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70-528: The EGC is composed of a mixture of three distinct water masses . The water masses are Polar Water, Atlantic Water, and Deep Water. These water masses can be clearly seen throughout the EGC's tract southward, however, the upper layer water masses do change some due to atmospheric interaction along with inflow from other water sources in the Nordic Seas. The top 150 meters of the EGC is considered polar water and it

140-421: A T-S diagram. In the diagram pictured at the top, it categorises a water mass by the temperature and salinity of the water and is represented by a single point. However, water masses are not constant. Throughout time climates can change, seasons can drag out, or there could be less rainfall meaning that the water masses might change in temperature or salinity. To have a complete water mass classification, it requires

210-427: A acertar: mas partiam os nossos mareantes muy ensinados e prouidos de estromentos e regras de astrologia e geometria que sam as cousas que os cosmographos ham dadar apercebidas (...) e leuaua cartas muy particularmente rumadas e na ja as de que os antigos vsauam" (were not done by chance: but our seafarers departed well taught and provided with instruments and rules of astrology (astronomy) and geometry which were matters

280-408: A minimum from January to March. This interannual variability occurs because during the summer months the sea ice melts back quite a bit, and it results in a lot of drifting sea ice that can be easily exported through Fram Strait during the windy times of October through December. During the winter months, the sea ice refreezes together and thus the ability to have numerous sea ice drifts decreases due to

350-563: A paper on reefs and the formation of atolls as a result of the second voyage of HMS Beagle in 1831–1836. Robert FitzRoy published a four-volume report of Beagle ' s three voyages. In 1841–1842 Edward Forbes undertook dredging in the Aegean Sea that founded marine ecology. The first superintendent of the United States Naval Observatory (1842–1861), Matthew Fontaine Maury devoted his time to

420-525: A profound impact on the wind field over the Arctic. During high NAO/AO indexes the cyclonic wind field over the Arctic becomes very strong, this transports more ice out through Fram Strait and into the EGC. During low NAO/AO indexes the cyclonic wind field is quite small and thus the transport out of the Fram Strait diminishes greatly. Current research in the EGC is largely focused on freshwater fluxes (in

490-625: A voyage around the Cape of Good Hope in 1777, he mapped "the banks and currents at the Lagullas " . He was also the first to understand the nature of the intermittent current near the Isles of Scilly , (now known as Rennell's Current). The tides and currents of the ocean are distinct. Tides are the rise and fall of sea levels created by the combination of the gravitational forces of the Moon along with

560-424: A wide range of disciplines to deepen their understanding of the world’s oceans, incorporating insights from astronomy , biology , chemistry , geography , geology , hydrology , meteorology and physics . Humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations on tides were recorded by Aristotle and Strabo in 384–322 BC. Early exploration of

630-621: 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 temperatures are relatively constant. This level typically extends from 1000 meters to the bottom of the ocean. The temperatures in this bottom level are normally below 0 °C and

700-465: Is also identified by its non-conservative flow tracers such as silicate, nitrate, oxygen, and phosphate. Water masses are generally distinguished not only by their respective tracers but also by their location in the Worlds' oceans. Water masses are also distinguished by their vertical position so that there are surface water masses, intermediate water masses and deep water masses. Common water masses in

770-528: 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 (e.g. freezing point of low-salinity sea water), and the salinity varies greatly from 30 psu (near

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840-588: Is due to the change in the regime of winds and currents: the North Atlantic gyre and the Equatorial counter current will push south along the northwest bulge of Africa, while the uncertain winds where the Northeast trades meet the Southeast trades (the doldrums) leave a sailing ship to the mercy of the currents. Together, prevalent current and wind make northwards progress very difficult or impossible. It

910-717: Is likely to affect marine organisms with calcareous shells, such as oysters, clams, sea urchins and corals, and the carbonate compensation depth will rise closer to the sea surface. Affected planktonic organisms will include pteropods , coccolithophorids and foraminifera , all important in the food chain . In tropical regions, corals are likely to be severely affected as they become less able to build their calcium carbonate skeletons, in turn adversely impacting other reef dwellers. The current rate of ocean chemistry change seems to be unprecedented in Earth's geological history, making it unclear how well marine ecosystems will adapt to

980-549: Is remembered in the navigation context for the determination of the loxodromic curve: the shortest course between two points on the surface of a sphere represented onto a two-dimensional map. When he published his "Treatise of the Sphere" (1537), mostly a commentated translation of earlier work by others, he included a treatise on geometrical and astronomic methods of navigation. There he states clearly that Portuguese navigations were not an adventurous endeavour: "nam se fezeram indo

1050-444: Is the scientific study of the ocean , including its physics , chemistry , biology , and geology . It is an Earth science , which covers a wide range of topics, including ocean currents , waves , and geophysical fluid dynamics ; fluxes of various chemical substances and physical properties within the ocean and across its boundaries; ecosystem dynamics; and plate tectonics and seabed geology. Oceanographers draw upon

1120-705: The Challenger expedition . Challenger , leased from the Royal Navy, was modified for scientific work and equipped with separate laboratories for natural history and chemistry . Under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical miles (130,000 km) surveying and exploring. On her journey circumnavigating the globe, 492 deep sea soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature observations were taken. Around 4,700 new species of marine life were discovered. The result

1190-779: The Ishiguro Storm Surge Computer ) generally now replaced by numerical methods (e.g. SLOSH .) An oceanographic buoy array was established in the Pacific to allow prediction of El Niño events. 1990 saw the start of the World Ocean Circulation Experiment (WOCE) which continued until 2002. Geosat seafloor mapping data became available in 1995. Study of the oceans is critical to understanding shifts in Earth's energy balance along with related global and regional changes in climate ,

1260-1169: The Mediterranean Science Commission . Marine research institutes were already in existence, starting with the Stazione Zoologica Anton Dohrn in Naples, Italy (1872), the Biological Station of Roscoff, France (1876), the Arago Laboratory in Banyuls-sur-mer, France (1882), the Laboratory of the Marine Biological Association in Plymouth, UK (1884), the Norwegian Institute for Marine Research in Bergen, Norway (1900),

1330-560: The biosphere and biogeochemistry . The atmosphere and ocean are linked because of evaporation and precipitation as well as thermal flux (and solar insolation ). Recent studies have advanced knowledge on ocean acidification , ocean heat content , ocean currents , sea level rise , the oceanic carbon cycle , the water cycle , Arctic sea ice decline , coral bleaching , marine heatwaves , extreme weather , coastal erosion and many other phenomena in regards to ongoing climate change and climate feedbacks . In general, understanding

1400-481: The 29 days Cabral took from Cape Verde up to landing in Monte Pascoal , Brazil. The Danish expedition to Arabia 1761–67 can be said to be the world's first oceanographic expedition, as the ship Grønland had on board a group of scientists, including naturalist Peter Forsskål , who was assigned an explicit task by the king, Frederik V , to study and describe the marine life in the open sea, including finding

1470-655: The Azores), bringing what is now Brazil into the Portuguese area of domination. The knowledge gathered from open sea exploration allowed for the well-documented extended periods of sail without sight of land, not by accident but as pre-determined planned route; for example, 30 days for Bartolomeu Dias culminating on Mossel Bay , the three months Gama spent in the South Atlantic to use the Brazil current (southward), or

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1540-538: The EGC comes from two different sources. The first source of Atlantic Water originates from westward directed Atlantic water in the West Spitsbergen Current . This current sends Atlantic water (AW) into the Fram Strait , and because it is more dense than 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. This

1610-455: The EGC, these specific sources do not penetrate very well into the central Greenland Sea where the deep convection takes place. They then decide that there must be some other freshwater influence in the central Greenland Sea. They believe it may be from solid sea ice being transported to the central Greenland Sea and then melting. Solid sea ice is very mobile, and winds can easily direct its flow along with ocean currents. Previous thoughts were that

1680-472: 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 quite strong with annual averages of 6–12 cm/s in the upper part of the EGC (<500 m) with inter-annual maximums of 20–30 cm/s. It was estimated in 1991 by Hopkins et al. that

1750-656: The Gulf Stream's cause. Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769–1770. Information on the currents of the Pacific Ocean was gathered by explorers of the late 18th century, including James Cook and Louis Antoine de Bougainville . James Rennell wrote the first scientific textbooks on oceanography, detailing the current flows of the Atlantic and Indian oceans. During

1820-857: The Laboratory für internationale Meeresforschung, Kiel, Germany (1902). On the other side of the Atlantic, the Scripps Institution of Oceanography was founded in 1903, followed by the Woods Hole Oceanographic Institution in 1930, the Virginia Institute of Marine Science in 1938, the Lamont–Doherty Earth Observatory at Columbia University in 1949, and later the School of Oceanography at University of Washington . In Australia ,

1890-655: The North Atlantic Ocean. It is a major pathway for sea ice to leave the Arctic. It is estimated that more than 90% of the Arctic Sea Ice exported from the Arctic takes place within the East Greenland Current. The volume of ice exported on an annual scale is a strong function of multiple atmospheric variables (wind, temperature, etc.) and oceanic variables and dynamics. There is a maximum of ice-flux export from October through December and

1960-561: The Sun (the Sun just in a much lesser extent) and are also caused by the Earth and Moon orbiting each other. An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect , breaking waves , cabbeling , and temperature and salinity differences . Sir James Clark Ross took the first modern sounding in deep sea in 1840, and Charles Darwin published

2030-552: The cause of mareel , or milky seas. For this purpose, the expedition was equipped with nets and scrapers, specifically designed to collect samples from the open waters and the bottom at great depth. Although Juan Ponce de León in 1513 first identified the Gulf Stream , and the current was well known to mariners, Benjamin Franklin made the first scientific study of it and gave it its name. Franklin measured water temperatures during several Atlantic crossings and correctly explained

2100-641: The centre for oceanographic research well into the 20th century. Murray was the first to study marine trenches and in particular the Mid-Atlantic Ridge , and map the sedimentary deposits in the oceans. He tried to map out the world's ocean currents based on salinity and temperature observations, and was the first to correctly understand the nature of coral reef development. In the late 19th century, other Western nations also sent out scientific expeditions (as did private individuals and institutions). The first purpose-built oceanographic ship, Albatros ,

2170-460: The context of the physical, chemical and geological characteristics of their ocean environment. Chemical oceanography is the study of the chemistry of the ocean. Whereas chemical oceanography is primarily occupied with the study and understanding of seawater properties and its changes, ocean chemistry focuses primarily on the geochemical cycles . The following is a central topic investigated by chemical oceanography. Ocean acidification describes

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2240-511: The cosmographers would provide (...) and they took charts with exact routes and no longer those used by the ancient). His credibility rests on being personally involved in the instruction of pilots and senior seafarers from 1527 onwards by Royal appointment, along with his recognized competence as mathematician and astronomer. The main problem in navigating back from the south of the Canary Islands (or south of Boujdour ) by sail alone,

2310-542: The currents and winds of the Atlantic, is demonstrated by the understanding of the seasonal variations, with expeditions setting sail at different times of the year taking different routes to take account of seasonal predominate winds. This happens from as early as late 15th century and early 16th: Bartolomeu Dias followed the African coast on his way south in August 1487, while Vasco da Gama would take an open sea route from

2380-456: The decade long period between Bartolomeu Dias finding the southern tip of Africa, and Gama's departure; additionally, there are indications of further travels by Bartolomeu Dias in the area. The most significant consequence of this systematic knowledge was the negotiation of the Treaty of Tordesillas in 1494, moving the line of demarcation 270 leagues to the west (from 100 to 370 leagues west of

2450-406: The decrease in ocean pH that is caused by anthropogenic carbon dioxide (CO 2 ) emissions into the atmosphere . Seawater is slightly alkaline and had a preindustrial pH of about 8.2. More recently, anthropogenic activities have steadily increased the carbon dioxide content of the atmosphere; about 30–40% of the added CO 2 is absorbed by the oceans, forming carbonic acid and lowering

2520-469: The deep water formation in the Nordic Seas. Jones et al. note that there are three different freshwater sources for the EGC: Pacific water, river runoff, and sea-ice meltwater. They find that the biggest contributor to the freshening of the EGC is due to river runoff, followed by Pacific water, and a distant last is sea-ice meltwater (nearly negligible). They find that even though these sources freshen

2590-567: The extra heat stored in the ocean from changes in Earth's energy balance . The increase in the ocean heat play an important role in sea level rise , because of thermal expansion . Ocean warming accounts for 90% of the energy accumulation associated with global warming since 1971. Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable

2660-433: The first all-woman oceanographic expedition. Until that time, gender policies restricted women oceanographers from participating in voyages to a significant extent. From the 1970s, there has been much emphasis on the application of large scale computers to oceanography to allow numerical predictions of ocean conditions and as a part of overall environmental change prediction. Early techniques included analog computers (such as

2730-485: The first woman to have earned a PhD (at Scripps) in the United States, completed a major work on diatoms that remained the standard taxonomy in the field until well after her death in 1999. In 1940, Cupp was let go from her position at Scripps. Sverdrup specifically commended Cupp as a conscientious and industrious worker and commented that his decision was no reflection on her ability as a scientist. Sverdrup used

2800-400: The ice less dense than the water which is why glaciers float. This also in turn causes the salinity of the water to decrease. The salinity of the water makes water freeze at lower temperatures than freshwater. Freshwater freezes at the standard 0 °C (32 °F), while saltwater freezes at an average of -2 °C (28.4 °F). The best method of classifying a water mass is through using

2870-403: The increase in overall sea ice extent. Essentially open water drifting decreases substantially during the winter months. The volume export ranges greatly from year to year. It can be as high as 5000 km/year and as low as 1000 km/year. Atmospheric forcings also have a strong impact on Arctic Sea Ice export through the EGC. The North Atlantic Oscillation (NAO)/Arctic Oscillation (AO) has

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2940-400: The instructor billet vacated by Cupp to employ Marston Sargent, a biologist studying marine algae, which was not a new research program at Scripps. Financial pressures did not prevent Sverdrup from retaining the services of two other young post-doctoral students, Walter Munk and Roger Revelle . Cupp's partner, Dorothy Rosenbury, found her a position teaching high school, where she remained for

3010-537: The latitude of Sierra Leone , spending three months in the open sea of the South Atlantic to profit from the southwards deflection of the southwesterly on the Brazilian side (and the Brazilian current going southward - Gama departed in July 1497); and Pedro Álvares Cabral (departing March 1500) took an even larger arch to the west, from the latitude of Cape Verde, thus avoiding the summer monsoon (which would have blocked

3080-478: The main factors determining ocean currents. The thermohaline circulation (THC) ( thermo- referring to temperature and -haline referring to salt content ) connects the ocean basins and is primarily dependent on the density of sea water . It is becoming more common to refer to this system as the 'meridional overturning circulation' because it more accurately accounts for other driving factors beyond temperature and salinity. Oceanic heat content (OHC) refers to

3150-520: The northern latitudes where the westerly winds will bring the seafarers towards the western coasts of Europe. The secrecy involving the Portuguese navigations, with the death penalty for the leaking of maps and routes, concentrated all sensitive records in the Royal Archives, completely destroyed by the Lisbon earthquake of 1775 . However, the systematic nature of the Portuguese campaign, mapping

3220-694: The ocean and also as sea ice). Because the EGC runs through the Greenland Sea and eventually through the Labrador Sea (as the West Greenland Current) it can have strong implications for the strengthening and or weakening of deep water formation in the Greenland and Labrador Seas. The Meridional Overturning Circulation is a density driven circulation in which a small perturbation in the density field could easily slow down or speed up

3290-480: The ocean's physical attributes including temperature-salinity structure, mixing, surface waves , internal waves, surface tides , internal tides , and currents . The following are central topics investigated by physical oceanography. Since the early ocean expeditions in oceanography, a major interest was the study of ocean currents and temperature measurements. The tides , the Coriolis effect , changes in direction and strength of wind , salinity, and temperature are

3360-412: The oceans was primarily for cartography and mainly limited to its surfaces and of the animals that fishermen brought up in nets, though depth soundings by lead line were taken. The Portuguese campaign of Atlantic navigation is the earliest example of a systematic scientific large project, sustained over many decades, studying the currents and winds of the Atlantic. The work of Pedro Nunes (1502–1578)

3430-402: The pH (now below 8.1 ) through ocean acidification. The pH is expected to reach 7.7 by the year 2100. An important element for the skeletons of marine animals is calcium , but calcium carbonate becomes more soluble with pressure, so carbonate shells and skeletons dissolve below the carbonate compensation depth . Calcium carbonate becomes more soluble at lower pH, so ocean acidification

3500-705: The polar regions and Africa , so too did the mysteries of the unexplored oceans. The seminal event in the founding of the modern science of oceanography was the 1872–1876 Challenger expedition . As the first true oceanographic cruise, this expedition laid the groundwork for an entire academic and research discipline. In response to a recommendation from the Royal Society , the British Government announced in 1871 an expedition to explore world's oceans and conduct appropriate scientific investigation. Charles Wyville Thomson and Sir John Murray launched

3570-700: The recirculation of the EGC in the Greenland Sea via the Jan Mayen Fracture Zone helps lead to a freshening of the central Greenland Sea, however, Rudels et al. disproved this theory and said it must be due to solid sea ice melt and precipitation in the central Greenland Sea. Water masses An oceanographic water mass is an identifiable body of water with a common formation history which has physical properties distinct from surrounding water. Properties include temperature , salinity , chemical - isotopic ratios, and other physical quantities which are conservative flow tracers . Water mass

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3640-474: The rest of her career. (Russell, 2000) Sverdrup, Johnson and Fleming published The Oceans in 1942, which was a major landmark. The Sea (in three volumes, covering physical oceanography, seawater and geology) edited by M.N. Hill was published in 1962, while Rhodes Fairbridge 's Encyclopedia of Oceanography was published in 1966. The Great Global Rift, running along the Mid Atlantic Ridge,

3710-523: The return route from the western coast of Africa (sequentially called 'volta de Guiné' and 'volta da Mina'); and the references to the Sargasso Sea (also called at the time 'Mar da Baga'), to the west of the Azores , in 1436, reveals the western extent of the return route. This is necessary, under sail, to make use of the southeasterly and northeasterly winds away from the western coast of Africa, up to

3780-410: The route taken by Gama at the time he set sail). Furthermore, there were systematic expeditions pushing into the western Northern Atlantic (Teive, 1454; Vogado, 1462; Teles, 1474; Ulmo, 1486). The documents relating to the supplying of ships, and the ordering of sun declination tables for the southern Atlantic for as early as 1493–1496, all suggest a well-planned and systematic activity happening during

3850-633: The salinity is around 34.9 psu. The deep water masses (>1600 m) 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 waters north of Iceland unhindered. It is important to note that these recirculated deep water masses in

3920-619: The scientific community to assess the role of the oceanic processes in the global climate by the reconstruction of past climate at various intervals. Paleoceanographic research is also intimately tied to palaeoclimatology. The earliest international organizations of oceanography were founded at the turn of the 20th century, starting with the International Council for the Exploration of the Sea created in 1902, followed in 1919 by

3990-400: The shifting conditions of the near future. Of particular concern is the manner in which the combination of acidification with the expected additional stressors of higher ocean temperatures and lower oxygen levels will impact the seas. Geological oceanography is the study of the geology of the ocean floor including plate tectonics and paleoceanography . Physical oceanography studies

4060-486: The study of marine meteorology, navigation , and charting prevailing winds and currents. His 1855 textbook Physical Geography of the Sea was one of the first comprehensive oceanography studies. Many nations sent oceanographic observations to Maury at the Naval Observatory, where he and his colleagues evaluated the information and distributed the results worldwide. Knowledge of the oceans remained confined to

4130-530: The submersible DSV  Alvin . In the 1950s, Auguste Piccard invented the bathyscaphe and used the bathyscaphe Trieste to investigate the ocean's depths. The United States nuclear submarine Nautilus made the first journey under the ice to the North Pole in 1958. In 1962 the FLIP (Floating Instrument Platform), a 355-foot (108 m) spar buoy, was first deployed. In 1968, Tanya Atwater led

4200-463: The surface) 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. 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 and it increases to about 35 psu at 1000 meters. The Atlantic water that is seen in

4270-400: The topmost few fathoms of the water and a small amount of the bottom, mainly in shallow areas. Almost nothing was known of the ocean depths. The British Royal Navy 's efforts to chart all of the world's coastlines in the mid-19th century reinforced the vague idea that most of the ocean was very deep, although little more was known. As exploration ignited both popular and scientific interest in

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4340-418: The transport of water southward ranged from 2–32 sverdrups . 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 (<800 m) 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

4410-623: The water type of the source and the standard deviations of the temperature and salinity. It can take many years to establish the standard deviations of the water mass and requires constant surveillance. Once all of the necessary measures are completed, the data will now determine what the current density of the water is and help further classify the water mass. Oceanography Oceanography (from Ancient Greek ὠκεανός ( ōkeanós )  ' ocean ' and γραφή ( graphḗ )  ' writing '), also known as oceanology , sea science , ocean science , and marine science ,

4480-415: The world ocean are: Although there are many types of water masses, they all share characteristics. Water Masses are formed from regions of water having different temperatures. When ice is being formed in a cold climate like Antarctica, the cold temperatures separate the molecular bonds of the water causing it to become less dense. However, because water increases its volume by about 9% when frozen, this makes

4550-434: The world ocean through further scientific study enables better stewardship and sustainable utilization of Earth's resources. The Intergovernmental Oceanographic Commission reports that 1.7% of the total national research expenditure of its members is focused on ocean science. The study of oceanography is divided into these five branches: Biological oceanography investigates the ecology and biology of marine organisms in

4620-683: Was built in 1882. In 1893, Fridtjof Nansen allowed his ship, Fram , to be frozen in the Arctic ice. This enabled him to obtain oceanographic, meteorological and astronomical data at a stationary spot over an extended period. In 1881 the geographer John Francon Williams published a seminal book, Geography of the Oceans . Between 1907 and 1911 Otto Krümmel published the Handbuch der Ozeanographie , which became influential in awakening public interest in oceanography. The four-month 1910 North Atlantic expedition headed by John Murray and Johan Hjort

4690-604: Was discovered by Maurice Ewing and Bruce Heezen in 1953 and mapped by Heezen and Marie Tharp using bathymetric data; in 1954 a mountain range under the Arctic Ocean was found by the Arctic Institute of the USSR. The theory of seafloor spreading was developed in 1960 by Harry Hammond Hess . The Ocean Drilling Program started in 1966. Deep-sea vents were discovered in 1977 by Jack Corliss and Robert Ballard in

4760-627: Was the Report Of The Scientific Results of the Exploring Voyage of H.M.S. Challenger during the years 1873–76 . Murray, who supervised the publication, described the report as "the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries". He went on to found the academic discipline of oceanography at the University of Edinburgh , which remained

4830-400: Was the most ambitious research oceanographic and marine zoological project ever mounted until then, and led to the classic 1912 book The Depths of the Ocean . The first acoustic measurement of sea depth was made in 1914. Between 1925 and 1927 the "Meteor" expedition gathered 70,000 ocean depth measurements using an echo sounder, surveying the Mid-Atlantic Ridge. In 1934, Easter Ellen Cupp ,

4900-420: Was to overcome this problem and clear the passage to India around Africa as a viable maritime trade route, that a systematic plan of exploration was devised by the Portuguese. The return route from regions south of the Canaries became the ' volta do largo' or 'volta do mar '. The 'rediscovery' of the Azores islands in 1427 is merely a reflection of the heightened strategic importance of the islands, now sitting on

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