ARCTIC OCEAN

Speciality

The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions. The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions.The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean.Almost completely surrounded by Eurasia and North America, the Arctic Ocean is partly covered by sea ice throughout the year[4] (and almost completely in winter). The Arctic Ocean's surface temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major oceans, due to low evaporation, heavy fresh water inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the ice has been quoted at 50%.The US National Snow and Ice Data Center (NSIDC) uses satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years.

History

For much of European history, the north polar regions remained largely unexplored and their geography conjectural. Pytheas of Massilia recorded an account of a journey northward in 325 BC, to a land he called "Eschate Thule," where the Sun only set for three hours each day and the water was replaced by a congealed substance "on which one can neither walk nor sail." He was probably describing loose sea ice known today as "growlers" or "bergy bits;" his "Thule" was probably Norway, though the Faroe Islands or Shetland have also been suggested.Early cartographers were unsure whether to draw the region around the North Pole as land (as in Johannes Ruysch's map of 1507, or Gerardus Mercator's map of 1595) or water (as with Martin Waldseemüller's world map of 1507). The fervent desire of European merchants for a northern passage, the Northern Sea Route or the Northwest Passage, to "Cathay" (China) caused water to win out, and by 1723 mapmakers such as Johann Homann featured an extensive "Oceanus Septentrionalis" at the northern edge of their charts.The few expeditions to penetrate much beyond the Arctic Circle in this era added only small islands, such as Novaya Zemlya (11th century) and Spitsbergen (1596), though since these were often surrounded by pack-ice, their northern limits were not so clear. The makers of navigational charts, more conservative than some of the more fanciful cartographers, tended to leave the region blank, with only fragments of known coastline sketched in.

This lack of knowledge of what lay north of the shifting barrier of ice gave rise to a number of conjectures. In England and other European nations, the myth of an "Open Polar Sea" was persistent. John Barrow, longtime Second Secretary of the British Admiralty, promoted exploration of the region from 1818 to 1845 in search of this.

Geography

The Arctic Ocean occupies a roughly circular basin and covers an area of about 14,056,000 km2 (5,427,000 sq mi), almost the size of Russia. The coastline is 45,390 km (28,200 mi) long.[9][11] It is surrounded by the land masses of Eurasia, North America, Greenland, and by several islands.It is generally taken to include Baffin Bay, Barents Sea, Beaufort Sea, Chukchi Sea, East Siberian Sea, Greenland Sea, Hudson Bay, Hudson Strait, Kara Sea, Laptev Sea, White Sea and other tributary bodies of water. It is connected to the Pacific Ocean by the Bering Strait and to the Atlantic Ocean through the Greenland Sea and Labrador Sea.Countries bordering the Arctic Ocean are: Russia, Norway, Iceland, Greenland, Canada and the United States.

ATLANTIC OCEAN

Speciality

The Atlantic Ocean is the world's second largest ocean, behind the Pacific Ocean. With a total area of about 106,400,000 square kilometres, it covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. The Atlantic Ocean is the world's second largest ocean, behind the Pacific Ocean. With a total area of about 106,400,000 square kilometres (41,100,000 sq mi), it covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. The first part of its name refers to Atlas of Greek mythology, making the Atlantic the "Sea of Atlas".The oldest known mention of "Atlantic" is in The Histories of Herodotus around 450 BC (Hdt. 1.202.4): Atlantis thalassa (Greek: Ἀτλαντὶς θάλασσα; English: Sea of Atlas). The term Ethiopic Ocean, derived from Ethiopia, was applied to the southern Atlantic as late as the mid-19th century. Before Europeans discovered other oceans, their term "ocean" was synonymous with the waters beyond the Strait of Gibraltar that are now known as the Atlantic. The early Greeks believed this ocean to be a gigantic river encircling the world.

Geography

The Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Strait, Greenland Sea, Norwegian Sea and Barents Sea. To the east, the boundaries of the ocean proper are Europe: the Strait of Gibraltar (where it connects with the Mediterranean Sea–one of its marginal seas–and, in turn, the Black Sea, both of which also touch upon Asia) and Africa.

In the southeast, the Atlantic merges into the Indian Ocean. The 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. Some authorities show it extending south to Antarctica, while others show it bounded at the 60° parallel by the Southern Ocean.In the southwest, the Drake Passage connects it to the Pacific Ocean. The man-made Panama Canal links the Atlantic and Pacific. Besides those mentioned, other large bodies of water adjacent to the Atlantic are the Caribbean Sea, the Gulf of Mexico, Hudson Bay, the Arctic Ocean, the Mediterranean Sea, the North Sea, the Baltic Sea, and the Celtic Sea.Covering approximately 22% of Earth's surface, the Atlantic is second in size to the Pacific. With its adjacent seas, it occupies an area of about 106,400,000 square kilometres (41,100,000 sq mi); without them, it has an area of 82,400,000 square kilometres (31,800,000 sq mi). The land that drains into the Atlantic covers four times that of either the Pacific or Indian oceans. The volume of the Atlantic with its adjacent seas is 354,700,000 cubic kilometers (85,100,000 cu mi) and without them

Ocean floor

The principal feature of the bathymetry (bottom topography) is a submarine mountain range called the Mid-Atlantic Ridge.[6] It extends from Iceland in the north to approximately 58° South latitude, reaching a maximum width of about 860 nautical miles (1,590 km; 990 mi). A great rift valley also extends along the ridge over most of its length. The depth of water at the apex of the ridge is less than 2,700 metres (1,500 fathoms; 8,900 ft) in most places, while the bottom of the ridge is three times as deep. Several peaks rise above the water and form islands. The South Atlantic Ocean has an additional submarine ridge, the Walvis Ridge.The Mid-Atlantic Ridge separates the Atlantic Ocean into two large troughs with depths from 3,700–5,500 metres (2,000–3,000 fathoms; 12,100–18,000 ft). Transverse ridges running between the continents and the Mid-Atlantic Ridge divide the ocean floor into numerous basins. Some of the larger basins are the Blake, Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic. The largest South Atlantic basins are the Angola, Cape,Argentina, and Brazil basins.The deep ocean floor is thought to be fairly flat with occasional deeps, abyssal plains, trenches, seamounts, basins, plateaus, canyons, and some guyots. Various shelves along the margins of the continents constitute about 11% of the bottom topography with few deep channels cut across the continental rise.

PACIFIC OCEAN

Speciality

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.25 million square kilometres (63.8 million square miles) in area, this largest division of the World Ocean – and, in turn, the hydrosphere – covers about 46% of the Earth's water surface and about one-third of its total surface area, making it larger than all of the Earth's land area combined. The equator subdivides it into the North Pacific Ocean and South Pacific Ocean, with two exceptions: the Galápagos and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific. The Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres (35,797 ft).[3]The eastern Pacific Ocean was first sighted by Europeans in the early 16th century when Spanish explorer Vasco Núñez de Balboa crossed the Isthmus of Panama in 1513 and discovered the great "southern sea" which he named Mar del Sur. The ocean's current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He therefore called it Mar Pacifico in Portuguese, meaning "peaceful sea.

History

Important human migrations occurred in the Pacific in prehistoric times. About 3000 BC speakers of the Austronesian languages, probably on the island of Taiwan, mastered the art of long-distance canoe travel and spread themselves, or their languages, south to the Philippines and Indonesia and east to the islands of Micronesia and Melanesia. The greatest migrations took place through the Polynesians, from the Asian edge of the ocean to Tahiti, Hawaii, New Zealand, Easter Island and possibly even America.

Long-distance trade developed all along the coast from Mozambique to Japan. Trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of this trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality. From 1404 to 1433 Zheng He led expeditions into the Indian Ocean.

The Martin Waldseemüller map of 1507 was the first to show the Americas separating two distinct oceans.

The direct contact of the European fleets with western edges of the Pacific began with the Portuguese expeditions of António de Abreu and Francisco Serrão to the Maluku Islands in 1512, and with Jorge Álvares's expedition to southern China in 1513,both ordered by Afonso de Albuquerque. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa. His expedition crossed the Isthmus of Panama and reached the Pacific Ocean in 1513.He named it Mar del Sur (literally, "Sea of the South", or South Sea).

Geography

The Pacific separates Asia and Australia from the Americas. It may be further subdivided by the equator into northern (North Pacific) and southern (South Pacific) portions. It extends from the Antarctic region in the South to the Arctic in the north. The Pacific Ocean encompasses approximately one-third of the Earth's surface, having an area of 165.2 million square kilometres (63.8 million square miles) —significantly larger than Earth's entire landmass of some 150 million square kilometres (58 million square miles

SOTHERN OCEAN

Speciality

The Southern Ocean (also known as the Great Southern Ocean, Antarctic Ocean, South Polar Ocean and Austral Ocean) comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. As such, it is regarded as the fourth-largest of the five principal oceanic divisions (after the Pacific, Atlantic, and Indian Oceans, but larger than the Arctic Ocean). This ocean zone is where cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters.Geographers disagree on the Southern Ocean's northern boundary, and some even its existence—considering the waters part of the Pacific, Atlantic, and Indian Oceans instead. Others regard the Antarctic Convergence, an ocean zone which fluctuates seasonally, as separating the Southern Ocean from other oceans, rather than the 60th parallel.Australian authorities regard the Southern Ocean as lying immediately south of Australia.

History of exploration

Exploration of the Southern Ocean was inspired by a belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe, Asia and North Africa—which had existed since the times ofPtolemy. The doubling of the Cape of Good Hope in 1487 by Bartolomeu Dias first brought explorers within touch of the Antarctic cold, and proved that there was an ocean separating Africa from any Antarctic land that might exist. Ferdinand Magellan, who passed through the Strait of Magellan in 1520, assumed that the islands of Tierra del Fuego to the south were an extension of this unknown southern land. In 1564, Abraham Ortelius published his first map, Typus Orbis Terrarum, an eight-leaved wall map of the world, on which he identified the Regio Patalis with Locach as a northward extension of the Terra Australis, reaching as far as New Guinea.

European geographers continued to connect the coast of Tierra del Fuego with the coast of New Guinea on their globes, and allowing their imaginations to run riot in the vast unknown spaces of the south Atlantic, south Indian and Pacific oceans they sketched the outlines of the Terra Australis Incognita ("Unknown Southern Land"), a vast continent stretching in parts into the tropics. The search for this great south land or Third World was a leading motive of explorers in the 16th and the early part of the 17th centuries.

South of the Antarctic Convergence

The visit to South Georgia by Anthony de la Roché in 1675 was the first ever discovery of land south of the Antarctic Convergence i.e. in the Southern Ocean / Antarctic. Soon after the voyage cartographers started to depict ‘Roché Island’, honouring the discoverer. James Cook was aware of la Roché's discovery when surveying and mapping the island in 1775.

Edmond Halley's voyage in HMS Paramour for magnetic investigations in the South Atlantic met the pack ice in 52° S in January 1700, but that latitude (he reached 140 mi off the north coast of South Georgia) was his farthest south. A determined effort on the part of the French naval officer Jean-Baptiste Charles Bouvet de Lozier to discover the "South Land" – described by a half legendary "sieur de Gonneyville" – resulted in the discovery of Bouvet Island in 54°10′ S, and in the navigation of 48° of longitude of ice-cumbered sea nearly in 55° S in 1730 .

In 1771, Yves Joseph Kerguelen sailed from France with instructions to proceed south from Mauritius in search of "a very large continent." He lighted upon a land in 50° S which he called South France, and believed to be the central mass of the southern continent. He was sent out again to complete the exploration of the new land, and found it to be only an inhospitable island which he renamed the Isle of Desolation, but which was ultimately named after him.

INDIAN OCEAN

Speciality

he Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded by Asia—including India, after which the ocean is named—on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean (or, depending on definition, by Antarctica).As one component of the World Ocean, the Indian Ocean is delineated from the Atlantic Ocean by the 20° east meridian running south from Cape Agulhas, and from the Pacific Ocean by the meridian of 146°55' east The northernmost extent of the Indian Ocean is approximately 30° north in the Persian Gulf. The ocean is nearly 10,000 km (6200 mi) wide at the southern tips of Africa and Australia, and its area is 73,556,000 km² (28,350,000 mi²), including the Red Sea and the Persian Gulf.The Indian Ocean's volume is estimated to be 292,131,000 km³ (70,086,000 mi³). Small islands dot the continental rims. Island nations within the ocean are Madagascar (the world's fourth largest island), Bahrain, Comoros, Maldives, Mauritius, Seychelles and Sri Lanka. The archipelago of Indonesia and the island nation of Timor-Leste border the ocean on the east. Geography
The African, Indian, and Antarctic crustal plates converge in the Indian Ocean at the Rodrigues Triple Point. Their junctures are marked by branches of the mid-oceanic ridge forming an inverted Y, with the stem running south from the edge of the continental shelf near Mumbai, India. The eastern, western, and southern basins thus formed are subdivided into smaller basins by ridges.The ocean's continental shelves are narrow, averaging 200 kilometres (125 mi) in width. An exception is found off Australia's western coast, where the shelf width exceeds 1,000 kilometres (600 mi). The average depth of the ocean is 3,890 m (12,762 ft). Its deepest point is Diamantina Deep in Diamantina Trench, at 8,047 m (26,401 ft) deep; also sometimes considered is Sunda Trench, at a depth of 7,258–7,725 m (23,812–25,344 ft).[10] North of 50° south latitude, 86% of the main basin is covered by pelagic sediments, of which more than half is globigerina ooze. The remaining 14% is layered with terrigenous sediments. Glacial outwash dominates the extreme southern latitudes. Hydrology
Among the few large rivers flowing into the Indian Ocean are the Zambezi, Shatt al-Arab, Indus, Narmada, Ganges, Brahmaputra, Jubba and Irrawaddy River. The ocean's currents are mainly controlled by the monsoon. Two large circular currents, one in the northern hemisphere flowing clockwise and one south of the equator moving anticlockwise, constitute the dominant flow pattern. 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, and Antarctic currents. North of 20° south latitude the minimum surface temperature is 22 °C (72 °F), exceeding 28 °C (82 °F) 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. Pack ice and icebergs are found throughout the year south of about 65° south lSSSatitude. The average northern limit of icebergs is 45° south latitude.

BEAUFORT SEA

Speciality

The Beaufort Sea is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort.The Beaufort Sea (French: mer de Beaufort) is a marginal sea of the Arctic Ocean,[3] located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort. The major Mackenzie River empties into the Canadian part of the sea, west of Tuktoyaktuk, which is one of the few permanent settlements on the sea shores.The sea, characterized by severe climate, is frozen over most of the year. Historically, only a narrow pass up to 100 km (62 mi) opened in August–September near its shores, but recently due to climate change in the Arctic the ice-free area in late summer has greatly enlarged. The seacoast was populated about 30,000 years ago, but the population density is very low. The sea contains significant resources of petroleum and natural gas under its shelf, such as the Amauligak field. They were discovered in the period between the 1950s and 1980s, and their exploration became the major human activity in the area since the 1980s.

Geography

Several rivers such as the Kongakut River in Alaska and the Firth River in Yukon empty into the Beaufort. The major river to flow into the sea is the Mackenzie, Canada's longest, which empties into the Canadian part of the sea, west of Tuktoyaktuk. The coastal shelf area is rather narrow, especially near and east of Point Barrow in the Alaskan part of the sea, and contains numerous submarine valleys. It becomes wider near the delta of the Mackenzie River but nowhere exceeds 145 km (90 mi). Near the coast, the depths are shallower than 60 m (200 ft) but they rapidly increase northwards up to a few kilometers, transforming into a massive platform which is geologically similar to that of the oceans. There are many small islands in the sea and in the delta of the Mackenzie River. A few larger ones lie west of the Mackenzie River, such as Herschel Island (4 km (2.5 mi) off the shore, area 18 km2 (6.9 sq mi)) and Barter Island (0.3 km (0.19 mi) from the coast, area 13 km2 (5.0 sq mi)). The coasts are low, with the maximum elevations between 250 and 750 m (820 and 2,460 ft).[2] The soil is frozen all year around at the depth below about 1 m (3 ft 3 in) or less, forming permafrost, and only top few tens centimeters thaws in summer. Consequently, buildings have to be elevated above ground on wooden piles that are immersed into the permafrost.

Human activities

The Beaufort Sea coasts were populated about 30,000 years ago by migrating aboriginal peoples from Siberia. Later, around 9,000 years ago, they were replaced by Indians, 4,000 years ago by Paleo-Eskimos such as the Dorset culture, around 1,000 years ago by the Thule and finally by the modern Inuit. From early ages, they practised fishing – bones of Arctic char were found at the 4,000 years old settlements. While originally they lived nomadic life, later, they started to form permanent settlements. Modern Inuit are mostly concentrated near the Mackenzie River delta. Their population is increasing, but the unemployment rate is relatively highBowhead whales were hunted in the sea between 1888 and 1914. This practice stopped, first because of the decline in whale population and then because of government regulations, but resumed in the 1990s.The major settlements along the Beaufort Sea are Tuktoyaktuk (population 930 in 2009 in Canada and Prudhoe Bay, Alaska. Although Prudhoe Bay is permanently populated by only a few people, there are thousands of contract workers in the area employed on petroleum production at the Prudhoe Bay Oil Field, which is on the coastal lowland known as the North Slope. Artificial islands, such as Endicott and Northstar, have been raised near the shores in 1987 and 2001, respectively. The crude oil is transported through the Trans-Alaska Pipeline System to the southern port of Valdez

BARENTS SEA

Speciality

The Barents Sea is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents.The Barents Sea (Norwegian: Barentshavet; Russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents. It is a rather deep shelf sea (average depth 760 feet (230 m) and maximum depth 1,480 feet (450 m)), bordered by the shelf edge towards the Norwegian Sea in the west, the islands of Svalbard (Norway) in the northwest, and the islands of Franz Josef Land and Novaya Zemlya (Arkhangelsk Oblast) in the northeast and east. Novaya Zemlya separates the Kara Sea from the Barents Sea. Significant fossil fuel energy resources exist in the Barents Sea region.

Geography

The southern half of the Barents Sea, including the ports of Murmansk (Russia) and Vardø (Norway) remain ice-free year round due to the warm North Atlantic drift. In September, the entire Barents Sea is more or less completely ice-free. Until the Winter War (1939–40), Finland's territory also reached to the Barents Sea, with the harbor at Petsamo being Finland's only ice-free winter harbor.There are three main types of water masses in the Barents Sea: Warm, salty Atlantic water (temperature >3°C, salinity >35) from the North Atlantic drift, cold Arctic water (temperature <0°C, salinity <35) from the north, and warm, but not very salty coastal water (temperature >3°C, salinity <34.7). Between the Atlantic and Polar waters, a front called the Polar Front is formed. In the western parts of the sea (close to Bear Island), this front is determined by the bottom topography and is therefore relatively sharp and stable from year to year, while in the east (towards Novaya Zemlya), it can be quite diffuse and its position can vary a lot between years.

History

The Barents Sea was formerly known to Russians as Murmanskoye Morye, or the "Sea of Murmans" (i.e., Norwegians), and it appears with this name in sixteenth-century maps, including Gerard Mercator's Map of the Arctic published in his 1595 atlas. Its eastern corner, in the region of the Pechora River's estuary, has been known as Pechorskoye Morye, that is, Pechora Sea.This sea was given its present name in honor of Willem Barents, a Dutch navigator and explorer. Barents was the leader of early expeditions to the far north, at the end of the sixteenth century. Seabed mapping was completed in 1933 with the first full map produced by Russian marine geologist Maria Klenova.The Barents Sea was also the site of a notable World War II engagement, a German surface merchant raiding attack on a British convoy that later became known as the Battle of the Barents Sea. Under the command of Oskar Kummetz, the German warships sank minelayer HMS Bramble and destroyer HMS Achates (H12), but in turn lost destroyer Z16 Friedrich Eckoldt and Admiral Hipper was severely damaged by British gunfire. The Germans later retreated and the British convoy arrived safely at