Body of salt water covering the majority of Earth

Ocean

Ocean

The ocean (also the <a href="/en/Sea" title="Sea" class="wl">sea</a> or the world ocean) is the body of <a href="/en/Saline_water" title="Saline water" class="wl">salt water</a> that covers approximately 70.8% of the <a href="/en/Earth" title="Earth" class="wl">Earth</a> and contains 97% of <a href="/en/Water_distribution_on_Earth" title="Water distribution on Earth" class="wl">Earth's water</a>.<a href="#cite_note-Percentage-1" style="counter-reset: mw-Ref 1;">[1]</a> An ocean can also refer to any of the large bodies of water into which the world ocean is conventionally divided.<a href="#cite_note-:0-2" style="counter-reset: mw-Ref 2;">[2]</a> Separate names are used to identify five different areas of the ocean: <a href="/en/Pacific_Ocean" title="Pacific Ocean" class="wl">Pacific</a> (the largest), <a href="/en/Atlantic_Ocean" title="Atlantic Ocean" class="wl">Atlantic</a>, <a href="/en/Indian_Ocean" title="Indian Ocean" class="wl">Indian</a>, <a href="/en/Southern_Ocean" title="Southern Ocean" class="wl">Southern</a>, and <a href="/en/Arctic_Ocean" title="Arctic Ocean" class="wl">Arctic</a> (the smallest).<a href="#cite_note-oed.130201-3" style="counter-reset: mw-Ref 3;">[3]</a><a href="#cite_note-mw.ocean-4" style="counter-reset: mw-Ref 4;">[4]</a> <a href="/en/Seawater" title="Seawater" class="wl">Seawater</a> covers approximately 361,000,000&nbsp;km2 (139,000,000&nbsp;sq&nbsp;mi) of the planet. The ocean is the principal component of Earth's <a href="/en/Hydrosphere" title="Hydrosphere" class="wl">hydrosphere</a>, and therefore integral to <a href="/en/Life" title="Life" class="wl">life</a> on Earth. Acting as a huge <a href="/en/Ocean_heat_content" title="Ocean heat content" class="wl">heat reservoir</a>, the ocean influences <a href="/en/Climate" title="Climate" class="wl">climate</a> and <a href="/en/Weather" title="Weather" class="wl">weather</a> patterns, the <a href="/en/Carbon_cycle" title="Carbon cycle" class="wl">carbon cycle</a>, and the <a href="/en/Water_cycle" title="Water cycle" class="wl">water cycle</a>.

<div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none" about="#mwt1">Body of salt water covering the majority of Earth</div>
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<figure class="mw-default-size wiki-thumb"><a href="/en/File:World_map_ocean_locator-en.svg" class="mw-file-description image media-thumb" data-hash="File:World_map_ocean_locator-en.svg"><img loading="lazy" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6d/World_map_ocean_locator-en.svg/400px-World_map_ocean_locator-en.svg.png" decoding="async" data-file-width="1200" data-file-height="684" data-file-type="drawing" height="228" width="400" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6d/World_map_ocean_locator-en.svg/600px-World_map_ocean_locator-en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6d/World_map_ocean_locator-en.svg/800px-World_map_ocean_locator-en.svg.png 2x" alt="World_map_ocean_locator-en.svg"></a><figcaption>World map of the five-ocean model with approximate boundaries</figcaption></figure>
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.sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}</style><table class="sidebar nomobile nowraplinks plainlist" style="width:auto;"><tbody><tr><td class="sidebar-top-image notheme" style="background:#ddeffa;padding:0.5em 1.0em;"><a href="/en/File:Oceanus.png" class="mw-file-description image media-thumb" title="View of the Earth where all five oceans visible" data-hash="File:Oceanus.png"><img loading="lazy"alt="View of the Earth where all five oceans visible" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Oceanus.png/120px-Oceanus.png" decoding="async" data-file-width="407" data-file-height="407" data-file-type="bitmap" height="120" width="120" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Oceanus.png/180px-Oceanus.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Oceanus.png/240px-Oceanus.png 2x"></a></td></tr><tr><th class="sidebar-title">Earth's <a href="/en/Ocean" title="Ocean" class="wl">oceans</a></th></tr><tr><td class="sidebar-content">
<ul><li><a href="/en/Arctic_Ocean" title="Arctic Ocean" class="wl">Arctic</a></li>
<li><a href="/en/Atlantic_Ocean" title="Atlantic Ocean" class="wl">Atlantic</a></li>
<li><a href="/en/Indian_Ocean" title="Indian Ocean" class="wl">Indian</a></li>
<li><a href="/en/Pacific_Ocean" title="Pacific Ocean" class="wl">Pacific</a></li>
<li><a href="/en/Southern_Ocean" title="Southern Ocean" class="wl">Southern</a></li></ul></td>
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<a href="/en/Oceanography" title="Oceanography" class="wl">Oceanographers</a> divide the ocean into different vertical and horizontal zones based on physical and biological conditions. The <a href="/en/Pelagic_zone" title="Pelagic zone" class="wl">pelagic zone</a> consists of the <a href="/en/Water_column" title="Water column" class="wl">water column</a> from surface to ocean floor throughout the open ocean. The water column is further categorized in other zones depending on depth and on how much light is present. The <a href="/en/Photic_zone" title="Photic zone" class="wl">photic zone</a> includes water from the surface to a depth of 1% of the surface light (about 200&nbsp;m in the open ocean), where <a href="/en/Photosynthesis" title="Photosynthesis" class="wl">photosynthesis</a> can occur. This makes the photic zone the most <a href="/en/Biodiverse" title="Biodiverse" class="mw-redirect wl">biodiverse</a>. Photosynthesis by plants and microscopic <a href="/en/Algae" title="Algae" class="wl">algae</a> (free floating <a href="/en/Phytoplankton" title="Phytoplankton" class="wl">phytoplankton</a>) creates organic matter using light, water, carbon dioxide, and nutrients. Ocean photosynthesis creates 50% of the oxygen in earth's atmosphere.<a href="#cite_note-5" style="counter-reset: mw-Ref 5;">[5]</a> This upper sunlit zone is the origin of the food supply which sustains most of the ocean <a href="/en/Ecosystem" title="Ecosystem" class="wl">ecosystem</a>. Light penetrates to a depth of only a few hundred meters; the remaining ocean below is cold and dark. The <a href="/en/Continental_shelf" title="Continental shelf" class="wl">continental shelf</a> where the ocean approaches dry land is more shallow, with a depth of a few hundred meters or less. Human activity has a greater impact on the <a href="/en/Continental_shelf" title="Continental shelf" class="wl">continental shelf</a>.

<a href="/en/Ocean_temperature" title="Ocean temperature" class="wl">Ocean temperatures</a> depend on the amount of solar radiation reaching the ocean surface. In the tropics, <a href="/en/Sea_surface_temperature" title="Sea surface temperature" class="wl">surface temperatures</a> can rise to over 30&nbsp;°C (86&nbsp;°F). Near the poles where <a href="/en/Sea_ice" title="Sea ice" class="wl">sea ice</a> forms, the temperature in equilibrium is about −2&nbsp;°C (28&nbsp;°F). Deep ocean temperature is between −2&nbsp;°C (28&nbsp;°F) and 5&nbsp;°C (41&nbsp;°F) in all parts of the ocean.<a href="#cite_note-:7-6" style="counter-reset: mw-Ref 6;">[6]</a> Water continuously circulates in the oceans creating <a href="/en/Ocean_current" title="Ocean current" class="wl">ocean currents</a>. These directed movements of seawater are generated by forces acting upon the water, including temperature differences, <a href="/en/Atmospheric_circulation" title="Atmospheric circulation" class="wl">atmospheric circulation</a> (wind), the <a href="/en/Coriolis_effect" title="Coriolis effect" class="mw-redirect wl">Coriolis effect</a> and differences in <a href="/en/Salinity" title="Salinity" class="wl">salinity</a>.<a href="#cite_note-:8-7" style="counter-reset: mw-Ref 7;">[7]</a> Tidal currents originate from <a href="/en/Tide" title="Tide" class="wl">tides</a>, while surface currents are caused by wind and waves. Major ocean currents include the <a href="/en/Gulf_Stream" title="Gulf Stream" class="wl">Gulf Stream</a>, <a href="/en/Kuroshio_Current" title="Kuroshio Current" class="wl">Kuroshio Current</a>, <a href="/en/Agulhas_Current" title="Agulhas Current" class="wl">Agulhas Current</a> and <a href="/en/Antarctic_Circumpolar_Current" title="Antarctic Circumpolar Current" class="wl">Antarctic Circumpolar Current</a>. Collectively, currents move enormous amounts of water and heat around the globe. This circulation significantly impacts global climate and the uptake and redistribution of pollutants such as <a href="/en/Carbon_dioxide" title="Carbon dioxide" class="wl">carbon dioxide</a> by moving these contaminants from the surface into the deep ocean.

Ocean water contains large quantities of dissolved gases, including <a href="/en/Oxygen" title="Oxygen" class="wl">oxygen</a>, <a href="/en/Carbon_dioxide" title="Carbon dioxide" class="wl">carbon dioxide</a> and <a href="/en/Nitrogen" title="Nitrogen" class="wl">nitrogen</a>. This <a href="/en/Gas_exchange" title="Gas exchange" class="wl">gas exchange</a> takes place at the ocean surface and solubility depends on the temperature and salinity of the water.<a href="#cite_note-:9-8" style="counter-reset: mw-Ref 8;">[8]</a> The increasing concentration of <a href="/en/Carbon_dioxide_in_Earth's_atmosphere" title="Carbon dioxide in Earth's atmosphere" class="wl">carbon dioxide in the atmosphere</a> due to <a href="/en/Fossil_fuel" title="Fossil fuel" class="wl">fossil fuel</a> combustion leads to higher concentrations in ocean water, resulting in <a href="/en/Ocean_acidification" title="Ocean acidification" class="wl">ocean acidification</a>.<a href="#cite_note-:10-9" style="counter-reset: mw-Ref 9;">[9]</a> The ocean provides society with important <a href="/en/Ecosystem_service" title="Ecosystem service" class="wl">environmental services</a>, including climate regulation. It also offers a means of <a href="/en/Trade" title="Trade" class="wl">trade</a> and transport and access to food and other <a href="/en/Resource" title="Resource" class="wl">resources</a>. Known to be the <a href="/en/Habitat" title="Habitat" class="wl">habitat</a> of over 230,000 <a href="/en/Species" title="Species" class="wl">species</a>, it may contain far more – perhaps over two million species.<a href="#cite_note-la.2009-10" style="counter-reset: mw-Ref 10;">[10]</a> However, the ocean is subject to numerous human-caused <a href="/en/Environmental_issues" title="Environmental issues" class="wl">environmental</a> threats, including <a href="#Marine_pollution" target="_blank">marine pollution</a>, <a href="#Overfishing" target="_blank">overfishing</a>, and <a href="/en/Effects_of_climate_change_on_oceans" title="Effects of climate change on oceans" class="wl">effects of climate change on oceans</a>, such as <a href="/en/Ocean_heat_content" title="Ocean heat content" class="wl">ocean warming</a>, ocean acidification, <a href="/en/Sea_level_rise" title="Sea level rise" class="wl">sea level rise</a> and many more. The continental shelf and <a href="/en/Coast" title="Coast" class="wl">coastal waters</a> that are most influenced by human activity are especially vulnerable.

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The ocean is the body of salt water that covers approximately 70.8% of the Earth and contains 97% of Earth's water. Seawater covers approximately 361,000,000 km2 of the planet. The ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth. Acting as a huge heat reservoir, the ocean influences climate and weather patterns, the carbon cycle, and the water cycle. Oceanographers divide the ocean into different vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column from surface to ocean floor throughout the open ocean. The water column is further categorized in other zones depending on depth and on how much light is present. The photic zone includes water from the surface to a depth of 1% of the surface light , where photosynthesis can occur. This makes the photic zone the most biodiverse. Photosynthesis by plants and microscopic algae creates organic matter using light, water, carbon dioxide, and nutrients. Ocean photosynthesis creates 50% of the oxygen in earth's atmosphere. This upper sunlit zone is the origin of the food supply which sustains most of the ocean ecosystem. Light penetrates to a depth of only a few hundred meters; the remaining ocean below is cold and dark. The continental shelf where the ocean approaches dry land is more shallow, with a depth of a few hundred meters or less. Human activity has a greater impact on the continental shelf. 