Oceans

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  • GCMD Oceans
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Abstract from DBPedia
    (For other uses, see Ocean (disambiguation).) An ocean (from Ancient Greek Ὠκεανός, transc. Okeanós, the sea of classical antiquity) is a body of saline water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean, which covers almost 71% of its surface. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land. Saline water covers approximately 72% of the planet's surface (~3.6×108 km2) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of Earth's surface and 90% of the Earth's biosphere. The ocean contains 97% of Earth's water, and oceanographers have stated that less than 5% of the World Ocean has been explored. The total volume is approximately 1.35 billion cubic kilometers (320 million cu mi) with an average depth of nearly 3,700 meters (12,100 ft). As it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. It is the habitat of 230,000 known species, although much of the oceans depths remain unexplored, and over two million marine species are estimated to exist. The origin of Earth's oceans remains unknown; oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of Europa is estimated to have over twice the water volume of Earth. The Solar System's giant planets are also thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.

    大洋(たいよう、英: ocean)または大海洋(だいかいよう)・独立海(どくりつかい)は、水圏の大部分を占める、それぞれが接続した地球上の海の主要領域。一般には北極海・太平洋・大西洋・インド洋・南氷洋の5つに区分される。これらの大洋はそれぞれ固有の海流を持ち、また潮汐を発生させる元ともなる。大洋以外の海は副洋 (Nebenmeere) または附属海と呼ばれ、地中海のように大陸の間にある狭い面積の海や紅海のような大陸内部に存在する海、また日本海のように大陸の沿うものまたは北海のような大陸から直角に伸びる海などが当たる。 英語oceanの語源はギリシア語のὨκεανὸς, "okeanos" オーケアノスである。 全大洋面積の過半が深さ4267m程の水深にある。大洋の平均塩分濃度は3.5%程度であり、ほとんどの水域で3.0-3.8%の範囲に入る。科学者による推計では、23万の海洋種が知られており、さらにその10倍の種が存在する可能性がある。 大洋は生物圏に重要な役割を果たす。大洋の蒸発は水循環においてほとんどの降雨の元であり、大洋の温度は気候や風を決定付け、陸地の生物へ影響を与える。

    (Source: http://dbpedia.org/resource/Ocean)

data publication(s) found by GCMD Science Keywords)