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Pacific Ocean Essay, Research Paper

Pacific Ocean

The Pacific Ocean, the world’s largest water body, occupies a third of

the Earth’s surface. Extending approximately 15,500 km (9,600 mi)

from the BERING SEA in the Arctic north to the icy margins of

Antarctica’s Ross Sea in the south, the Pacific reaches its greatest

width at about 5 deg north latitude, where it stretches approximately

19,800 km (12,300 mi) from Indonesia to the coast of Colombia. The

western limit of the ocean is often placed at the Strait of Malacca. The

Pacific contains about 25,000 islands (more than the total number in

the rest of the world’s oceans combined), almost all of which are found

south of the equator. The Pacific covers an area of 179.7 million sq km

(69.4 million sq mi). The lowest known point on Earth, in the

MARIANAS TRENCH, lies within the Pacific.

Along the Pacific Ocean’s irregular margins lie many seas, the largest

of which are the CELEBES SEA, CORAL SEA, East China Sea, Sea

of Japan, SULU 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.

OCEAN BOTTOM

The ocean floor of the central Pacific basin is relatively uniform, with a mean depth of about 4,270 m (14,000 ft). The major

irregularities in the area are the extremely steep-sided, flat-topped submarine peaks known as SEAMOUNTS. The western part of the

floor consists of mountain arcs that rise above the sea as island groups, such as the Solomon Islands and New Zealand, and deep

trenches, such as the Marianas Trench, the Philippine Trench, and the Tonga Trench. Most of the deep trenches lie adjacent to the

outer margins of the wide western Pacific continental shelf.

Along the eastern margin of the Pacific basin is the East Pacific Rise, which is a part of the worldwide mid-oceanic ridge. About

3,000 km (1,800 mi) across, the rise stands about 3 km (2 mi) above the adjacent ocean floor. Because a relatively small land area

drains into the Pacific, and because of the ocean’s immense size, most sediments are authigenic or pelagic in origin. Authigenic

sediments include montmorillonite and phillipsite. Pelagic sediments derived from seawater include pelagic red clays and the skeletal

remains of sea life. Terrigenous sediments are confined to narrow marginal bands close to land.

WATER CHARACTERISTICS

Water temperatures in the Pacific vary from freezing in the poleward areas to about 29 deg C (84 deg F) near the equator. Salinity

also varies latitudinally. Water near the equator is less salty than that found in the mid-latitudes because of abundant equatorial

precipitation throughout the year. Poleward of the temperate latitudes salinity is also low, because little evaporation of seawater

takes place in these areas.

The surface circulation of Pacific waters is generally clockwise in the Northern Hemisphere and counterclockwise in the Southern

Hemisphere. The North Equatorial Current, driven westward along latitude 15 deg north by the trade winds, turns north near the

Philippines to become the warm Kuroshio, or Japan, Current. Turning eastward at about 45 deg north, the Kuroshio forks and some

waters move northward as the ALEUTIAN CURRENT, while the rest turn southward to rejoin the North Equatorial Current. The

Aleutian Current branches as it approaches North America and forms the base of a counterclockwise circulation in the Bering Sea.

Its southern arm becomes the slow, south-flowing California Current.

The South Equatorial Current, flowing west along the equator, swings southward east of New Guinea, turns east at about 50 deg

south latitude, and joins the main westerly circulation of the Southern Pacific, which includes the Earth-circling Antarctic Circumpolar

Current. As it approaches the Chilean coast, the South Equatorial Current divides; one branch flows around Cape Horn and the other

turns north to form the Peru, or Humboldt, Current.

CLIMATE

Only the interiors of the large land masses of Australia, New Guinea, and New Zealand escape the pervasive climatic influence of the

Pacific. Within the area of the Pacific, five distinctively different climatic regions exist: the mid-latitude westerlies, the trades, the

monsoon region, the typhoon region, and the doldrums. Mid-latitude westerly air streams occur in both northerly and southerly

latitudes, bringing marked seasonal differences in temperature. Closer to the equator, where most of the islands lie, steadily blowing

trade winds allow for relatively constant temperatures throughout the year of 21-27 deg C (70-81 deg F).

The monsoon region lies in the far western Pacific between Japan and Australia. Characteristic of this climatic region are winds that

blow from the continental interior to the ocean in winter and in the opposite direction in summer. Consequently, a marked seasonality

of cloudiness and rainfall occurs. Typhoons often cause extensive damage in the west and southwest Pacific. The greatest typhoon

frequency exists within the triangle from southern Japan to the central Philippines to eastern Micronesia. Although more poorly

defined than the other climatic regions, two major doldrum areas lie within the ocean, one located off the western shores of Central

America and the other within the equatorial waters of the western Pacific. Both areas are noted for their high humidity, considerable

cloudiness, light fluctuating winds, and frequent calms.

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