polar waters. The halocline usually lies near the surface, where evaporation raises salinity in the tropics and these variations of salinity and temperature with depth change the density of the seawater, creating the pycnocline. Energy for the ocean circulation comes from solar radiation and gravitational energy from the sun, perhaps three quarters of this heat is carried in the atmosphere, the rest is carried in the ocean. The atmosphere is heated from below, which leads to convection, by contrast the ocean is heated from above, which tends to suppress convection. Instead ocean deep water is formed in regions where cold salty waters sink in fairly restricted areas. This is the beginning of the thermohaline circulation, oceanic currents are largely driven by the surface wind stress, hence the large-scale atmospheric circulation is important to understanding the ocean circulation. The Hadley circulation leads to Easterly winds in the tropics and Westerlies in mid-latitudes and this leads to slow equatorward flow throughout most of a subtropical ocean basin. The return flow occurs in an intense, narrow, poleward western boundary current, like the atmosphere, the ocean is far wider than it is deep, and hence horizontal motion is in general much faster than vertical motion
Physical oceanography
–
Perspective view of the sea floor of the Atlantic Ocean and the Caribbean Sea. The purple sea floor at the center of the view is the
Puerto Rico Trench.
Physical oceanography
–
World ocean
bathymetry.
Physical oceanography
–
Hurricane Isabel east of the Bahamas on 15 September 2003
Physical oceanography
–
The Bay of Fundy is a
bay located on the
Atlantic coast of
North America, on the northeast end of the
Gulf of Maine between the
provinces of
New Brunswick and
Nova Scotia.
20.
Ocean current
–
Depth contours, shoreline configurations, and interactions with other currents influence a currents direction and strength. Therefore ocean currents are primarily horizontal water movements, Ocean currents flow for great distances, and together, create the global conveyor belt which plays a dominant role in determining the climate of many of the Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel, for example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any region at the same latitude. Another example is Lima, Peru where the climate is cooler than the tropical latitudes in which the area is located, in these wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of ocean currents move somewhat with the seasons. Deep ocean basins generally have a surface current, in that the eastern equatorward-flowing branch is broad. These western boundary currents are a consequence of the rotation of the Earth, Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is known as the oceans conveyor belt. These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection, where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of robots called Argo. The South Equatorial Currents of the Atlantic and Pacific straddle the equator, though the Coriolis effect is weak near the equator, water moving in the currents on either side of the equator is deflected slightly poleward and replaced by deeper water. Thus, equatorial upwelling occurs in these westward flowing equatorial surface currents, upwelling is an important process because this water from within and below the pycnocline is often rich in nutrients and greatly benefits the growth of marine organisms. By contrast, generally poor conditions for growth prevail in most of the tropical ocean because strong layering isolates deep. Ocean currents are measured in sverdrup, where 1 sv is equivalent to a flow rate of 1,000,000 m3 per second. Surface currents are found on the surface of an ocean, and are driven by large scale wind currents and they are directly affected by the wind—the Coriolis effect plays a role in their behaviors. Horizontal and vertical currents also exist below the pycnocline in the deeper waters. The movement of water due to differences in density as a function of water temperature, ripple marks in sediments, scour lines, and the erosion of rocky outcrops on deep-ocean floors are evidence that relatively strong, localized bottom currents exist
Ocean current
–
Major ocean surface currents (Source:
NOAA)
Ocean current
–
The ocean currents.
Ocean current
–
The
bathymetry of the
Kerguelen Plateau in the
Southern Ocean governs the course of the new current part of the global network of ocean currents (Source:
CSIRO)
Ocean current
–
Coupling data collected by NASA/JPL by several different satellite-borne sensors, researchers have been able to "break through" the ocean's surface to detect "Meddies" -- super-salty warm-water eddies that originate in the Mediterranean Sea and then sink more than a half-mile underwater in the Atlantic Ocean. The Meddies are shown in red in this scientific figure.
21.
East Greenland Current
–
The East Greenland Current is a cold, low salinity current that extends from Fram Strait to Cape Farewell. The current is located off the eastern coast of Greenland along the Greenland continental margin, the current cuts through the Nordic Seas and through the Denmark Strait. The EGC is composed of a mixture of three distinct water masses, the water masses are Polar Water, Atlantic Water, and Deep Water. The top 150 meters of the EGC is considered polar water and it is cold and low in salinity. The lowness in salinity has a lot to do with freshwater run off from sea ice melting, river runoff, and Pacific water flux and it is cold due to air-sea interactions while in the Arctic. Typical characteristics for the EGC Polar water are a temperature between 0 °C and –1.7 °C, and the salinity varies greatly from 30 psu to 34 psu at a 150-meter depth, the layer beneath the Polar Water is known as the Atlantic Water layer. It extends down to about 1000 m and this layer is defined as having relatively warm temperatures and saline waters. The temperatures are normally above 0 °C and have a salinity of 34 psu at 150 meters, the Atlantic water that is seen in the EGC comes from two different sources. The first source of Atlantic Water originates from westward directed Atlantic water in the West Spitsbergen Current and this current sends Atlantic water into the Fram Strait, and because it is more dense then the surface Polar water it sinks to an intermediate depth. The second source of AW in the EGC originates from recirculated AW in the Arctic and this is AW that has entered the Arctic via the North Atlantic and has been circulating in the Arctic and is now being pushed out of the Arctic via the EGC. The layer beneath the Atlantic Water is simply referred to as the Deep Water where the salinity and this level typically extends from 1000 meters to the bottom of the ocean. The temperatures in this level are normally below 0 °C. The deep water masses are recirculated within the Greenland Sea due to the Jan Mayen Fracture Zone, here, the deep water encounters the Jan Mayen Ridge and are deflected eastward towards the interior of the Greenland Sea Gyre. The upper layers are able to pass into the north of Iceland unhindered. It is important to note that these recirculated deep water masses in the Greenland Sea Gyre will be recirculated into the EGC once again in the future near Fram Strait, the general movement of the EGC is southward along the eastern Greenland continental margin. The currents are strong with annual averages of 6–12 cm/s in the upper part of the EGC with inter-annual maximums of 20–30 cm/s. It was estimated in 1991 by Hopkins et al. that the transport of water southward ranged from 2–32 sverdrups and that is quite a large variation that they attributed to the widely varying strength of the Atlantic Water flow at intermediate depths. More recent estimations of water transport in the top layers of the EGC is between 3 and 4 sverdrups, one of the most important aspects of the East Greenland Current is the amount of sea ice it exports into the North Atlantic Ocean
East Greenland Current
–
East Greenland Current
22.
Transpolar Drift Stream
–
The Transpolar Drift Stream is a major ocean current of the Arctic Ocean, transporting sea ice from the Laptev Sea and the East Siberian Sea towards Fram Strait. Drift experiments with ships like Fram or Tara showed that the drift takes between two and four years, in 1937, Pyotr Shirshov at the Soviet drift ice station North Pole-1 described this drift. The stream conveys water in two major routes to the northern Atlantic Ocean at a rate of about 1.5 miles per day. Primarily wind-driven, it flows roughly from the northern coast of Russia and Alaska and it has been cited as a major factor in the North Atlantic Oscillation and Arctic oscillation atmospheric changes. The drift typically takes one of two paths before exiting into the northern Atlantic Ocean, on decadal and longer timescales, the North Atlantic Oscillation and the Arctic Oscillation indices affect the flow pattern of the transpolar drift stream. During times of positive NAO and positive AO, there is a weak Arctic high, in this case, the drift flows from the Laptev Sea towards the Beaufort Sea before exiting the Arctic Ocean through the Fram Strait. Conversely, during periods of NAO- and AO-, there is a strong Arctic high, in this phase, the drift flows directly from the Laptev Sea through the Fram Strait. Drift Station, Arctic Outposts of Superpower Science
Transpolar Drift Stream
–
Transpolar Drift and
Beaufort Gyre are major
ocean currents within the
Arctic Ocean.
23.
Benguela Current
–
The Benguela Current /bɛŋˈɡweɪlə/ is the broad, northward flowing ocean current that forms the eastern portion of the South Atlantic Ocean gyre. The current extends from roughly Cape Point in the south, to the position of the Angola-Benguela front in the north, the current is driven by the prevailing south easterly trade winds. Inshore of the Benguela Current proper, the easterly winds drive coastal upwelling, forming the Benguela Upwelling System. The cold, nutrient rich waters that upwell from around 200–300 m depth in turn fuel high rates of phytoplankton growth, and sustain the productive Benguela ecosystem. Eddies from the warm South Indian Ocean Agulhas current along South Africas east coast do round the Cape of Good Hope from time to time to join the Bengulela current, the Benguela current is 200 to 300 km wide and widens further as it flows north and northwest. Its western, seaward edge is ill-defined, with temporary and seasonal eddies. Northward winds along the coast result in Ekman transport offshore and upwelling of nutrient rich water to the euphotic zone. The intensity of the event is determined by wind strength. Variations in wind strength cause pulses of upwelling, which propagate to the south along the coast with speeds of 5 to 8 m/s. The pulses are similar to a Kelvin wave, except on a scale of 30 to 60 km instead of 1000 km, pulses of upwelling induce biological production. In the Benguela system, phytoplankton growth requires a period of upwelling followed by a period of stratification, the phytoplankton bloom usually lags the upwelling event by 1 to 4 days and blooms for 4 to 10 days. In order for zooplankton to have a food supply, the phytoplankton blooms must not occur too far apart. Pulses of upwelling in the Benguela system regularly have a duration of 10 days, an optimal period for biological production. It is estimated that the new production in the Benguela system is 4.7 × 10^13 gC/y. The Benguela oxygen minimum zone starts around a depth of 100 m and is a few hundred meters thick, bacteria that use sulpher rather than oxygen reside in the oxygen minimum zone. The most abundant fishes in the Benguela system are Sardinops and Engraulis, Sardinops ocelata was intensely fished beginning in the 1950s and peaking in 1968 with landings over 1.3 million tons. Since then, the Sardinops fishery has declined and the Engraulis capensis fishery has taken over, similar to the Pacific El Niño, a thick slab of warm, nutrient poor water enters the northern part of the Benguela upwelling system off the Namibia coast about once per decade. During the Benguela Niño, warm, salty waters from the Angola Current move southward and this slab of warm salty water extends to 150 km offshore and to 50 m depth
Benguela Current
–
The courses of the warm Agulhas current (red) along the east coast of South Africa, and the cold Benguela current (blue) along the west coast. Note that the Benguela current does not originate from Antarctic waters in the South Atlantic Ocean, but from upwelling of water from the cold depths of the Atlantic Ocean against the west coast of the continent. The two currents do not "meet" anywhere along the south coast of Africa.
Benguela Current
–
The red areas show major upwelling areas. The Benguela Current is on the southwest coast of Africa.
24.
Brazil Current
–
The Brazil Current is a warm water current that flows south along the Brazilian south coast to the mouth of the Río de la Plata. This current is caused by diversion of a portion of the Atlantic South Equatorial Current from where that current meets the South American continent and it is a western boundary current like the Gulf Stream, and is indeed its southern counterpart, however, it is considerably shallower and weaker. It flows south from the equator to the west wind drift and it joins the Falkland Current at the Argentine Sea, making it a temperate sea
Brazil Current
–
Brazil Current in a map of the Atlantic Ocean
25.
Caribbean Current
–
The current results from the flow of the Atlantic South Equatorial Current as it flows north along the coast of Brazil. As the current turns north through the Yucatan Channel, it is renamed the Yucatan Current, the Caribbean Current water comes from the Atlantic Ocean via the North Equatorial, North Brazil, and Guiana Currents. The circulation of the Columbia-Panama Gyre flows counter-clockwise to the Caribbean Current
Caribbean Current
–
This article needs additional citations for
verification. Please help improve this article by
adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2013)
26.
Loop Current
–
Mesh analysis is a method that is used to solve planar circuits for the currents at any place in the electrical circuit. Planar circuits are circuits that can be drawn on a surface with no wires crossing each other. A more general technique, called loop analysis can be applied to any circuit, mesh analysis and loop analysis both make use of Kirchhoff’s voltage law to arrive at a set of equations guaranteed to be solvable if the circuit has a solution. Mesh analysis is easier to use when the circuit is planar. Mesh analysis works by arbitrarily assigning mesh currents in the essential meshes, an essential mesh is a loop in the circuit that does not contain any other loop. Figure 1 labels the essential meshes with one, two, and three, a mesh current is a current that loops around the essential mesh and the equations are set solved in terms of them. A mesh current may not correspond to any physically flowing current and it is usual practice to have all the mesh currents loop in the same direction. This helps prevent errors when writing out the equations, the convention is to have all the mesh currents looping in a clockwise direction. Figure 2 shows the circuit from Figure 1 with the mesh currents labeled. Solving for mesh currents instead of directly applying Kirchhoffs current law and this is because there are fewer mesh currents than there are physical branch currents. In figure 2 for example, there are six branch currents and these equations are the sum of the voltage drops in a complete loop of the mesh current. For problems more general than those including current and voltage sources, the following is the same circuit from above with the equations needed to solve for all the currents in the circuit. There are two cases in mesh current, currents containing a supermesh and currents containing dependent sources. A supermesh occurs when a current source is contained between two essential meshes, the circuit is first treated as if the current source is not there. This leads to one equation that incorporates two mesh currents, once this equation is formed, an equation is needed that relates the two mesh currents with the current source. This will be an equation where the current source is equal to one of the mesh currents minus the other, the following is a simple example of dealing with a supermesh. When a dependent source is contained within an essential mesh, the dependent source should be treated like an independent source, after the mesh equation is formed, a dependent source equation is needed. This equation is called a constraint equation
Loop Current
27.
Portugal Current
–
The Portugal Current is a weak warm water current that flows south-easterly towards the coast of Portugal. The current results from the movement of water east caused by the North Atlantic Drift, bischof, Barbie, Arthur J. Mariano, Edward H. Ryan. University of Miami Rosenstiel School of Marine and Atmospheric Science
Portugal Current
–
North Atlantic currents
28.
West Spitsbergen Current
–
The West Spitsbergen Current is a warm, salty current that runs poleward just west of Spitsbergen, in the Arctic Ocean. The WSC branches off the Norwegian Atlantic Current in the Norwegian Sea, the WSC is of importance because it drives warm and salty Atlantic Water into the interior Arctic. The warm and salty WSC flows north through the side of Fram Strait. The EGC is characterized by being cold and low in salinity. Thus, the EGC combined with the warm WSC makes the Fram Strait the northernmost ocean area having ice-free conditions throughout the year in all of the global ocean, the WSC has a unique structure as it flows poleward off the western coast of Spitsbergen. It is easiest to discuss horizontal movements and vertical movements of the WSC, specifically, it tends to follow along steep continental shelves. The current is quite narrow and strong, having a width of roughly 100 kilometers, at about 80° North latitude the WSC splits into two different sections, the Svalbard branch and the Yermak Branch. The Yermak Branch moves northwesterly till about 81°N, and then it moves directly westward, the Return Atlantic Current is directly east of the East Greenland Current. There is a current that splits off from the Yermak Branch and this current is not well understood in the literature, and thus more information is needed. It is believed this current loops back into the Svalbard Branch further along in its track eastward, after the WSC splits off from the Norwegian Atlantic Current it begins to enter very cold atmospheric conditions. This is one element of the formation of the Lower Arctic Intermediate Water, as the current continues to move northward and reaches the continental shelf of western Svalbard it begins to encounter sea-ice. The sea-ice melts due to the warmth of the WSC, winds mix the freshwater and the warm salty water of the WSC mix, creating some Arctic Surface Water. This Arctic Surface Water is now less dense than the Atlantic Water in the WSC, at this point the WSC is still relatively warm and very saline. Thus, this allows the Atlantic Water in the WSC to be isolated from the surface waters. After the current splits into the Svalbard Branch and the Yermak Branch, however, in the Yermak Branch the WSC is not able to penetrate deep inside the Arctic Ocean because the zone it enters has very strong tidal mixing. This allows the Atlantic Water to mix with the Polar Waters, creating more of a mixture of relatively warm. This extends down to about 300 meters which is recognized as the depth of the Return Atlantic Current. For the Svalbard Branch, the Atlantic Water core of the WSC continues to sink as it more and more freshwater on its eastern route
West Spitsbergen Current
–
The West Spitsbergen Current transport relative warm and saline water into the
Arctic Ocean.
29.
Agulhas Current
–
The Agulhas Current /əˈɡʌləs/ is the western boundary current of the southwest Indian Ocean. It flows down the east coast of Africa from 27°S to 40°S and it is narrow, swift and strong. The sources of the Agulhas Current are the East Madagascar Current, the Mozambique Current, the net transport of the Agulhas Current is estimated as 100 Sv. The flow of the Agulhas Current is directed by the topography, the current follows the continental shelf from Maputo to the tip of the Agulhas Bank. Here the momentum of the current overcomes the vorticity balance holding the current to the topography, the current reaches its maximum transport near the Agulhas Bank where it ranges between 95-136 Sv. The core of the current is defined as where the surface velocities reaches 100 cm/s, the mean peak speed is 136 cm/s, but the current can reach 245 cm/s. As the Agulhas Current flows south along the African east coast, it tends to bulge inshore frequently and these bulges are occasionally followed by a much larger offshore bulge, known as Natal pulses. Natal pulses move along the coast at 20 km per day, an ACM can bulge up to 20 km and a NP up to 120 km from the currents mean position. The AC passes 34 km offshore and an ACM can reach 123 km offshore, when the AC meanders, its width broadens from 88 km to 125 km and its velocity weakens from 208 cm/s to 136 cm/s. An ACM induces a strong inshore counter-current, large-scale cyclonic meanders known as Natal pulses are formed as the Agulhas Current reaches the continental shelf on the South African east-coast. As these pulses moves along the coast on the Agulhas Bank, such a ring shedding can be triggered by a Natal pulse alone, but sometimes meanders on the Agulhas Return Current merge to contribute to the shedding of an Agulhas ring. This water becomes the Agulhas Return Current, rejoining the Indian Ocean Gyre and it is estimated that up to 85 Sv of the net transport is returned to the Indian Ocean through the retroflection. The remaining water is transported into the South Atlantic Gyre in the Agulhas Leakage, along with direct branch currents, this leakage takes place in surface water filaments, and Agulhas Eddies. It is estimated that as much as 15 Sv of Indian Ocean water is leaked directly into the South Atlantic,10 Sv of this is relatively warm, salty thermocline water, with the remaining 5 Sv being cold, low salinity Antarctic Intermediate Water. Since Indian Ocean water is warmer and saltier than South Atlantic water. This heat flux is believed to contribute to the rate of evaporation in the South Atlantic. It should be noted that an amount of the Agulhas Leakage joins the North Brazil Current. Surface water filaments are estimated to account for up to 13% of the total salt transport from the Agulhas Current into the Benguela Current, due to surface dissipation, these filaments are not believed to significantly contribute to inter-basin heat flux
Agulhas Current
30.
Agulhas Return Current
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The Agulhas Return Current is an ocean current in the South Indian Ocean. The ARC contributes to the exchange between oceans by forming a link between the South Atlantic Current and the South Indian Ocean Current. It can reach velocities of up to 4 knots and is popular among participants in trans-oceanic sailing races. The Agulhas Current follows the continental shelf of the African east-coast, pass through the Agulhas Passage until it leaves the Agulhas Bank and reaches the Agulhas Basin south of South Africa. From there it retroflects almost completely back into the south Indian Ocean as the ARC, the water mass loses a lot of heat at the Agulhas Retroflection, up to 200 W/m3, while evaporation and precipitation change the composition of the upper layers. The ARC, therefore, has another composition than the Agulhas Current proper and it also loses velocity from 110–75 cm/s and volume transport from 70 to 54 million m³/s. Furthermore, all traces of Indian Tropical Surface Water are gone, having left the retroflection, the ARC meanders east between 36°S and 41°S. These meanders were described as Rossby waves in 1970 and are known to shed cold eddies equatorward, the ARC makes a large, quasi-permanent northward meander around the Agulhas Plateau after which it loses more velocity and volume by leakage into the South Indian subtropical gyre. Over the Crozet Basin the last remnants of the ARC are gone, as it enters the Crozet Basin at 53°E, the transport of the ARC is 35 Sv, most of which is recirculated northward before reaching the Kerguelen-Amsterdam Passage. The current east of the Crozet Basin, at 66°E-70°E, is called the South Indian Ocean Current and lacks the distinctive features of the ARC
Agulhas Return Current
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The Agulhas Return Current (ARC) meanders east from the southern tip of Africa
31.
Indonesian Throughflow
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From the Banda Sea the ITF exits Timor, Ombai, and Lombok passages. The location and topography of the channels that make up the ITF are shown in the Figure, Lombok Strait is 300m deep and roughly 35 km wide and the currents vary between 0.286 m/s eastward to 0.67 m/s westward and average 0.25 m/s westward. Currents in Ombai vary between 0.12 m/s eastward to 0.16 m/s westward, averaging 0.11 m/s westward and are funneled within the 1250m deep and 35 km wide passage. Timor passage, which is 1890 m deep by 160 km wide, is the widest of the exit pathways, flow in through Makassar and Lifamatola sums to 12.7 Sv. Total outflow transport corresponds to 15.0 Sv and is made up of Lombok, Ombai, heat Transport of the Indonesian Throughflow is 1.087 PW. Circulation and transport within the Indonesian Seas varies along with large-scale monsoon flow, another way to think about it is that downwelling on the Indian Ocean side increases sea level and so reduces the normal Pacific-to-Indian pressure head reducing the flow. Global-scale, ocean waves such as equatorial/coastal Kelvin and Rossby waves drive interannual variation of the ITF with an amplitude of roughly +/-3 Sv, upwelling associated with Rossby waves on the Pacific side reduces the Pacific-to-Indian pressure gradient and reduces the ITF. Interannual variability of Indian Ocean westerlies act in the manner as the seasonal equatorial Kelvin waves to reduce the normal westward ITF flow as well. When the Indonesian Throughflow enters the Indian Ocean it is advected towards Africa within the Indian South Equatorial Current, there it eventually exits the Indian Ocean with the Agulhas Current around South Africa into the Atlantic Ocean. So the Indonesian Throughflow transports a significant amount of Pacific Ocean heat into the southwest Indian Ocean, Ocean gyre Throughflow The Indonesian Throughflow at whoi. edu
Indonesian Throughflow
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Schematic of the ITF. Values of the flow and the major passages are indicated by red. Water enters the ITF from the western Pacific and exits into the Indian Ocean.
32.
Leeuwin Current
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The Leeuwin Current is a warm ocean current which flows southwards near the western coast of Australia. It rounds Cape Leeuwin to enter the south of Australia where its influence extends as far as Tasmania. Its strength varies through the year, it is weakest during the months from November to March when the winds tend to blow strongly from the south west northwards. The greatest flow is in the autumn and winter when the winds are weakest. Evaporation from the Leeuwin current during this period contributes greatly to the rainfall in the southwest region of Western Australia. Typically the Leeuwin Currents speed and its eddies are about 1 knot, although speeds of 2 knots are common, and the highest speed ever recorded by a drifting satellite-tracked buoy was 3.5 knots. The Leeuwin Current is shallow for a current system, by global standards, being about 300 m deep. Because of the Leeuwin Current, the shelf waters of Western Australia are warmer in winter and cooler in summer than the corresponding regions off the other continents. The ‘core’ of the Leeuwin Current can generally be detected as a peak in the temperature with a strong temperature decrease further offshore. The surface temperature difference across the Current is about 1°C at North West Cape, 2° to 3° at Fremantle, the current frequently breaks out to sea, forming both clockwise and anti-clockwise eddies. The existence of the current was first suggested by William Saville-Kent in 1897, Saville-Kent noted the presence of warm tropical water offshore in the Houtman Abrolhos, making the water there in winter much warmer than inshore at the adjacent coast. The existence of the current was confirmed over the years, but not characterised and named until Cresswell, Western fisheries magazine, Winter 2000, p. 47-49 Ocean current Oceanic gyres Physical oceanography West Australian Current Climate change threatening the Southern Ocean. CSIRO Marine Research Rottnest Island context
Leeuwin Current
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CSIRO NOAA polar orbiting satellites obtain the data generating sea surface temperature images. (Composite 15 day image showing the extension of the Leeuwin Current around Tasmania)
Leeuwin Current
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Ocean Currents surrounding Australia. The Leeuwin Current can be seen off the Western Australian Coast
Leeuwin Current
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Data from two satellite instruments is used in constructing this image of the Leeuwin Current. Sea surface temperature information comes from the US NOAA 14 satellite while the surface current velocity is derived from sea level measurements made by the satellite-borne altimeter. Sea level data from the US/French Topex/Poseidon and European ERS altimeters are combined
33.
Mozambique Current
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The classical definition of the Mozambique Current is that it is a strong, steady, western boundary current. Modern research has challenged that assumption, and indicates that rather than a western boundary current. Direct evidence for these eddies has been found in satellite altimetry data, ship borne surveys, nonetheless, it is impossible to rule out the possibility that the Mozambique Current may appear intermittently, for short durations. Indeed, numerical simulations in the Mozambique Channel show the appearance of a current on the Mozambican Coast. Mozambique Channel Eddies are large, warm, anti-cyclonic eddies that propagate southwards in the Mozambique Channel and these eddies may have diameters of up to 300 km, and maximum swirl velocities of nearly 1 m/s. The exact causal mechanism, and location of the formation is still debated. The frequency of eddy occurrence reduces from around seven per year in the north of the Channel, once the eddies exit the Mozambique Channel, they contribute to the variability of the Agulhas Current, including the generation of the Natal Pulse, and Agulhas Rings
Mozambique Current
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visualisation of ocean currents
34.
Somali Current
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The Somali Current is an ocean boundary current that runs along the coast of Somalia and Oman in the Western Indian Ocean and is analogous to the Gulf Stream in the Atlantic Ocean. This current is heavily influenced by the monsoons and is the major upwelling system that occurs on a western boundary of an ocean. The water that is upwelled by the current merges with another upwelling system, the Somali current is characterized by seasonal changes influenced by the Southwest monsoon and the Northeast Monsoon. During the months of June to September, the warm Southwest monsoon moves the coastal waters northeastward, the upwelled water is carried offshore by Ekman transport and merges with water that was brought to the surface by open-ocean upwelling. The Findlater jet, a narrow low-level, atmospheric jet, also develops during the Southwest monsoon, as a result, an Ekman transport is created to the right of the wind. At the center of the jet, the transport is maximum and decreases to the right, to the left of the jet center, there is less water movement toward the center than is leaving, creating a divergence in the upper layer and resulting in an upwelling event. In contrast, to the right of the center of the jet and this open-ocean upwelling in combination with the coastal upwelling cause a massive upwelling. The Northeast monsoon, which occurs from December to February, causes a reversal of the Somalia current, cooler air causes the surface water to cool and creates deep mixing, bringing abundant nutrients to the surface. The history of physical oceanographic approaches to the Somali current has begun from the mid 1960s with serious interests, from the mid-1960s until the late 1970s several magnificent theoretical studies had been proposed and gave physical answers of the current behaviors and formations. After the late 1970s, the physics of the Somali current enhanced by ocean data analyses with outstanding field measurements of the current properties, the research footprints during the early 1960s to the late 1970s are presented as below. Oceanographers and Meteorologists agreed the existence of the Somali current and its behaviors,1969 Lighthill, the source of the Somali current is mass flux deposited by baroclinic and barotropic waves in the western boundary region. 1970 Düing, presented the presence of alternative cyclonic and anti-cyclonic gyre, the Somali Current is rapid response, shallow and shifts its direction seasonally. Especially from 5°N and southward, the Somali current is extremely shallow, further north, the jet deepens somewhat, reaching the permanent thermocline. The structure of the current around the equator is extremely complex and similarly layered to the equatorial flows, the typical water volume transported by the Somali Current amounts to 37+/-5 Sv, making the current circulation generally weaker than other mid-latitude western boundary currents. However, volume transport maxima as high as 60-70 Sv have been measured around the south of Socotra Island, the Somali Current is driven principally by the seasonal monsoon winds. In summer the southwest monsoon blows along the east coast of Africa, during the fall it reverses its direction to become a northeasterly wind during winter. Before the onset of the monsoon, During this season, shallow northward coastal current flows with 50–100 km width near the Somali coast, by alongshore winds, upwelling current flows to the coast. Near the equator, the East African Coast Current flows northward across the equator, the southern Somali Current flows northward as an extension of the EACC from south to the 3-4°N
Somali Current
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Southward Somali Current during Northeast Indian Monsoon
35.
West Australian Current
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The West Australian Current, is a cool surface current of the Southern Ocean and Southern Indian Ocean. It starts as the Southern Indian Ocean Current, a part of the larger Antarctic Circumpolar Current, as the current approaches Western Australia, it turns north, parallel to the western coast of Australia, and becomes the West Australian Current. The current is mainly seasonal, being weaker in winter and stronger in summer and these 3 currents together contribute greatly to the rainfall and climate in the southwest region of Western Australia. Ocean current Oceanic gyres Physical oceanography
West Australian Current
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Ocean Currents surrounding Australia. The West Australian Current is located where the
Leeuwin Current is labeled and flows in the opposite direction to the Leeuwin Current
36.
California Current
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It is considered an Eastern boundary current due to the influence of the North American coastline on its course. It is also one of five major coastal currents affiliated with upwelling zones, the others being the Humboldt Current, the Canary Current, the Benguela Current, and the Somali Current. The California Current is part of the North Pacific Gyre, a large swirling current that occupies the northern basin of the Pacific. For example, Half Moon Bay at 37 degrees latitude has no month with a high above 67 °F. Additionally, extensive upwelling of colder sub-surface waters occurs, caused by the northwesterly winds acting through the Ekman Effect. The winds drive surface water to the right of the flow, that is offshore. The upwelling further cools the already cool California Current and this is the mechanism that produces Californias characteristic coastal fog and the negative temperature anomaly measured in Californias coastal waters during summer. This translates into cold coastal waters during the summer, stretching from Oregon to Baja California and this does not include the coastal water surrounding San Diego, where a warm water anomaly occurs. The cold water is highly due to the upwelling, which brings to the surface nutrient-rich sediments, supporting large populations of whales, seabirds. Winds of the direction and strength to induce upwelling are more prevalent in the presence of Eastern boundary currents. Phytoplankton production is increased in these areas because the nutrient-rich water lying below the pycnocline is relatively close to the surface and is thus easily upwelled. Scientists at Scripps Institution of Oceanography said in 2011 that the surface temperature of the water at Scripps Pier has increased by almost 3 degrees since 1950. The Bakun upwelling index is based on a 20-year average of the monthly mean Ekman transport for different regions off the California coast and it ranges from 300 meters-cubed/second to −212 meters-cubed/second. There is year-round upwelling off Southern Californias coast, but it is strongest in the summer months, off the coast of Oregon and Washington, there is forceful downwelling in the winter months, and upwelling in the region is restricted to the months of April through September. Primary production is a topic of interest among those who study the California Current, in their study, Hayward and Venrick found great variability in both biomass and the productivity of phytoplankton in the California Current. The differences observed by Hayward and Venrick in carbon-fixation rates show the nature of the California Current. Several studies have investigated the carbon flow from primary production to the fish stocks which depend on the California Current. Lasker described powerful jets and squirts off northern and central California and these jets and squirts move large quantities of cold, nutrient rich water offshore
California Current
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The lack of clouds along the coast (and also along the Central Valley of California) is due to an offshore wind blowing drier air from the land offshore.
California Current
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The ocean currents.
37.
East Australian Current
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The East Australian Current is the southward western boundary current that is formed from the South Equatorial Current crossing the Coral Sea and reaching the eastern coast of Australia. At around 15° S near the Australian coast the SEC divides forming the flow of the EAC. It is the largest ocean current close to the shores of Australia, the EAC reaches a maximum velocity at 30° S where its flow can reach 90 cm/s. As it flows southward it splits from the coast at around 31° to 32° S, by the time it reaches 33° S it begins to undergo a southward meander while another portion of the transport turns back northward in a tight recirculation. At this location the EAC reaches its maximum transport of nearly 35 Sv, the majority of the EAC flow that does not recirculate will move eastward into the Tasman Front crossing the Tasman Sea just north of the cape of New Zealand. The Tasman Front transport is estimated at 13 Sv, the eastward movement of the EAC through the Tasman Front and reattaching to the coastline of New Zealand forms the East Auckland Current. The EAC also acts to transport tropical marine fauna to habitats in sub-tropical regions along the south east Australian coast, in the 2003 Disney/Pixar animated film Finding Nemo, the EAC is portrayed as a superhighway that fish and sea turtles use to travel down the east coast of Australia. The characters Marlin and Dory join a group of sea turtles in using the EAC to help them travel to Sydney Harbour, the basic premise of this storyline is correct. Every summer, thousands of fish are swept from the Great Barrier Reef to Sydney Harbour, ocean current Oceanic gyres Physical oceanography Image of the East Australian Current. Sea surface temperature and currents, New South Wales
East Australian Current
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Thermal profile of the East Australian Current
East Australian Current
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CSIRO NOAA polar orbiting satellites obtain the data generating sea surface temperature images. (Composite 15 day image showing the extension of the Leeuwin Current around Tasmania)
38.
Humboldt Current
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The Humboldt Current is a cold, low-salinity ocean current that flows north along the west coast of South America from the southern tip of Chile to northern Peru. Also called the Peru Current, it is an eastern boundary current flowing in the direction of the equator and it is the most productive marine ecosystem in the world, as well as the largest upwelling system. The Humboldt’s high rates of primary and secondary productivity support the world’s largest fisheries, approximately 18-20% of the world’s fish catch comes from the Humboldt Current LME. The species are pelagic, sardines, anchovies and jack mackerel. The LME’s high productivity supports other important fishery resources as well as marine mammals, the cold, nutrient-rich water brought to the surface by upwelling drives the system’s extraordinary productivity. Periodically, the upwelling that drives the system’s productivity is disrupted by the El Niño-Southern Oscillation event, when this occurs, fish abundance and distribution are significantly affected, often leading to stock crashes and cascading social and economic impacts. These events have led to changes, where sardines and anchovies have replaced each other periodically as the dominant species in the ecosystem. These species changes can have consequences for the fishing industry. The Humboldt has a cooling influence on the climate of Chile, Peru. It is also responsible for the aridity of Atacama Desert in northern Chile and coastal areas of Peru. Marine air is cooled by the current and thus is not conducive to generating precipitation
Humboldt Current
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Humboldt Current
Humboldt Current
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La Silla is in the Southern outskirts of the
Atacama Desert, one of the driest places on Earth, it may come as a surprise to see cloud formations result of the Peruvian Humboldt Current.
Humboldt Current
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Fisheries science
Humboldt Current
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Management
39.
Kuroshio Current
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The Kuroshio is a north-flowing ocean current on the west side of the North Pacific Ocean. It is similar to the Gulf Stream in the North Atlantic and is part of the North Pacific ocean gyre, like the Gulf stream, it is a strong western boundary current. It begins off the east coast of Luzon, Philippines, Taiwan and flows northeastward past Japan and it is analogous to the Gulf Stream in the Atlantic Ocean, transporting warm, tropical water northward toward the polar region. It is sometimes known as the Black Stream — the English translation of kuroshio, the path of Kuroshio south of Japan is reported every day. Its counterparts are the North Pacific Current to the north, the California Current to the east, the warm waters of the Kuroshio Current sustain the coral reefs of Japan, the northernmost coral reefs in the world. The branch into the Sea of Japan is called Tsushima Current, western boundary currents transport organisms long distances rapidly and a variety of commercially important marine organisms migrate in these currents in the course of completing their lives. Subtropical gyres occupy a fraction of the worlds ocean and are more productive than originally thought. In addition, their fixation of carbon dioxide is an important factor in the budget for carbon dioxide in the atmosphere. Satellite images of the Kuroshio Current illustrate how the current path meanders, eddies retain their unique form for several months and have their own biological characteristics that depend on where they form. The eddies size and strength decline with distance from major ocean currents, the amount of energy decreases from the rings associated with the major currents and down to eddies remote from those currents. Cyclonic eddies have the potential to cause upwelling that would affect the global primary-production budget, upwelling brings cold, nutrient-rich water to the surface resulting in an increase in productivity. The biological consequences for fish populations that inhabit the shelf are quite large. The Kuroshio is a warm current—24 °C annual average sea-surface temperature—about 100 kilometres wide, the coastal areas are highly productive and the maximum chlorophyll value is found around 100 metres depth. There are indications that eddies contribute to the preservation and survival of fish larvae transported by the Kuroshio, plankton biomass fluctuates yearly and is typically highest in the eddy area of the Kuroshio’s edge. Warm-core rings are not known for having high productivity, however, the biology of the warm-core rings from the Kuroshio Current show results of productivity equally distributed throughout for a couple of reasons. One is upwelling at the periphery, the other is the convective mixing caused by the cooling of water as the ring moves north of the current. The thermostad is the mixed layer that has discrete boundaries. Within this layer, nutrient-rich water is brought to the surface, there are many complex interactions with the warm-core ring and thus lifetime productivity is not very different from the surrounding shelf water
Kuroshio Current
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The
Oyashio Current colliding with the Kuroshio Current near
Hokkaido. When two currents collide, they create
eddies.
Phytoplankton growing in the surface waters become concentrated along the boundaries of these eddies, tracing out the motions of the water.
Kuroshio Current
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The Kuroshio Current is the west side of the clockwise North Pacific
ocean gyre
40.
North Pacific Current
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The North Pacific Current is a slow warm water current that flows west-to-east between 40 and 50 degrees north in the Pacific Ocean. The current forms the part of the North Pacific Subpolar Gyre. The North Pacific Current forms the part of the North Pacific Subtropical Gyre. In the eastern North Pacific near southern British Columbia, it splits into the southward California Current, flowing easterly from the island of Honshu, Japan, the North Pacific Current covers over 20° of longitude. According to the Great Soviet Encyclopedia the NPC is often considered to be a part of the Kuroshio current, the current covers a large area bringing the warmer latitudinal waters up into the sub-polar latitudes causing a temperature differential of nearly 48.2 F°. The average sea temperature along the NPC can range in the winter from 45-61°F. Along the NPC path from west to east the current begins to slow in velocity to around 0.1 m/s, as the NPC approaches the Northwestern coast of North America it divides into two currents the Alaska and California current. The Gulf of Alaska and the California Current receive different volumes and this division of water flow is known as bifurcation The Gulf of Alaska receives about 60% of the water from the NPC and the California Current receives approximately the other 40% of the NPC water. These volumes do fluctuate, however the result in increased volumes and velocities of the NPC water entering into these currents. The NPC is the Northern boundary current that forms the North Pacific Subtropical Gyre, as a shoot off of the Kuroshio the NPC slows during its westward flow to the Americas. However, the NPC maintains enough momentum to bound the northern edge of the gyre, the North Pacific Gyre is estimated to be 7-9 million square miles. Debris from the ocean can become isolated into the center of the gyres as well as being distributed along the perimeter, debris from the Japanese earthquake of 2011 has been found on the shores of Canada, Alaska, and Washington. Quick Bulletin of Ocean Conditions around Japan
North Pacific Current
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The North Pacific Current.
41.
Oyashio Current
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Oyashio, also known as Oya Siwo, Okhotsk or the Kurile current, is a cold subarctic ocean current that flows south and circulates counterclockwise in the western North Pacific Ocean. It collides with the Kuroshio Current off the shore of Japan to form the North Pacific Current. The nutrient-rich Oyashio is named for its role as the parent that provides for. However, the Oyashio Current also causes Vladivostok to be the most equatorward port to seasonally freeze, nonetheless, this has relatively little effect on the fish yield through the Sea of Okhotsk, because the large tides mean freezing does not occur so easily. During glacial periods, when sea level exposed the Bering land bridge. The level of cooling with the onset of glacial conditions was much less than in areas of the Earth at similar latitudes. Ocean current Oceanic gyres Physical oceanography Japanese destroyer Oyashio, the Imperial Japanese Navy destroyer named after the current, taylor and Francis, ISBN 90-5410-706-5, pp 367–8. Regional Definition page for the Oyashio Current, UNEP Global International Waters Assessment, accessed 2 July 2010
Oyashio Current
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The Oyashio Current colliding with the
Kuroshio Current near
Hokkaido. When two currents collide, they create
eddies.
Phytoplankton growing in the surface waters become concentrated along the boundaries of these eddies, tracing out the motions of the water.
42.
Antarctic Circumpolar Current
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The Antarctic Circumpolar Current is an ocean current that flows clockwise from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift, the ACC is the dominant circulation feature of the Southern Ocean and has a mean transport of 100-150 Sverdrups, making it the largest ocean current. More recent research puts this number at over 173 Sv. The current is due to the lack of any landmass connecting with Antarctica. Associated with the Circumpolar Current is the Antarctic Convergence, where the cold Antarctic waters meet the waters of the subantarctic. These nurture high levels of phytoplankton with associated copepods and krill, and resultant foodchains supporting fish, whales, seals, penguins, albatrosses and a wealth of other species. The clipper route, which is the fastest sailing route around the world, the current creates the Ross and Weddell gyres. The ACC connects the Atlantic, Pacific and Indian Oceans, the current is strongly constrained by landform and bathymetric features. Passing through the Indian Ocean, the current first retroflects the Agulhas Current to form the Agulhas Return Current before it is split by the Kerguelen Plateau, deflection is also seen as it passes over the mid-ocean ridge in the Southeast Pacific. The current is accompanied by three fronts, the Subantarctic front, the Polar front, and the Southern ACC front, furthermore, the waters of the Southern Ocean are separated from the warmer and saltier subtropical waters by the subtropical front. The northern boundary of the ACC is defined by the edge of the SAF. Still further south lies the PF, which is marked by a transition to cold, relatively fresh. Here a temperature minimum is allowed by salinity dominating density stratification, further south still is the SACC, which is determined as the southernmost extent of Circumpolar Deep Water. This water mass flows along the shelfbreak of the western Antarctic Peninsula and thus marks the most southerly water flowing through Drake Passage, the bulk of the transport is carried in the middle two fronts. The total transport of the ACC at Drake Passage is estimated to be around 135 Sv, or about 135 times the transport of all the worlds rivers combined. There is a small addition of flow in the Indian Ocean, with the transport south of Tasmania reaching around 147 Sv. The circumpolar current is driven by the westerly winds in the latitudes of the Southern Ocean. In latitudes where there are continents, winds blowing on light surface water can pile up light water against these continents
Antarctic Circumpolar Current
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The Antarctic Circumpolar Current is the strongest current system in the world oceans and the only ocean current linking all major oceans: the Atlantic, Indian and Pacific Oceans. Seawater density fronts after Orsi, Whitworth & Nowlin 1995.
Antarctic Circumpolar Current
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The
Falkland Current transports nutrient-rich cold waters from the ACC north towards the
Brazil–Malvinas Confluence. Phytoplankton chlorophyll concentration are shown in blue (lower concentrations) and yellow (higher concentrations).
43.
Indian Ocean Gyre
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The Indian Ocean gyre, located in the Indian Ocean, is one of the five major oceanic gyres, large systems of rotating ocean currents, which together form the backbone of the global conveyer belt. The Indian Ocean gyre is composed of two currents, the South Equatorial Current, and the West Australian Current. Normally moving counter-clockwise, in the winter the Indian Ocean gyre reverses direction due to the winds of the South Asian Monsoon. In the summer, the land is warmer than the ocean, however, during the winter, these temperatures reverse, making the winds blow from the land to the ocean. Because most of the air pressure gradient is retained behind the Tibetan plateau, air pressure gradients over the Indian Ocean and this results in winds of moderate strength, due to the protection from the full force winds blowing off the Mongolian high pressure region. Because of these moderate, dry winds, the Winter Monsoon season in the Indian Ocean region is the dry season for most of Southern Asia. Due to this seasonal wind cycle, the currents of the Indian Ocean, like the other gyres, it contains a garbage patch. A garbage patch is a region of marine debris within the water column that circulate the gyre constantly. The Indian Ocean’s garbage patch covers an area, at least five million square kilometers. As garbage patches such as these circulate for long periods of time, in the Indian Ocean gyre, the garbage patch has been more of a mystery. Having just been discovered in 2010, it is still under research and it is known, however, that like most garbage patches, it is very fluid, and changes with the seasons, making its location difficult to pinpoint. It seems to circulate with the Indian Ocean gyre, from the Australian side to the African side, down the African coast, and then back to Australia. According to the team who discovered the garbage patch, the rotation of the gyre’s garbage patch takes about six years, until it reaches the center of the gyre
Indian Ocean Gyre
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The Indian Ocean Gyre
44.
North Atlantic Gyre
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The North Atlantic Gyre, located in the Atlantic Ocean, is one of the five major oceanic gyres. This gyre is similar to the North Pacific Gyre in the way it traps man-made marine debris in the North Atlantic Garbage Patch, the North Atlantic Gyre forms the Sargasso Sea, noted for its still waters and dense seaweed accumulations. As with many patterns, the North Atlantic Gyre experiences seasonal changes. Stramma and Siedler determined that the gyre expands and contracts with a variance, however. During the Northern Hemisphere winter season, the gyre follows a more zonal pattern, as the seasons move from winter to summer, the gyre shifts south by a few degrees latitude. This occurs concurrently with the displacement of the part of the gyre. It has been concluded that zonal deviations within the gyre remain small while north and south of the gyre they are large. Data collected in the Sargasso Sea region in the part of the North Atlantic Gyre has led to analytical evidence that the variability of this gyre is linked to wintertime convective mixing. According to Bates, a variation of 8-10 °C in surface temperature occurs alongside a fluctuation in the mixed layer depth between the Northern Hemisphere winter and summer seasons. The depth rises from 200 meters in winter to about 10 meters in summer, nutrients remain below the euphotic zone for most of the year, resulting in low primary production. Yet during winter convective mixing, nutrients penetrate the euphotic zone and this then lifts the mixed-layer depth to 10 meters. The changes in oceanic biology and vertical mixing between winter and summer in the North Atlantic Gyre seasonally alter the amount of carbon dioxide in the seawater. Interannual trends have established that carbon dioxide concentrations within this gyre are increasing at a rate to that occurring in the atmosphere. This discovery concurs with that made in the North Pacific Gyre, the North Atlantic Gyre also undergoes temperature changes via atmospheric wave patterns. The North Atlantic Oscillation is one such pattern, during its positive phase, the gyre warms. This is due to a weakening of the winds, resulting in reduced wind stress and heat exchange. Collections of aerosols, marine particles, and ocean water in the North Atlantic Gyre from 1990-1992 have led to measurements in lead isotope ratios, the surface layers of the Sargasso Sea were used to estimate the lead isotopic concentrations. 42-57% of the lead isotope concentrations result from American industrial and automotive contamination, despite the reduction in the production, however, lead concentrations from measurements made after 1992 show a decrease in the amount of lead contamination
North Atlantic Gyre
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View of the currents surrounding the gyre.
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South Atlantic Gyre
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The South Atlantic Gyre is the subtropical gyre in the south Atlantic Ocean. In the southern portion of the gyre, northwesterly winds drive eastward-flowing currents that are difficult to distinguish from the boundary of the Antarctic Circumpolar Current. Like other oceanic gyres, it collects vast amounts of floating debris, South of this gyre is the Antarctic Circumpolar Current. This current flows from West to East around Antarctica, another name for this current is the West Wind Drift. This current allows Antarctica to maintain its huge ice sheet by keeping warm ocean waters away, at approximately 125 Sv, this current is the largest ocean current. The Brazil Current is the western boundary current of the gyre and it flows south along the Brazilian coast to the Rio de la Plata. The current is considerably weaker than its North Atlantic counterpart, the Gulf Stream, Ocean current Volta do mar Ocean currents Ocean currents
South Atlantic Gyre
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A
tristan thrush on
Inaccessible Island, strewn with oceanic trash.
South Atlantic Gyre
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The South Atlantic Gyre on 1943 map.
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North Pacific Gyre
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The North Pacific Gyre, located in the northern Pacific Ocean, is one of the five major oceanic gyres. This gyre covers most of the northern Pacific Ocean and it is the largest ecosystem on Earth, located between the equator and 50° N latitude, and comprising 20 million square kilometers. It is the site of an unusually intense collection of marine debris. Ecosystem of the North Pacific Subtropical Gyre North Atlantic Garbage Patch Great Pacific Garbage Patch Ocean current Marine Pollution South Atlantic Gyre Ocean currents
North Pacific Gyre
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The main ocean currents involved with the North Pacific Gyre
