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Though generally described as several ‘separate’ oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria. Thesedivisions are (in descending order of size)

Pacifc Ocean, which separates Asia and Australia from the Americas Atlantic Ocean, which separates the Americas from Europe and Africa Indian Ocean, which washes upon southern Asia and separates Africa and Australia Southern Ocean, sometimes considered an extension of the Pacific, Atlantic and Indian Oceans, which encircles Antarctica. Arctic Ocean, sometimes considered a sea of the Atlantic, which covers much of the Arctic and washes upon northern North America and Eurasia. The Pacific and Atlantic may be further subdivided by the equator into northern and southern portions. Smaller regions of the oceans are called seas, gulfs, bays, straits and other names.

The Pacific Ocean. 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 165.2 million square kilometres (64.1 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). The Pacific Ocean was sighted by Europeans early in the 16th century, first by the Spanish explorer Vasco Núñez de Balboa, who crossed the Isthmus of Panama in 1513 and named it Mar del Sur (South Sea). Its current name was given by Portuguese explorer Ferdinand Magellan during the Spanish expedition of world circumnavigation in 1521, who encountered favourable winds as he reached the ocean and called it Mar Pacifico in Portuguese, meaning “peaceful sea”.

The Atlantic Ocean. The Atlantic Ocean is the second-largest of the world’s oceanic divisions. With a total area of about 106,400,000 square kilometres (41,100,000 sq mi),[1] it covers approximately 20% of the Earth’s surface and about 26% 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 Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and

Africa to the east, and the Americas to the west. As one component of the interconnected global ocean, it is connected in the north to the Arctic Ocean (which is sometimes considered a sea of the Atlantic), to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south. (Other definitions describe the Atlantic as extending southward to Antarctica.) The equator subdivides it into the North Atlantic Ocean and South Atlantic Ocean.

The Indian Ocean. The 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 on the north by the Indian Subcontinent and Arabian Peninsula (or, more generally, by southern and western Asia); on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean (or, depending on

definition, by Antarctica). The ocean is named after the geographic location of India. The ocean's volume is estimated to be 292,131,000 cubic kilometres (70,086,000 mi3). Small islands dot the continental rims. Island nations within the ocean are Madagascar, the world's fourth largest island; Reunion Island; Comoros; Seychelles; Maldives; Mauritius; and Sri Lanka. The archipelago of Indonesia borders the ocean on the east.

The Southern Ocean. The Southern Ocean (also known as the Great Southern Ocean, the Antarctic Ocean, and the South Polar Ocean) comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions. This ocean zone is where cold, northward flowing waters from the Antarctic mix

with warmer sub-Antarctic waters. Geographers disagree on the Southern Ocean’s northern boundary or even its existence, with many 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.

The Arctic Ocean. The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arcticnorth 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 as one of the mediterranean seas 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[3] (and almost completely in winter). 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 oceans, due to low evaporation, heavy freshwater 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.

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