1.
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
2.
Ocean current
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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
3.
Atlantic Ocean
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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
4.
Ocean gyre
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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
5.
Cape Point
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Table Mountain and the city of Cape Town are close to the northern extremity of the same peninsula. The cape is located at 34°21′26″S 18°29′51″E, about 2.3 kilometres east, the peak above Cape Point is higher than that above the Cape of Good Hope. The rugged sandstone ridge that rises from Cape Point at sea level develops into two peaks, there is a major peak that dominates the skyline locally but there is also a smaller peak about 100 m further south. The higher peak has the old lighthouse on the top, from the end of the railway a second path leads to the lower peak. Secondly, foggy conditions often prevail at the levels, making the older lighthouse invisible to shipping. On 18 April 1911, the Portuguese liner Lusitania was wrecked just south of Cape Point at 34°23′22″S 18°29′23″E on Bellows Rock for precisely this reason, prompting the relocation of the lighthouse. The new lighthouse, located at 34°21′26″S 18°29′49″E, cannot be seen from the West until ships are at a distance to the South. The light of the new Cape Point lighthouse is the most powerful on the South African coast, with a range of 63 miles, Cape Point is situated within the Table Mountain National Park, within a section of the park referred to as Cape of Good Hope. This section covers the whole of the tip of the Cape Peninsula. The Cape of Good Hope section of the park is generally wild, the vegetation at Cape Point consists primarily of Peninsula Sandstone Fynbos. Cape Point is often claimed to be the place where the cold Benguela Current of the Atlantic Ocean. In fact, the meeting point fluctuates along the southern and southwestern Cape coast, the two intermingling currents help to create the micro-climate of Cape Town and its environs. Contrary to popular mythology, the point of the currents produces no obvious visual effect. There are, however, strong and dangerous swells, tides and localized currents around the point and these troubled seas have witnessed countless maritime disasters in the centuries since ships first sailed here. Fishing is good along the coast but the unpredictable swells make angling from the very dangerous. Over the years scores of fishermen have been swept to their deaths from the platforms by freak waves. False Bay, which opens to the east and north of Cape Point, is the location of the naval port of Simons Town. The bay is also famous - or infamous - for its great white sharks, Cape Point is the site of one of the Global Atmosphere Watchs atmospheric research stations
6.
Angola
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Angola /æŋˈɡoʊlə/, officially the Republic of Angola, is a country in Southern Africa. It is the seventh-largest country in Africa and is bordered by Namibia to the south, the Democratic Republic of the Congo to the north, Zambia to the east, and the Atlantic Ocean to west. The exclave province of Cabinda has borders with the Republic of the Congo, the capital and largest city of Angola is Luanda. In the 19th century, European settlers slowly and hesitantly began to themselves in the interior. As a Portuguese colony, Angola did not encompass its present borders until the early 20th century, following resistance by groups such as the Cuamato, the Kwanyama and the Mbunda. Independence was achieved in 1975 under a communist one-party state backed by the Soviet Union, however, the country soon descended into an even lengthier civil war that lasted until 2002. It has since become a relatively stable presidential republic. Angola has vast mineral and petroleum reserves, and its economy is among the fastest growing in the world, Angolas economic growth is highly uneven, with the majority of the nations wealth concentrated in a disproportionately small sector of the population. Angola is a state of the United Nations, OPEC, African Union, the Community of Portuguese Language Countries, the Latin Union. A highly multiethnic country, Angolas 25.8 million people span various tribal groups, customs, Angolan culture reflects centuries of Portuguese rule, namely in the predominance of the Portuguese language and the Catholic Church, combined with diverse indigenous influences. The name Angola comes from the Portuguese colonial name Reino de Angola, the toponym was derived by the Portuguese from the title ngola held by the kings of Ndongo. Ndongo was a kingdom in the highlands, between the Kwanza and Lukala Rivers, nominally tributary to the king of Kongo but which was seeking greater independence during the 16th century, modern Angola was populated predominantly by nomadic Khoi and San prior to the first Bantu migrations. The Khoi and San peoples were neither pastoralists nor cultivators, following a hunter-gatherer lifestyle and they were displaced by Bantu peoples arriving from the north, some of whom likely originated in northwestern Nigeria. Bantu speakers introduced the cultivation of bananas and taro, as well as large herds, to Angolas central highlands. During this time, the Bantu established a number of entities in most of what today comprises Angola. To its south lay the Kingdom of Ndongo, from which the area of the later Portuguese colony was known as Dongo. The region now known as Angola was reached by the Portuguese explorer Diogo Cão in 1484, the year before, the Portuguese had established relations with the Kongo, which stretched at the time from modern Gabon in the north to the Kwanza River in the south. The Portuguese established their primary trading post at Soyo, which is now the northernmost city in Angola apart from the Cabinda exclave
7.
Benguela
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Benguela is a city in western Angola, south of Luanda, and capital of Benguela Province. It lies on a bay of the name, in 12° 33’ S. 13° 25’ E. Benguela is one of Angolas most populous cities. Benguela, a Portuguese fort from 1587, was founded in 1617 by the Portuguese under Manuel Cerveira Pereira and it was long the centre of an important trade, especially in slaves to Brazil and Cuba. Ships anchored about 1.6 kilometres off the shore, in depths of 7 to 11 metres, however the nearby deep-water sheltered harbour of Lobito was a much larger port. Besides the churches of S. Felipe and S. António, the hospital, a short way beyond Benguela is Baía Farta, where salt was manufactured and sulphur was extracted. Close to Baia Farta was the beach of Baia Azul, the city prospered and grew in the following decades. Starting in the early 20th century, Benguela attracted, developed, sisal and fishing industries expanded and the financial, construction and services market boomed until 1974. In 1975, after the April 1974 Carnation Revolution in Lisbon, Portugal, in the mid-2000s, with a more peaceful environment, restoration of the railway between Benguela and Huambo commenced. In 1983 Benguela had a population of 155,000, during the civil war the city of Benguela increased its population due to refugees from the countryside. While the colonial part of the city consists of relatively good-quality houses, Benguela was one of the centres of Portuguese trade to the African interior. The city remains an important commercial link between western and eastern Angola, coffee, corn, sisal, sugarcane, and tobacco are grown in the interior regions of Angola and widely traded in Benguela. Manganese from the interior is also traded in Benguela, industries local to the city include fish processing and the milling of sugarcane, the city also produces pottery, soap, and tools. Foreign trade is handled through the port of Lobito, which is located 29 kilometres north of Benguela. Lobito, once the busiest port in Angola, was disrupted during the Angolan Civil War. The port has since revived and supports trade in the Benguela region, the city formerly had a German school, Deutsche Schule Benguela. Leila Lopes - actress and Miss Universe 2011 Benguela Airport Benguela Railway Port of Lobito
8.
Upwelling
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The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. Due to the biomass of phytoplankton and presence of water in these regions, upwelling zones can be identified by cool sea surface temperatures. The increased availability in upwelling regions results in levels of primary productivity. Approximately 25% of the global marine fish catches come from five upwellings that occupy only 5% of the total ocean area. Upwellings that are driven by coastal currents or diverging open ocean have the greatest impact on nutrient-enriched waters, the three main drivers that work together to cause upwelling are wind, Coriolis effects, and Ekman transport. They operate differently for different types of upwelling, but the effects are the same. In the overall process of upwelling, winds blow across the sea surface at a particular direction, as a result of the wind, the water is transported a net of 90 degrees from the direction of the wind due to Coriolis forces and Ekman transport. This results in a spiral of water movement down the water column, then, it is the Coriolis forces that dictate which way the water will move, in the Northern hemisphere, the water is transported to the right of the direction of the wind. In the Southern Hemisphere, the water is transported to the left of the wind, if this net movement of water is divergent, then upwelling of deep water occurs to replace the water that was lost. The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world. Wind-driven currents are diverted to the right of the winds in the Northern Hemisphere, the result is a net movement of surface water at right angles to the direction of the wind, known as the Ekman transport. When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water. Normally, this process occurs at a rate of about 5–10 meters per day. Deep waters are rich in nutrients, including nitrate, phosphate and silicic acid, Upwelling regions therefore result in very high levels of primary production in comparison to other areas of the ocean. They account for about 50% of global marine productivity, high primary production propagates up the food chain because phytoplankton are at the base of the oceanic food chain. All of these currents support major fisheries, the four major eastern boundary currents in which coastal upwelling primarily occurs are the Canary Current, Benguela Current, California Current, and Humboldt Current. The Benguela Current is the boundary of the South Atlantic subtropical gyre. The subsystems are divided by an area of permanent upwelling off of Luderitz, the California Current System is an eastern boundary current of the North Pacific that is also characterized by a north and south split
9.
Indian Ocean
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The Indian Ocean is the third largest of the worlds oceanic divisions, covering 70,560,000 km2. It is bounded by Asia on the north, on the west by Africa, on the east by Australia, the Indian Ocean is known as Ratnākara, the mine of gems in ancient Sanskrit literature, and as Hind Mahāsāgar, in Hindi. The northernmost extent of the Indian Ocean is approximately 30° north in the Persian Gulf, the oceans continental shelves are narrow, averaging 200 kilometres in width. An exception is found off Australias western coast, where the width exceeds 1,000 kilometres. The average depth of the ocean is 3,890 m and its deepest point is Diamantina Deep in Diamantina Trench, at 8,047 m deep, Sunda Trench has a depth of 7, 258–7,725 m. North of 50° south latitude, 86% of the basin is covered by pelagic sediments. The remaining 14% is layered with terrigenous sediments, glacial outwash dominates the extreme southern latitudes. The major choke points include Bab el Mandeb, Strait of Hormuz, the Lombok Strait, the Strait of Malacca, the Indian Ocean is artificially connected to the Mediterranean Sea through the Suez Canal, which is accessible via the Red Sea. All of the Indian Ocean is in the Eastern Hemisphere and the centre of the Eastern Hemisphere is in this ocean, marginal seas, gulfs, bays and straits of the Indian Ocean include, The climate north of the equator is affected by a monsoon climate. Strong north-east winds blow from October until April, from May until October south, in the Arabian Sea the violent Monsoon brings rain to the Indian subcontinent. In the southern hemisphere, the winds are milder. When the monsoon winds change, cyclones sometimes strike the shores of the Arabian Sea, the Indian Ocean is the warmest ocean in the world. Long-term ocean temperature records show a rapid, continuous warming in the Indian Ocean, Indian Ocean warming is the largest among the tropical oceans, and about 3 times faster than the warming observed in the Pacific. Research indicates that human induced greenhouse warming, and changes in the frequency, among the few large rivers flowing into the Indian Ocean are the Zambezi, Shatt al-Arab, Indus, Godavari, Krishna, Narmada, Ganges, Brahmaputra, Jubba and Irrawaddy River. The oceans currents are controlled by the monsoon. Two large gyres, one in the northern hemisphere flowing clockwise and one south of the equator moving anticlockwise, during the winter monsoon, however, currents in the north are reversed. Deep water circulation is controlled primarily by inflows from the Atlantic Ocean, the Red Sea, north of 20° south latitude the minimum surface temperature is 22 °C, exceeding 28 °C to the east. Southward of 40° south latitude, temperatures drop quickly, surface water salinity ranges from 32 to 37 parts per 1000, the highest occurring in the Arabian Sea and in a belt between southern Africa and south-western Australia
10.
Agulhas Current
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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
11.
Cape of Good Hope
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The Cape of Good Hope is a rocky headland on the Atlantic coast of the Cape Peninsula, South Africa. In fact, the southernmost point of Africa is Cape Agulhas, when following the western side of the African coastline from the equator, however, the Cape of Good Hope marks the point where a ship begins to travel more eastward than southward. Thus, the first modern rounding of the cape in 1488 by Portuguese explorer Bartolomeu Dias was a milestone in the attempts by the Portuguese to establish trade relations with the Far East. Dias called the cape Cabo das Tormentas, which was the name of the Cape of Good Hope. As one of the capes of the South Atlantic Ocean. It is a waypoint on the Cape Route and the route followed by clipper ships to the Far East and Australia. The term Cape of Good Hope is also used in three ways, It is a section of the Table Mountain National Park, within which the cape of the same name, as well as Cape Point. Prior to its incorporation into the park, this section constituted the Cape Point Nature Reserve. It was the name of the early Cape Colony established by the Dutch in 1652, just before the Union of South Africa was formed, the term referred to the entire region that in 1910 was to become the Cape of Good Hope Province. When Eudoxus was returning from his voyage to India the wind forced him south of the Gulf of Aden. Somewhere along the coast of East Africa, he found the remains of the ship, due to its appearance and the story told by the natives, Eudoxus concluded that the ship was from Gades and had sailed anti-clockwise around Africa, passing the Cape and entering the Indian Ocean. This inspired him to repeat the voyage and attempt a circumnavigation of the continent, organising the expedition on his own account he set sail from Gades and began to work down the African coast. The difficulties were too great, however, and he was obliged to return to Europe, after this failure he again set out to circumnavigate Africa. Although some, such as Pliny, claimed that Eudoxus did achieve his goal, in the 1450 Fra Mauro map, the Indian Ocean is depicted as connected to the Atlantic. It sailed for 40 days in a south-westerly direction without ever finding anything other than wind and water. According to these people themselves, the ship went some 2,000 miles ahead until - once favourable conditions came to an end - it turned round and sailed back to Cape Diab in 70 days. The ships called junks that navigate these seas carry four masts or more, some of which can be raised or lowered, and have 40 to 60 cabins for the merchants and only one tiller. They can navigate without a compass, because they have an astrologer, thus one can believe and confirm what is said by both these and those, and that they had therefore sailed 4,000 miles
12.
Cape Agulhas
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Cape Agulhas is a rocky headland in Western Cape, South Africa. It is the southern tip of the African continent and the beginning of the dividing line between the Atlantic and Indian Oceans according to the International Hydrographic Organization. Historically, the cape has been known to sailors as a hazard on the traditional clipper route. It is sometimes regarded as one of the great capes and it was most commonly known in English as Cape LAgulhas until the 20th century. The town of LAgulhas is located near to the cape, Cape Agulhas is located in the Overberg region,170 kilometres southeast of Cape Town. The cape is within the Cape Agulhas Local Municipality in the Overberg District of the Western Cape province of South Africa, the nearby small airport of Andrews Field services Agulhas. South of Cape Agulhas the warm Agulhas Current that flows south along the east coast of Africa retroflects back into the Indian Ocean. While retroflecting, it pinches off large ocean eddies that drift into the South Atlantic Ocean and take enormous amounts of heat and this mechanism constitutes one of the key elements in the global conveyor belt circulation of heat and salt. Unlike its better-known relative, the Cape of Good Hope, Cape Agulhas is relatively unspectacular, a survey marker indicates the location of the cape, which would otherwise be difficult to identify. The waters of the Agulhas Bank off the coast are quite shallow and are renowned as one of the best fishing grounds in South Africa, the rocks that form Cape Agulhas belong to the Table Mountain Group, often loosely termed the Table Mountain sandstone. They are closely linked to the formations that are exposed in the spectacular cliffs of Table Mountain, Cape Point. The climate is mild, with no temperature or rainfall extremes. According to South African National Parks, who administer the nature reserve, over the past few hundred years it has been believed that around 150 ships have sunk around Agulhas. These conditions are caused by a number of factors and these hazards have combined to make the cape notorious among sailors. The coast here is littered with wrecks, Arniston, Cooranga, Elise, Federal Lakes, Geortyrder, Gouritz, owing to the hazards and following the loss of several vessels, notably the Arniston, a lighthouse was built in 1848. The lighthouse now plays host to a museum and a rustic restaurant. Cape Agulhas Local Municipality, the municipality containing Cape Agulhas, Agulhas National Park Cape of Good Hope, near Cape Town, often incorrectly regarded as the southernmost point of Africa. SS Wafra oil spill Cape Agulhas Lighthouse Agulhas National Park
13.
Ekman transport
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Ekman transport, part of Ekman motion theory first investigated in 1902 by Vagn Walfrid Ekman, is the term given for the 90° net transport of the surface layer of a fluid by wind forcing. This phenomenon was first noted by Fridtjof Nansen, who recorded that ice transport appeared to occur at an angle to the wind direction during his Arctic expedition during the 1890s. Ekman theory explains the state of circulation if water currents were driven only by the transfer of momentum from the wind. In the physical world, this is difficult to observe because of the influences of many simultaneous current driving forces, though the following theory technically applies to the idealized situation involving only wind forces, Ekman motion describes the wind-driven portion of circulation seen in the surface layer. Surface currents flow at a 45° angle to the due to a balance between the Coriolis force and the drags generated by the wind and the water. If the ocean is divided vertically into thin layers, the magnitude of the velocity decreases from a maximum at the surface until it dissipates, the direction also shifts slightly across each subsequent layer. This is called the Ekman spiral, the layer of water from the surface to the point of dissipation of this spiral is known as the Ekman layer. If all flow over the Ekman layer is integrated, the net transportation is at 90° to the right of the wind in the northern hemisphere. Some assumptions of the dynamics involved in the process must be made in order to simplify the process to a point where it is solvable. Here M x and M y represent the zonal and meridional mass transport terms with units of mass per time per unit length. Contrarily to common logic, north-south winds cause mass transport in the East-West direction, in order to understand the vertical velocity structure of the water column, equations 1 and 2 can be rewritten in terms of the vertical eddy viscosity term. ∂ τ x ∂ z = ρ A z ∂2 u ∂ z 2, ∂ τ y ∂ z = ρ A z ∂2 v ∂ z 2, where A z is the vertical eddy viscosity coefficient. This gives a set of equations of the form A z ∂2 u ∂ z 2 = − f v, A z ∂2 v ∂ z 2 = f u. In order to solve this system of two equations, two boundary conditions can be applied, →0 as z → ∞, friction is equal to wind stress at the free surface. Things can be simplified by considering wind blowing in the y-direction only. By solving this at z=0, the current is found to be 45 degrees to the right of the wind in the Northern Hemisphere. This also gives the shape of the Ekman spiral, both in magnitude and direction. Integrating these equations over the Ekman layer shows that the net Ekman transport term is 90 degrees to the right of the wind in the Northern Hemisphere
14.
Euphotic zone
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The photic zone, euphotic zone, or sunlight or zone is the depth of the water in a lake or ocean that is exposed to such intensity of sunlight which designates compensation point, i. e. It extends from the surface down to a depth where light intensity falls to one percent of that at the surface, accordingly, its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes and it also varies with seasonal changes in turbidity. About 90% of all marine life lives in the photic zone, a small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges. The zone which extends from the base of the zone to about 200 metres is sometimes called the disphotic zone. While there is light, it is insufficient for photosynthesis. The euphotic zone together with the disphotic zone coincides with the epipelagic zone, the bottommost zone, below the euphotic zone, is called the aphotic zone. Most deep ocean waters belong to this zone, the transparency of the water, which determines the depth of the photic zone, is measured simply with a Secchi disk. It may also be measured with a photometer lowered into the water, electromagnetic absorption by water Epipelagic fish
15.
Phytoplankton
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Phytoplankton /ˌfaɪtoʊˈplæŋktən/ are the autotrophic components of the plankton community and a key part of oceans, seas and freshwater basin ecosystems. The name comes from the Greek words φυτόν, meaning plant, most phytoplankton are too small to be individually seen with the unaided eye. Phytoplankton are photosynthesizing microscopic organisms that inhabit the upper layer of almost all oceans. They are agents for primary production, the creation of organic compounds from carbon dioxide dissolved in the water, Phytoplankton obtain energy through the process of photosynthesis and must therefore live in the well-lit surface layer of an ocean, sea, lake, or other body of water. Phytoplankton account for half of all activity on Earth. Their cumulative energy fixation in carbon compounds is the basis for the vast majority of oceanic, the effects of anthropogenic warming on the global population of phytoplankton is an area of active research. Additionally, changes in the mortality of phytoplankton due to rates of zooplankton grazing may be significant, as a side note, one of the more remarkable food chains in the ocean – remarkable because of the small number of links – is that of phytoplankton-feeding krill feeding baleen whales. Phytoplankton are also dependent on minerals. However, across large regions of the World Ocean such as the Southern Ocean and this has led to some scientists advocating iron fertilization as a means to counteract the accumulation of human-produced carbon dioxide in the atmosphere. Large-scale experiments have added iron to the oceans to promote phytoplankton growth, however, controversy about manipulating the ecosystem and the efficiency of iron fertilization has slowed such experiments. Phytoplankton depend on other substances to survive as well, in particular, Vitamin B is crucial. Areas in the ocean have been identified as having a lack of Vitamin B. While almost all species are obligate photoautotrophs, there are some that are mixotrophic and other. Of these, the best known are dinoflagellate genera such as Noctiluca and Dinophysis, the term phytoplankton encompasses all photoautotrophic microorganisms in aquatic food webs. Phytoplankton serve as the base of the food web, providing an essential ecological function for all aquatic life. However, unlike terrestrial communities, where most autotrophs are plants, phytoplankton are a group, incorporating protistan eukaryotes. There are about 5,000 known species of marine phytoplankton, how such diversity evolved despite scarce resources is unclear. In terms of numbers, the most important groups of phytoplankton include the diatoms, cyanobacteria and dinoflagellates, one group, the coccolithophorids, is responsible for the release of significant amounts of dimethyl sulfide into the atmosphere
16.
Zooplankton
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Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word zooplankton is derived from the Greek zoon, meaning animal, individual zooplankton are usually microscopic, but some are larger and visible with the naked eye. Zooplankton is a categorization spanning a range of organism sizes including small protozoans, although zooplankton are primarily transported by ambient water currents, many have locomotion, used to avoid predators or to increase prey encounter rate. Ecologically important protozoan zooplankton groups include the foraminiferans, radiolarians and dinoflagellates and this wide phylogenetic range includes a similarly wide range in feeding behavior, filter feeding, predation and symbiosis with autotrophic phytoplankton as seen in corals. Zooplankton feed on bacterioplankton, phytoplankton, other zooplankton, detritus, as a result, zooplankton are primarily found in surface waters where food resources are abundant. Just as any species can be limited within a geographical region, however, species of zooplankton are not dispersed uniformly or randomly within a region of the ocean. As with phytoplankton, ‘patches’ of zooplankton species exist throughout the ocean, zooplankton patchiness can also be influenced by biological factors, as well as other physical factors. Biological factors include breeding, predation, concentration of phytoplankton, the physical factor that influences zooplankton distribution the most is mixing of the water column that affects nutrient availability and, in turn, phytoplankton production. Since they are small, zooplankton can respond rapidly to increases in phytoplankton abundance, for instance. Zooplankton can also act as a disease reservoir, crustacean zooplankton have been found to house the bacterium Vibrio cholerae, which causes cholera, by allowing the cholera vibrios to attach to their chitinous exoskeletons. This symbiotic relationship enhances the ability to survive in an aquatic environment, as the exoskeleton provides the bacterium with carbon. A global coverage database of zooplankton biomass and abundance data
17.
Oxygen minimum zone
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The Oxygen minimum zone, sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,000 meters, surface ocean waters generally have oxygen concentrations close to equilibrium with the Earths atmosphere. In general, colder waters hold more oxygen than warmer waters, as water moves out of the mixed layer into the thermocline it is exposed to a rain of organic matter from above. Aerobic bacteria feed on organic matter, oxygen is used as part of the bacterial metabolic process lowering its concentration within the water. Therefore, the concentration of oxygen in water is dependent on the amount of oxygen it had when it was at the surface minus depletion by deep sea organisms. The downward flux of matter decreases sharply with depth, with 80-90% being consumed in the top 1000m. The deep ocean thus has higher oxygen because rates of consumption are low compared with the supply of cold. In the surface layers, oxygen is supplied by exchange with the atmosphere, depths in between, however, have higher rates of oxygen consumption and lower rates of advective supply of oxygen-rich waters. For example, wind blowing parallel to the coast causes Ekman Transport that upwells nutrients from deep water, the increased nutrients support phytoplankton blooms, zooplankton grazing, and an overall productive food web at the surface. The byproducts of these blooms and the subsequent grazing sink in the form of particulate and this “rain” of organic matter feeds the Microbial Loop and may lead to bacterial blooms in water below the euphotic zone due to the influx of nutrients. Physical processes then constrain the mixing and isolate this low oxygen water from outside water, vertical mixing is constrained due to the separation from the mixed layer by depth. Horizontal mixing is constrained by bathymetry and boundaries formed by interactions with sub-tropical gyres, despite the low oxygen conditions, organisms have evolved to live in and around OMZs. For those organisms, like the vampire squid, special adaptations are needed to make do with lesser amounts of oxygen or to extract oxygen from the water more efficiently. For example, the Giant Red Mysid continues to live aerobically in OMZs, another strategy used by some classes of bacteria in the oxygen minimum zones is to use nitrate rather than oxygen, thus drawing down the concentrations of this important nutrient. The oxygen minimum zones thus play an important role in regulating the productivity, hypoxia for a number of articles related to environmental oxygen depletion Dead zone, localized areas of dramatically reduced oxygen levels, often due to human impacts
18.
Pilchard
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Sardine and pilchard are common names used to refer to various small, oily fish within the herring family of Clupeidae. The term sardine was first used in English during the early 15th century and may come from the Mediterranean island of Sardinia, the terms sardine and pilchard are not precise, and what is meant depends on the region. The United Kingdoms Sea Fish Industry Authority, for example, classifies sardines as young pilchards, one criterion suggests fish shorter in length than 15 cm are sardines, and larger fish are pilchards. Typically, sardines are caught with encircling nets, particularly purse seines, many modifications of encircling nets are used, including traps or weirs. The latter are stationary enclosures composed of stakes into which schools of sardines are diverted as they swim along the coast, the fish are caught mainly at night, when they approach the surface to feed on plankton. After harvesting, the fish are submerged in brine while they are transported to shore, sardines are commercially fished for a variety of uses, for bait, for immediate consumption, for drying, salting, or smoking, and for reduction into fish meal or oil. The chief use of sardines is for consumption, but fish meal is used as animal feed, while sardine oil has many uses, including the manufacture of paint, varnish. Sardines are commonly consumed by human beings, fresh sardines are often grilled, pickled or smoked, or preserved in cans. Sardines are rich in vitamins and minerals, a small serving of sardines once a day can provide 13 percent of vitamin B2, roughly one-quarter of niacin, and about 150 percent of the recommended daily value of vitamin B12. All B vitamins help to support proper nervous system function and are used for energy metabolism, also, sardines are high in the major minerals such as phosphorus, calcium, potassium, and some trace minerals including iron and selenium. Sardines are also a source of marine omega-3 fatty acids. Recent studies suggest that consumption of omega-3 fatty acids reduces the likelihood of developing Alzheimers disease. These fatty acids can also lower blood sugar levels and they are also a good source of vitamin D, calcium, vitamin B12, and protein. Because they are low in the chain, sardines are very low in contaminants such as mercury. Pilchard fishing and processing became an industry in Cornwall from around 1750 to around 1880. Catches varied from year to year and, in 1871 the catch was 47,000 hogsheads while in 1877 only 9,477 hogsheads, a hogshead contained 2,300 to 4,000 pilchards and, when filled with pressed pilchards, weighed 476 lbs. The pilchards were exported to Roman Catholic countries such as Italy. The chief market for the oil was Bristol where it is used on machinery, as of 2007, however, stocks are improving
19.
Anchovy
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An anchovy is a small, common salt-water forage fish of the family Engraulidae. The 144 species are placed in 17 genera, they are found in the Atlantic, Indian, and Pacific Oceans, and in the Black Sea, Anchovies are usually classified as oily fish. Anchovies are small, green fish with blue reflections due to a longitudinal stripe that runs from the base of the caudal fin. They range from 2 to 40 cm in length. The snout is blunt with tiny, sharp teeth in both jaws, the snout contains a unique rostral organ, believed to be sensory in nature, although its exact function is unknown. The mouth is larger than that of herrings and silversides, two fish which anchovies closely resemble in other respects, the anchovy eats plankton and recently hatched fish. Anchovies are found in scattered areas throughout the oceans, but are concentrated in temperate waters. They are generally accepting of a wide range of temperatures. Large schools can be found in shallow, brackish areas with muddy bottoms, as in estuaries and they are abundant in the Mediterranean, particularly in the Alboran Sea, Aegean Sea and the Black Sea. The species is caught along the coasts of Crete, Greece, Sicily, Italy, France, Turkey. They are also found on the coast of northern Africa, the range of the species also extends along the Atlantic coast of Europe to the south of Norway. Spawning occurs between October and March, but not in water colder than 12 °C, the anchovy appears to spawn at least 100 km from the shore, near the surface of the water. The anchovy is a significant food source for almost every predatory fish in its environment, including the California halibut, rock fish, yellowtail, shark, chinook, and coho salmon. It is also important to marine mammals and birds, for example, breeding success of California brown pelicans. Anchovies, like most clupeoids, are filter-feeders that open their mouths as they swim, as water passes through the mouth and out the gills, food particles are sieved by gill rakers and transferred into the esophagus. * Type species On average, the Turkish commercial fishing fleet catches around 300,000 tons per year, the largest catch is in November and December. The Peruvian anchovy fishery is one of the largest in the world, in 1973 it collapsed catastrophically due to the combined effects of overfishing and El Niño and did not recover fully for two decades. A traditional method of processing and preserving anchovies is to gut and salt them in brine, allow them to mature and this results in a characteristic strong flavor and the flesh turns deep grey
20.
Namibia
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Namibia, officially the Republic of Namibia, is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south, although it does not border Zimbabwe, a part of less than 200 metres of the Zambezi River separates the two countries. Namibia gained independence from South Africa on 21 March 1990, following the Namibian War of Independence. Its capital and largest city is Windhoek, and it is a state of the United Nations, the Southern African Development Community, the African Union. The dry lands of Namibia were inhabited since early times by the San, Damara, since about the 14th century, immigrating Bantu peoples arrived as part of the Bantu expansion. Since then the Bantu groups in total, known as the Ovambo people, have dominated the population of the country, in the late 19th century during European colonization, the German Empire established rule over most of the territory as a protectorate in 1884. It began to develop infrastructure and farming, and maintained this German colony until 1915, after the end of World War I, in 1920 the League of Nations mandated the country to the United Kingdom, under administration by South Africa. It imposed its laws, including racial classifications and rules, from 1948, with the National Party elected to power, South Africa applied apartheid also to what was known as South West Africa. In 1878 the Cape of Good Hope had annexed the port of Walvis Bay and the offshore Penguin Islands, following continued guerrilla warfare, South Africa installed an interim administration in Namibia in 1985. Namibia obtained full independence from South Africa in 1990, but Walvis Bay and the Penguin Islands remained under South African control until 1994. Namibia has a population of 2.1 million people and a stable multi-party parliamentary democracy, Agriculture, herding, tourism and the mining industry – including mining for gem diamonds, uranium, gold, silver, and base metals – form the basis of its economy. The large, arid Namib Desert has resulted in Namibia being overall one of the least densely populated countries in the world, Namibia enjoys high political, economic and social stability. The name of the country is derived from the Namib Desert, before its independence in 1990, the area was known first as German South-West Africa, then as South-West Africa, reflecting the colonial occupation by the Germans and the South Africans. The dry lands of Namibia were inhabited since early times by San, Damara, from about the 14th century, immigrating Bantu peoples arrived during the Bantu expansion from central Africa. From the late 18th century onwards, Oorlam people from Cape Colony crossed the Orange River and their encounters with the nomadic Nama tribes were largely peaceful. The missionaries accompanying the Oorlam were well received by them, the right to use waterholes, on their way further northwards, however, the Oorlam encountered clans of the Herero at Windhoek, Gobabis, and Okahandja, who resisted their encroachment. The Nama-Herero War broke out in 1880, with hostilities ebbing only after the German Empire deployed troops to the places and cemented the status quo among the Nama, Oorlam. The first Europeans to disembark and explore the region were the Portuguese navigators Diogo Cão in 1485 and Bartolomeu Dias in 1486, like most of interior Sub-Saharan Africa, Namibia was not extensively explored by Europeans until the 19th century
21.
Cape Peninsula
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The Cape Peninsula is a generally rocky peninsula that juts out into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape of Good Hope, on the northern end is Table Mountain, overlooking Cape Town, South Africa. The peninsula is 52 km long from Mouille point in the north to Cape Point in the south. The Peninsula has been an island on and off for the past 5 million years, as sea levels fell and rose with the ice age and interglacial global warming cycles of, particularly, the Pleistocene. The last time that the Peninsula was an island was about 1.5 million years ago, soon afterwards it was joined to the mainland by the emergence from the sea of the sandy area now known as the Cape Flats. The towns and villages of the Cape Peninsula and Cape Flats now form part of the City of Cape Town Metropolitan Municipality, the Cape of Good Hope is sometimes given as the meeting point of the Atlantic and Indian Oceans. Thus the west coast of the Peninsula is invariably referred to as the Atlantic Coast and it is at Cape Point that the ocean to the south is often said to be divided into the Atlantic Ocean to the west, and the Indian Ocean to the east. However, according to the International Hydrographic Organization agreement that defines the ocean boundaries, from there it is retroflexed in an easterly direction by the South Atlantic, South Indian and Southern Ocean currents, known as the West Wind Drift, which flow eastwards round Antarctica. The Benguela Current, on the hand, is an upwelling current which brings cold. Having reached the surface it flows northwards as a result of the prevailing wind, thus the Benguela and Agulhas currents do not strictly meet anywhere, although eddies from the Agulhas current do from time to time round the Cape to join the Benguela Current. The park comprises a part of the undeveloped area of the Cape Peninsula. The coastal waters surrounding the Cape Peninsula are proclaimed as a protected area since 2004, and include several no-take zones. The waters of this protected area are unusual in that they are parts of two fairly distinct marine bioregions, namely the Agulhas Bioregion and the South-western Cape Bioregion. The boundary is at Cape Point, the Cape Peninsula has an unusually rich biodiversity. Its vegetation consists predominantly of several different types of the unique, on the sandy Cape Flats lowlands there are a few pockets of protected Cape Flats Sand Fynbos. The Peninsulas vegetation types form part of the Cape Floral Region protected areas, many of these species, including a great many types of proteas, are endemic to these mountains and can be found nowhere else. It is a showy orchid that blooms from January to March on the Table Mountain Sandstone regions of the mountain. Although they are widespread on the Back Table, the best place to view these beautiful blooms is in the Aqueduct off the Smuts Track
22.
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
23.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
24.
East Greenland Current
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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
25.
Transpolar Drift Stream
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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
26.
Brazil Current
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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
27.
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
28.
Caribbean Current
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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
29.
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
30.
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
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Loop Current
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Serving as the dominant circulation feature in the Eastern Gulf of Mexico, the Loop Currents transports between 23 and 27 sverdrups and reaches maximum flow speeds of from 1.5 to 1.8 meters/second. A related feature is an area of water with an eddy or Loop Current ring that separates from the Loop Current. Swirling at 1.8 to 2 meters/second, these rings drift to the west at speeds of 2 to 5 kilometers/day and have a lifespan of up to a year before they bump into the coast of Texas or Mexico. These eddies are composed of warm Caribbean waters and possess physical properties that isolate the masses from surrounding Gulf Common Waters, the rings can measure 200 to 400 kilometers in diameter and extend down to a depth of 1000 meters. Around 1970, it was believed that the Loop Current exhibited an annual cycle in which the Loop feature extended farther to the north during the summer, the Loop Current and its eddies may be detected by measuring sea surface level. Sea surface level of both the eddies and the Loop on September 21,2005 was up to 60 cm higher than surrounding water, on that day, Hurricane Rita passed over the Loop current and intensified into a Category 5 storm with the help of the warm water. In the Gulf of Mexico, the deepest areas of water are associated with the Loop Current. The warm waters of the Loop Current and its associated eddies provide more energy to hurricanes, as hurricanes pass over warm areas of the Gulf of Mexico, they convert the ocean’s heat into storm energy. As this energy is removed from the seas, a wake of colder water can be detected along the hurricane’s path and this is because heat is withdrawn from the ocean mixed layer in a number of ways. For instance, sensible and latent heat are lost directly to the cyclone across the air-sea interface. Also, the divergence of wind-driven mixed layer currents results in the upwelling of colder thermocline water. Finally, the turbulent entrainment of colder thermocline waters caused by wind stirring also results in the cooling of the surface waters and these are the reasons that the depth of the ocean mixed layer is more important in hurricane deepening than sea surface temperature. A thin veneer of surface waters will be more susceptible to hurricane induced cooling than waters with a larger mixed layer and deeper thermocline. Camille formed in the warm waters of the Caribbean, which enabled it to rapidly intensify into a category 3 hurricane in one day. It rounded the tip of Cuba, and its path took it directly over the Loop Current, all the way north towards the coast. Camille became a category 5 hurricane, with an intensity rarely seen, in 1980, Hurricane Allen strengthened to a category 5 hurricane while moving over the Loop Current, but it weakened before landfall in Texas. In 2005, Hurricane Katrina and Hurricane Rita both greatly increased in strength when they passed over the waters of the Loop Current. While not as infamous as Katrina, Hurricane Opal most definitively illustrates the abilities of a warm core ring
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North Atlantic Current
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The North Atlantic Current, also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current that extends the Gulf Stream north-eastward. The NAC originates from where the Gulf Stream turns north at the Southeast Newfoundland Rise, the NAC flows northward east of the Grand Banks, from 40°N to 51°N, before turning sharply east to cross the Atlantic. It transports more warm water to northern latitudes than any other boundary current. It reaches speeds of 2 knots near the North American coast, directed by topography, the NAC meanders heavily but, in contrast to the meanders of the Gulf Stream, the NAC meanders remain stable without breaking off into eddies. The colder parts of the Gulf Stream turn northward near the tail of the Grand Banks at 50°W where the Azores Current branches off to flow south of the Azores, from there the NAC flow north-eastward east of the Flemish Cap. Approaching the Mid-Atlantic Ridge, it turns eastward and becomes much broader. It then splits into a colder, north-eastern branch and an eastern branch. West of Continental Europe, it splits into two major branches, one branch goes southeast, later to become the Canary Current as it passes northwest Africa and turns southwest. The other major branch continues north along the coast of Northwestern Europe, other branches include the Irminger Current and the Norwegian Current. The North Atlantic Current, together with the Gulf Stream, have a reputation for having a considerable warming influence on European climate. The principal cause for differences in climate between North America and Europe is, however, winds rather than ocean currents. North Atlantic Oscillation Ocean gyre Physical oceanography Notes Sources The North Atlantic Current, elizabeth Rowe, Arthur J. Mariano, Edward H. Ryan, The Cooperative Institute for Marine and Atmospheric Studies
