Arctic Ocean

The Arctic Ocean, located mostly in the Arctic north polar region, is the smallest of the world's five oceans and the shallowest. Even though the International Hydrographic Organization (IHO) recognizes it as an ocean, oceanographers may call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it as one of the Mediterranean seas of the Atlantic Ocean.

Much of the ocean is covered by sea ice, either during the colder months or year-round. Little marine life exists where the ocean surface is covered with ice throughout the year. The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major seas, due to low evaporation, as well as limited outflow to the world ocean with heavy freshwater inflow. The summer shrinking of the icepack has been quoted at 50%.

The Arctic Ocean occupies a roughly circular basin and covers an area of about 14,056,000 square km (5,440,000 mi²), slightly less than 1.5 times the size of the United States. The coastline length is 45,389 kilometers (28,203 mi). Nearly landlocked, it is surrounded by the land masses of Eurasia, North America, Greenland, and several islands. It includes 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.

An underwater mid-ocean ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two basins: the Eurasian, or Nansen, Basin, (after Fridtjof Nansen) which is between 4,000 and 4,500 meters (13,000 and 15,000 ft) deep, and the North American, or Hyperborean, Basin, which is about 4,000 meters (13,000 ft) deep. The bathymetry of the ocean bottom is marked by fault-block ridges, plains of the abyssal zone, ocean deeps, and basins. The average depth of the Arctic Ocean is 1,038 meters (3,407 ft).The deepest point is in the Eurasian Basin deepest point, at 5,450 meters (17,881 ft).

The Arctic Ocean contains a major chokepoint in the southern Chukchi Sea, which provides northern access to the Pacific Ocean via the Bering Strait between North America and Russia. The Arctic Ocean also provides the shortest marine link between the extremes of eastern and western Russia. There are several floating research stations in the Arctic, operated by the U.S. and Russia.

The greatest inflow of water comes from the Atlantic by way of the Norwegian Current, which then flows along the Eurasian coast. Water also enters from the Pacific via the Bering Strait. The East Greenland Current carries the major outflow. Ice covers most of the ocean surface year-round, causing subfreezing temperatures much of the time. The Arctic is a major source of very cold air that inevitably moves toward the equator, meeting with warmer air in the middle latitudes and causing rain and snow. Marine life abounds in open areas, especially the more southerly waters. The ocean's major ports are the Russian cities of Murmansk and Arkhangelsk.

Atlantic Ocean

The Atlantic Ocean is the second-largest ocean, covering approximately one-fifth of the Earth's surface. The ocean's name, derived from Greek mythology, means the "Sea of Atlas." The oldest known mention of this name is contained in The Histories of Herodotus around 450 BC (I 202).

This ocean occupies an elongated, S-shaped basin extending in a north-south direction and is divided into the North Atlantic and South Atlantic by Equatorial Counter Currents at about 8° North latitude. Bounded by the Americas on the west and Europe and Africa on the east, the Atlantic is linked to the Pacific Ocean by the Arctic Ocean on the north and the Drake Passage on the south. A man-made connection between the Atlantic and Pacific is provided by the Panama Canal. On the east, the dividing line between the Atlantic and the Indian Ocean is the 20° East meridian, running south from Cape Agulhas to Antarctica. The Atlantic is separated from the Arctic by a line from Greenland to northwestern Iceland and then from northeastern Iceland to the southernmost tip of Spitsbergen and then to North Cape in northern Norway.

Covering approximately 20% of Earth's surface, the Atlantic Ocean is second only to the Pacific in size. 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 area that drains into the Atlantic is four times that of either the Pacific or Indian oceans. The volume of the Atlantic Ocean with its adjacent seas is 354,700,000 cubic kilometres (85,100,000 cu mi) and without them 323,600,000 cubic kilometres (77,640,000 cu mi).

The average depths of the Atlantic, with its adjacent seas, is 3,338 metres (10,932 ft); without them it is 3,926 metres (12,881 ft). The greatest depth, 8,605 metres (28,232 ft), is in the Puerto Rico Trench. The width of the Atlantic varies from 2,848 kilometres (1,770 mi) between Brazil and Liberia to about 4,830 kilometres (3,000 mi) between the United States and northern Africa.

Indian Ocean

The Indian Ocean is the third largest body of water in the world, covering about 20% of the Earth's water surface. It is bounded on the north by Southern Asia (including the Indian subcontinent, hence its name); on the west by the Arabian Peninsula and Africa; on the east by the Malay Peninsula, the Sunda Islands, and Australia; and on the south by the Southern Ocean. It is separated from the Atlantic Ocean by the 20° east meridian running south from Cape Agulhas, and from the Pacific by the 147° east meridian. The northernmost extent of the Indian Ocean is approximately 30° north latitude in the Persian Gulf. This ocean is nearly 10,000 kilometers (6,200 mi) wide at the southern tips of Africa and Australia; its area is 73,556,000 square kilometers (28,400,000 mi²), including the Red Sea and the Persian Gulf.

The ocean's volume is estimated to be 292,131,000 cubic kilometers (70,086,000 mi3). Small islands dot the continental rims. Island nations within the ocean are Madagascar (formerly Malagasy Republic), the world's fourth largest island; Comoros; Seychelles; Maldives; Mauritius; and Sri Lanka. Indonesia borders it. The ocean's importance as a transit route between Asia and Africa has made it a scene of conflict. Because of its size, however, no nation had successfully dominated most of it until the early 1800s when Britain controlled much of the surrounding land. After World War II, the ocean has been dominated by India and Australia.

The African, Indian, and Antarctic crustal plates converge in the Indian Ocean. 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 kilometers (125 mi) in width. An exception is found off Australia's western coast, where the shelf width exceeds 1,000 kilometers (600 mi). The average depth of the ocean is 3,890 meters (12,760 ft). Its deepest point, in the Java Trench, is estimated to be 7,450 meters (24,442 ft) below sea level. 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.

A spring 2000 decision by the International Hydrographic Organization delimited a fifth world ocean, stripping the southern portions of the Indian Ocean. The new ocean extends from the coast of Antarctica north to 60° south latitude which coincides with the Antarctic Treaty Limit. The Indian Ocean remains the third-largest of the world's five oceans.

Major chokepoints include Bab el Mandeb, Strait of Hormuz, Strait of Malacca, southern access to the Suez Canal, and the Lombok Strait. Seas include Andaman Sea, Arabian Sea, Bay of Bengal, Great Australian Bight, Gulf of Aden, Gulf of Oman, Laccadive Sea, Mozambique Channel, Persian Gulf, Red Sea, Strait of Malacca, and other tributary water bodies.

Pacific Ocean

The Pacific Ocean (from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan) is the world's largest body of water.

The ocean encompasses a third of the Earth's surface, having an area of 179.7 million square kilometres (69.4 million sq mi and 161 million cubic mi) —significantly larger than Earth's entire landmass, with room for another Africa to spare. Extending approximately 15,500 kilometres (9,600 mi) from the Bering Sea in the Arctic to the icy margins of Antarctica's Ross Sea in the south (although the Antarctic regions of the Pacific are sometimes described as part of the circumpolar Southern Ocean), the Pacific reaches its greatest east-west width at about 5°N latitude, where it stretches approximately 19,800 kilometres (12,300 mi) from Indonesia to the coast of Colombia and Peru. The western limit of the ocean is often placed at the Strait of Malacca. The lowest point on earth—the Mariana Trench—lies 10,911 metres (35,797 ft) below sea level. Its average depth is 4,300 metres (14,000 ft).

The shoreline at Palm Beach, New South WalesThe Pacific contains about 25,000 islands (more than the total number in the rest of the world's oceans combined), the majority of which are found south of the equator.

The Pacific Ocean is currently shrinking from plate tectonics, while the Atlantic Ocean is increasing in size.

Along the Pacific Ocean's irregular western margins lie many seas, the largest of which are the Celebes Sea, Coral Sea, East China Sea, Philippine Sea, Sea of Japan, South China Sea, Sulu Sea, Tasman Sea, and Yellow Sea. The Strait of Malacca joins the Pacific and the Indian Oceans on the west, and the Strait of Magellan links the Pacific with the Atlantic Ocean on the east. To the north, the Bering Strait connects the Pacific with the Arctic Ocean.

As the Pacific straddles the ± 180° meridian, the West Pacific (or western Pacific, near Asia) is actually in the Eastern Hemisphere, while the East Pacific (or eastern Pacific, near the Americas) is actually in the Western Hemisphere.

Coastal area of Viña del Mar, ChileFor most of Magellan's voyage from the Strait of Magellan to the Philippines, the explorer indeed found the ocean peaceful. However, the Pacific is not always peaceful. Many tropical cyclones (typhoons, the equivalent of Atlantic hurricanes), batter the islands of the Pacific. The lands around the Pacific rim are full of volcanoes and often affected by earthquakes. Tsunamis, caused by underwater earthquakes, have devastated many islands and destroyed entire towns.

Southern Ocean

The Southern Ocean, also known as the South Polar Ocean (and formerly the Antarctic Ocean), is the body of water encircling the continent of Antarctica. It is the world's fourth largest ocean and the latest to be defined, having been accepted by a decision of the International Hydrographic Organization (IHO) in 2000, though the term has long been traditional among mariners. This change reflects the recent findings in oceanography of the importance of ocean currents.

The Southern Ocean is oceanographically defined as an ocean connected with the Antarctic Circumpolar Current, which circulates around Antarctica. It includes Amundsen Sea, Bellingshausen Sea, part of the Drake Passage, Ross Sea, a small part of the Scotia Sea, and Weddell Sea. The total area is 20,327,000 square kilometers (7,848,000 mi²)

The Southern Ocean is located in the Southern Hemisphere possessing typical depths between 4,000—5,000 meters (13,000 to 16,000 ft) deep over most of its extent with only limited areas of shallow water. The Antarctic continental shelf is generally narrow and unusually deep, its edge lying at depths up to 800 meters (2,600 ft), compared to a global mean of 133 meters (436 ft).

Solstice to solstice in line with the sun's seasonal influence, the Antarctic ice pack fluctuates from an average minimum of 2.6 million square kilometers (1.0 million mi²) in March to about 18.8 million square kilometers (7.2 million mi²) in September, more than a sevenfold increase in area.

The Antarctic Circumpolar Current moves perpetually eastward—chasing and joining itself, and at 21,000 kilometers (13,000 mi) in length— it is the world's longest ocean current, transporting 130 million cubic meters (4.6 billion ft³) of water per second—100 times the flow of all the world's rivers.

Its greatest depth is 7,235 meters (23,737 ft) at the southern end of the South Sandwich Trench, at 60°00'S, 024°W.

-wikipedia.org

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