Array ( [0] => {{Short description|Salt water covering most of Earth}} [1] => {{About|natural science aspects of Earth's oceans|more on human experience, history and culture of oceans|Sea|other uses|Ocean (disambiguation)}} [2] => {{pp-semi-indef}} [3] => {{Use mdy dates|date=April 2021}} [4] => {{Infobox body of water [5] => | name = Earth's ocean [6] => | image = Ocean world Earth.jpg [7] => | caption = [[Pacific Ocean]] side, [[Apollo 11]], July 1969 [8] => | alt = [9] => | image_bathymetry = [10] => | basin_countries = [[List of countries by length of coastline]] [11] => | area = {{cvt|361000000|km2|0}}
(71% Earth's surface area) [12] => | depth = {{cvt|3.688|km|0}}{{cite web |title=How deep is the ocean? |website=NOAA's National Ocean Service |url=https://oceanservice.noaa.gov/facts/oceandepth.html#:~:text=The%20average%20depth%20of%20the,U.S.%20territorial%20island%20of%20Guam. |access-date=2023-05-10}} [13] => | max-depth = {{cvt|11.034|km|3}}
[14] => ([[Challenger Deep]]){{cite web |url=http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html |title=Challenger Deep – the Mariana Trench |access-date=30 July 2012 |archive-date=24 April 2006 |archive-url=https://web.archive.org/web/20060424000302/http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html |url-status=dead }} [15] => | volume = {{cvt|1370000000|km3|0}}{{cite journal |last=Webb |first=Paul |title=1.1 Overview of the Oceans |website=Roger Williams University Open Publishing – Driving learning and savings, simultaneously. |url=https://rwu.pressbooks.pub/webboceanography/chapter/1-1-overview-of-the-oceans/ |access-date=2023-05-10}} (97.5% of Earth's water) [16] => | temperature_high = {{unbulleted list [17] => |{{cvt|30|C}} (max. surface) [18] => |{{cvt|20|C}} (avg. surface) [19] => |{{cvt|4|C}} (avg. overall){{cite web |title=Voyager: How Long until Ocean Temperature Goes up a Few More Degrees? |website=Scripps Institution of Oceanography |date=2014-03-18 |url=https://scripps.ucsd.edu/news/voyager-how-long-until-ocean-temperature-goes-few-more-degrees |access-date=2023-05-10}} [20] => }} [21] => | temperature_low = {{unbulleted list [22] => | {{cvt|-2|C}} (surface) [23] => | {{cvt|1|C}} (deepest points){{cite web |title=How does the temperature of ocean water vary? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research |website=Home |date=2013-03-05 |url=https://oceanexplorer.noaa.gov/facts/temp-vary.html |access-date=2023-05-10}} [24] => }} [25] => | shore = Low interval calculation: {{cvt|356,000|km|0}}{{Cite web |url=https://www.cia.gov/the-world-factbook/field/coastline |title=Coastline – The World Factbook |website=Central Intelligence Agency }} [26] => High interval calculation: {{cvt|1,634,701|km}}{{cite web |url=http://earthtrends.wri.org/text/coastal-marine/variable-61.html |title=Coastal and Marine Ecosystems – Marine Jurisdictions: Coastline length |work=[[World Resources Institute]] |access-date=2012-03-18 |archive-url=https://web.archive.org/web/20120419075053/http://earthtrends.wri.org/text/coastal-marine/variable-61.html |archive-date=2012-04-19}}{{vague|date=December 2023}} [27] => | sections = [[Borders of the oceans|Main divisions]] (volume %): [28] => {{unbulleted list [29] => | [[Pacific Ocean]] (50.1%) [30] => | [[Atlantic Ocean]] (23.3%) [31] => | [[Indian Ocean]] (19.8%) [32] => | [[Southern Ocean|Antarctic/Southern Ocean]] (5.4%) [33] => | [[Arctic Ocean]] (1.4%) [34] => }} [35] => Other divisions: [[Marginal seas]] [36] => | trenches = [[List of oceanic trenches]] [37] => }} [38] => [39] => The '''ocean''' is the body of [[Saline water|salt water]] that covers ~70.8% of the [[Earth]]. In [[English language|English]], the term ''ocean'' also refers to any of the large bodies of water into which the world ocean is conventionally divided.[https://www.merriam-webster.com/dictionary/ocean?src=search-dict-box#synonyms "Ocean."] ''Merriam-Webster.com Dictionary'', Merriam-Webster, https://www.merriam-webster.com/dictionary/ocean . Accessed March 14, 2021. Distinct names are used to identify five different areas of the ocean: [[Pacific Ocean|Pacific]], [[Atlantic Ocean|Atlantic]], [[Indian Ocean|Indian]], [[Southern Ocean|Antarctic/Southern]], and [[Arctic Ocean|Arctic]].{{cite web |url=http://www.oed.com/view/Entry/130201?redirectedFrom=ocean#eid |title=ocean, n |publisher=Oxford English Dictionary |access-date=February 5, 2012}}{{cite web |url=http://www.merriam-webster.com/dictionary/ocean |title=ocean |publisher=Merriam-Webster |access-date=February 6, 2012}} The ocean contains 97% of [[Water distribution on Earth|Earth's water]] and is the primary component of the Earth's [[hydrosphere]], thus the ocean is essential to [[life]] on Earth. The ocean influences [[climate]] and [[weather]] patterns, the [[carbon cycle]], and the [[water cycle]] by acting as a huge [[Ocean heat content|heat reservoir]]. [40] => [41] => [[Oceanography|Oceanographers]] split the ocean into vertical and horizontal zones based on physical and biological conditions. The [[pelagic zone]] is the open ocean's [[water column]] from the surface to the ocean floor. The water column is further divided into zones based on depth and the amount of light present. The [[photic zone]] starts at the surface and is defined to be "the depth at which light intensity is only 1% of the surface value"{{rp|36}} (approximately 200 m in the open ocean). This is the zone where [[photosynthesis]] can occur. In this process plants and microscopic [[algae]] (free floating [[phytoplankton]]) use light, water, carbon dioxide, and nutrients to produce organic matter. As a result, the photic zone is the most [[biodiverse]] and the source of the food supply which sustains most of the ocean [[ecosystem]]. Ocean photosynthesis also produces half of the oxygen in the Earth's atmosphere.{{cite web |title=How much oxygen comes from the ocean? |url=https://oceanservice.noaa.gov/facts/ocean-oxygen.html |publisher=National Ocean Service. National Oceanic and Atmospheric Administration U.S. Department of Commerce |access-date=3 November 2021 |date=26 February 2021}} Light can only penetrate a few hundred more meters; the rest of the deeper ocean is cold and dark (these zones are called [[Mesopelagic zone|mesopelagic]] and [[Aphotic zone|aphotic]] zones). The [[continental shelf]] is where the ocean meets dry land. It is more shallow, with a depth of a few hundred meters or less. Human activity often has [[Human impact on marine life|negative impacts]] on the ecosystems within the continental shelf. [42] => [43] => [[Ocean temperature]]s depend on the amount of solar radiation reaching the ocean surface. In the tropics, [[Sea surface temperature|surface temperatures]] can rise to over {{convert|30|°C}}. Near the poles where [[sea ice]] forms, the temperature in equilibrium is about {{convert|-2|°C}}. In all parts of the ocean, deep ocean temperatures range between {{convert|-2|°C}} and {{convert|5|°C}}. Constant circulation of water in the ocean creates [[ocean current]]s. These directed movements of seawater are caused by forces operating on the water, such as temperature variations, [[atmospheric circulation]] (wind), the [[Coriolis effect]] and [[salinity]] changes. [[Tide]]s create tidal currents, while wind and waves cause surface currents. The [[Gulf Stream]], [[Kuroshio Current]], [[Agulhas Current]] and [[Antarctic Circumpolar Current]] are all major ocean currents. Currents transport massive amounts of water and heat around the world. By transporting these pollutants from the surface into the deep ocean, this circulation impacts global climate and the uptake and redistribution of pollutants such as [[carbon dioxide]]. [44] => [45] => Ocean water contains a high concentration of dissolved gases, including [[oxygen]], [[carbon dioxide]] and [[nitrogen]]. This [[gas exchange]] occurs at the ocean's surface and solubility depends on the temperature and salinity of the water. [[Carbon dioxide in Earth's atmosphere|Carbon dioxide concentration in the atmosphere]] rises due to [[fossil fuel]] combustion, which causes higher levels in ocean water, resulting in [[ocean acidification]].IUCN (2017) [https://web.archive.org/web/20210725133055/https://www.iucn.org/sites/dev/files/the_ocean_and_climate_change_issues_brief-v2.pdf The Ocean and Climate Change ], IUCN (International Union for Conservation of Nature) Issues Brief. The ocean provides crucial [[Ecosystem service|environmental services]] to humankind, such as climate regulation. It also provides a means of [[trade]] and transport as well as access to food and other [[resource]]s. It is known to be the [[habitat]] of over 230,000 [[species]], but may hold considerably more – perhaps over two million species.{{cite news |last=Drogin |first=Bob |date=August 2, 2009 |title=Mapping an ocean of species |work=Los Angeles Times |url=http://articles.latimes.com/2009/aug/02/nation/na-fish2 |access-date=August 18, 2009}} However, the ocean faces numerous human-caused [[environmental issues|environmental]] threats, such as [[#Marine pollution|marine pollution]], [[#Overfishing|overfishing]], and [[effects of climate change on oceans]] such as [[Ocean heat content|ocean warming]], ocean acidification and [[sea level rise]]. The [[continental shelf]] and [[Coast|coastal waters]] that are most affected by human activity are particularly vulnerable. [46] => [47] => {{TOC limit|3}} [48] => [49] => ==Terminology== [50] => ===Ocean and sea=== [51] => The terms "the ocean" or "the sea" used without specification refer to the interconnected body of salt water covering the majority of the Earth's surface. It includes the [[Atlantic Ocean|Atlantic]], [[Pacific Ocean|Pacific]], [[Indian Ocean|Indian]], [[Southern Ocean|Antarctic/Southern]] and [[Arctic Ocean]]s.{{cite web |title=Sea |url=http://www.merriam-webster.com/dictionary/sea |access-date=March 13, 2013 |publisher=Merriam-webster.com}} As a general term, "the ocean" and "the sea" are often [[interchangeable]], although speakers of [[British English]] refer to "the sea" in all cases,Bromhead, Helen, [https://books.google.com/books?id=L4JvDwAAQBAJ&pg=PA92 ''Landscape and Culture – Cross-linguistic Perspectives''], p. 92, John Benjamins Publishing Company, 2018, {{ISBN|978-9027264008}}; unlike Americans, speakers of [[British English]] do not go swimming in "the ocean" but always "the sea".{{dubious |reason=The source seems to be specifically referring to use of these terms in the context of the act of swimming, and not in "all cases". |date=June 2023}} even when the body of water is one of the oceans. [52] => [53] => Strictly speaking, a "sea" is a body of water (generally a division of the world ocean) partly or fully enclosed by land.{{cite web |title=WordNet Search – sea |url=http://wordnetweb.princeton.edu/perl/webwn?s=sea |access-date=February 21, 2012 |publisher=Princeton University}} The word "sea" can also be used for many specific, much smaller bodies of seawater, such as the [[North Sea]] or the [[Red Sea]]. There is no sharp distinction between seas and oceans, though generally seas are smaller, and are often partly (as [[marginal sea]]s) or wholly (as [[Inland sea (geology)|inland seas]]) bordered by land.{{cite web |title=What's the difference between an ocean and a sea?|url=http://oceanservice.noaa.gov/facts/oceanorsea.html |access-date=April 19, 2013 |work=Ocean facts |publisher=National Oceanic and Atmospheric Administration}} [54] => [55] => ===World ocean=== [56] => {{redirect-distinguish|World Ocean|Ocean World (disambiguation){{!}}Ocean World}} [57] => The contemporary concept of the ''World Ocean'' was coined in the early 20th century by the [[Russian Empire|Russian]] oceanographer [[Yuly Shokalsky]] to refer to the continuous ocean that covers and encircles most of the Earth.{{cite book |last1=Janin |first1=H. |last2=Mandia |first2=S.A. |title=Rising Sea Levels: An Introduction to Cause and Impact |publisher=McFarland, Incorporated, Publishers |year=2012 |isbn=978-0-7864-5956-8 |url=https://books.google.com/books?id=it27LP5V0ugC&pg=PA20 |access-date=2022-08-26 |page=20}}{{cite book |author=Bruckner, Lynne and Dan Brayton|url=https://archive.org/details/ecocriticalshake0000bruc |title=Ecocritical Shakespeare (Literary and Scientific Cultures of Early Modernity) |publisher=Ashgate Publishing, Ltd |year=2011 |isbn=978-0754669197 |url-access=registration}} The global, interconnected body of salt water is sometimes referred to as the World Ocean, ''global ocean'' or ''the great ocean''.{{cite web |last=Ro |first=Christine |title=Is It Ocean Or Oceans? |website=Forbes |date=2020-02-03 |url=https://www.forbes.com/sites/christinero/2020/02/03/is-it-ocean-or-oceans/ |access-date=2022-08-26}}{{cite web |title=Ocean |url=https://www.sciencedaily.com/articles/o/ocean.htm |access-date=November 8, 2012 |publisher=Sciencedaily.com |archive-date=April 24, 2015 |archive-url=https://web.archive.org/web/20150424155934/http://www.sciencedaily.com/articles/o/ocean.htm |url-status=dead}}"{{cite web |title=Distribution of land and water on the planet |url=http://www.oceansatlas.org/unatlas/about/physicalandchemicalproperties/background/seemore1.html |url-status=dead |archive-url=https://web.archive.org/web/20160303234925/http://www.oceansatlas.org/unatlas/about/physicalandchemicalproperties/background/seemore1.html |archive-date=March 3, 2016 |work=UN Atlas of the Oceans}} The concept of a continuous body of water with relatively unrestricted exchange between its components is critical in [[oceanography]].{{cite journal |last=Spilhaus |first=Athelstan F. |date=July 1942 |title=Maps of the whole world ocean |journal=Geographical Review |volume=32 |issue=3 |pages=431–435 |doi=10.2307/210385 |jstor=210385|bibcode=1942GeoRv..32..431S }} [58] => [59] => ===Etymology=== [60] => The word ''ocean'' comes from the figure in [[classical antiquity]], [[Oceanus]] ({{IPAc-en|oʊ|ˈ|s|iː|ə|n|ə|s|}}; {{lang-grc-gre|{{linktext|Ὠκεανός}}}} ''Ōkeanós'',[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D*%29wkeano%2Fs Ὠκεανός], Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', at Perseus project {{IPA-el|ɔːkeanós|pron}}), the elder of the [[Titan (mythology)|Titans]] in classical [[Greek mythology]]. Oceanus was believed by the [[Ancient Greece|ancient Greeks]] and [[Ancient Rome|Romans]] to be the divine personification of an enormous [[river]] encircling the world. [61] => [62] => The concept of Ōkeanós has an [[Indo-European religion|Indo-European]] connection. Greek Ōkeanós has been compared to the [[Vedic]] epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases.[[Ranko Matasović|Matasović, Ranko]], [http://mudrac.ffzg.unizg.hr/~rmatasov/PIE%20Religion.pdf A Reader in Comparative Indo-European Religion] Zagreb: Univ of Zagreb, 2016. page 20. [63] => [64] => ==Natural history== [65] => {{Further|List of ancient oceans}} [66] => [67] => ===Origin of water=== [68] => {{Further|Origin of water on Earth}} [69] => [70] => Scientists believe that a sizable quantity of [[water]] would have been in the material that formed Earth.{{Citation|last=Drake|first=Michael J.|title=Origin of water in the terrestrial planets|journal=Meteoritics & Planetary Science|volume=40|issue=4|pages=515–656|year=2005|bibcode=2005M&PS...40..515J|doi=10.1111/j.1945-5100.2005.tb00958.x|s2cid=247695232 |doi-access=}}. Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. This is called [[atmospheric escape]]. [71] => [72] => During [[Earth#Formation|planetary formation]], Earth possibly had [[magma ocean]]s. Subsequently, [[outgassing]], [[volcanism|volcanic activity]] and [[meteorite impact]]s, produced an early atmosphere of [[carbon dioxide]], [[nitrogen]] and [[water vapor]], according to current theories. [73] => The gases and the atmosphere are thought to have accumulated over millions of years. After Earth's surface had significantly cooled, the [[water vapor]] over time would have condensed, forming Earth's first oceans.{{cite web |title=Why do we have an ocean? |website=NOAA's National Ocean Service |date=2013-06-01 |url=https://oceanservice.noaa.gov/facts/why_oceans.html |access-date=2022-09-03}} The early oceans might have been significantly hotter than today and appeared green due to high iron content.{{cite web |title=NASA Astrobiology |website=Astrobiology |date=2017-06-05 |url=https://astrobiology.nasa.gov/news/how-hot-were-the-oceans-when-life-first-evolved/ |access-date=2022-09-13}} [74] => [75] => Geological evidence helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption) was recovered from the [[Isua Greenstone Belt]] and provides evidence that water existed on Earth 3.8 billion years ago.{{Citation|last1=Pinti|first1=Daniele L.|title=Oceans, Origin of|date=2014|encyclopedia=Encyclopedia of Astrobiology|pages=1–5|publisher=Springer Berlin Heidelberg|isbn=978-3642278334|last2=Arndt|first2=Nicholas|doi=10.1007/978-3-642-27833-4_1098-4}} In the [[Nuvvuagittuq Greenstone Belt]], Quebec, Canada, rocks dated at 3.8 billion years old by one study{{Cite journal|last1=Cates|first1=N.L.|last2=Mojzsis|first2=S.J.|date=March 2007|title=Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq supracrustal belt, northern Québec|journal=Earth and Planetary Science Letters|volume=255|issue=1–2|pages=9–21|doi=10.1016/j.epsl.2006.11.034|issn=0012-821X|bibcode=2007E&PSL.255....9C}} and 4.28 billion years old by another{{Cite journal|last1=O'Neil|first1=Jonathan|last2=Carlson|first2=Richard W.|last3=Paquette|first3=Jean-Louis|last4=Francis|first4=Don|date=November 2012|title=Formation age and metamorphic history of the Nuvvuagittuq Greenstone Belt|journal=Precambrian Research|volume=220–221|pages=23–44|doi=10.1016/j.precamres.2012.07.009|issn=0301-9268|bibcode=2012PreR..220...23O|s2cid=128825728 |url=https://hal.archives-ouvertes.fr/hal-00793868/file/O%27Neil2012.pdf }} show evidence of the presence of water at these ages. If oceans existed earlier than this, any geological evidence either has yet to be discovered, or has since been destroyed by geological processes like [[crustal recycling]]. [76] => However, in August 2020, researchers reported that sufficient water to fill the oceans may have always been on the [[Earth]] since the beginning of the planet's formation.{{cite news |author=Washington University in St. Louis |author-link=Washington University in St. Louis |date=27 August 2020 |title=Meteorite study suggests Earth may have been wet since it formed – Enstatite chondrite meteorites, once considered 'dry,' contain enough water to fill the oceans – and then some |work=[[EurekAlert!]] |url=https://www.eurekalert.org/pub_releases/2020-08/wuis-mss082620.php |access-date=28 August 2020}}{{cite news |author=American Association for the Advancement of Science |title=Unexpected abundance of hydrogen in meteorites reveals the origin of Earth's water |url=https://www.eurekalert.org/pub_releases/2020-08/aaft-uao082420.php |date=27 August 2020 |work=[[EurekAlert!]] |access-date=28 August 2020 }}{{Cite journal|last1=Piani|first1=Laurette|last2=Marrocchi|first2=Yves|last3=Rigaudier|first3=Thomas|last4=Vacher|first4=Lionel G.|last5=Thomassin|first5=Dorian|last6=Marty|first6=Bernard|date=2020|title=Earth's water may have been inherited from material similar to enstatite chondrite meteorites|url=https://doi.org/10.1126/science.aba1948|journal=Science|language=en|volume=369|issue=6507|pages=1110–1113|doi=10.1126/science.aba1948|issn=0036-8075|pmid=32855337|bibcode=2020Sci...369.1110P|s2cid=221342529}} In this model, atmospheric [[greenhouse gas]]es kept the oceans from freezing when the newly forming [[Sun]] had [[Faint young Sun paradox|only 70%]] of its [[solar luminosity|current luminosity]].{{cite conference |last1=Guinan |first1=E. F. |last2=Ribas |first2=I. |editor=Benjamin Montesinos, Alvaro Gimenez and Edward F. Guinan |title=Our Changing Sun: The Role of Solar Nuclear Evolution and Magnetic Activity on Earth's Atmosphere and Climate |work=ASP Conference Proceedings: The Evolving Sun and its Influence on Planetary Environments |year=2002 |location=San Francisco |isbn=978-1-58381-109-2 |publisher=Astronomical Society of the Pacific |bibcode=2002ASPC..269...85G}} [77] => [78] => ===Ocean formation=== [79] => {{Main|Paleoceanography}}The origin of Earth's oceans is unknown. Oceans are thought to have formed in the [[Hadean]] eon and may have been the cause for the [[Abiogenesis|emergence of life]]. [80] => [81] => [[Plate tectonics]], [[post-glacial rebound]], and [[sea level rise]] continually change the [[coast]]line and structure of the world ocean. A global ocean has existed in one form or another on Earth for eons. [82] => [83] => Since its formation the ocean has taken many conditions and shapes with many [[List of ancient oceans|past ocean divisions]] and potentially at times covering the whole globe. [84] => [85] => During colder climatic periods, more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age, glaciers covered almost one-third of Earth's land mass with the result being that the oceans were about 122 m (400 ft) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 5.5 m (18 ft) higher than they are now. About three million years ago the oceans could have been up to 50 m (165 ft) higher.{{Cite web |title=The Water Cycle summary |url=https://water.usgs.gov/edu/watercyclesummary.html |url-status=live |archive-url=https://web.archive.org/web/20180116135448/https://water.usgs.gov/edu/watercyclesummary.html |archive-date=2018-01-16 |access-date=2018-01-15 |website=USGS Water Science School}} [86] => [87] => ==Geography== [88] => {{Further|Water distribution on Earth}} [89] => [[File:World map ocean locator-en.svg|upright=1.8|thumb|World map of the five-ocean model with approximate boundaries]] [90] => The entire ocean, containing 97% of Earth's water, spans 70.8% of [[Earth]]'s surface,{{Cite web|url=http://www.physicalgeography.net/fundamentals/8o.html|title=8(o) Introduction to the Oceans|website=www.physicalgeography.net}} making it Earth's global ocean or ''world ocean''. This makes Earth, along with its vibrant [[hydrosphere]] a "water world"{{cite web |last=Smith |first=Yvette |title=Earth Is a Water World |website=NASA |date=2021-06-07 |url=http://www.nasa.gov/image-feature/earth-is-a-water-world |access-date=2022-08-27}}{{cite web | title=Water-Worlds | website=National Geographic Society | date=2022-05-20 | url=https://education.nationalgeographic.org/resource/water-worlds/ | access-date=2022-08-24}} or "[[ocean world]]",{{cite journal | last=Lunine | first=Jonathan I. | title=Ocean worlds exploration | journal=Acta Astronautica | publisher=Elsevier BV | volume=131 | year=2017 | issn=0094-5765 | doi=10.1016/j.actaastro.2016.11.017 | pages=123–130| bibcode=2017AcAau.131..123L | doi-access=free }}{{cite web | title=Ocean Worlds | website=Ocean Worlds | url=http://www.nasa.gov/specials/ocean-worlds/index.html | access-date=2022-08-27 | archive-date=August 27, 2022 | archive-url=https://web.archive.org/web/20220827003111/https://www.nasa.gov/specials/ocean-worlds/index.html | url-status=dead }} particularly in Earth's early history when the ocean is thought to have possibly covered Earth completely.{{cite journal | last=Voosen | first=Paul | title=Ancient Earth was a water world | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | date=March 9, 2021 | volume=371 | issue=6534 | pages=1088–1089 | issn=0036-8075 | doi=10.1126/science.abh4289 | pmid=33707245 | s2cid=241687784 }} The ocean's shape is irregular, unevenly dominating the [[Earth's surface]]. This leads to the distinction of the Earth's surface into a [[water hemisphere|water and land hemisphere]], as well as the division of the ocean into different oceans. [91] => [92] => [[Seawater]] covers about {{convert|361,000,000|km2|abbr=on}} and the ocean's furthest [[pole of inaccessibility]], known as "[[Point Nemo]]", in a region known as [[spacecraft cemetery]] of the [[South Pacific Ocean]], at {{Coord|48|52.6|S|123|23.6|W|type:landmark|name=Point Nemo}}. This point is roughly {{cvt|2688|km|0}} from the nearest land.{{cite web |url=http://oceanservice.noaa.gov/facts/nemo.html |title=Where is Point Nemo? |work=NOAA |access-date=20 February 2015}} [93] => [94] => [95] => ===Oceanic divisions=== [96] => {{Further|Borders of the oceans}} [97] => [[File:World_ocean_map.gif|thumb|220x220px|Map of Earth centered on its ocean, showing the different ocean divisions]] [98] => There are different customs to subdivide the ocean and are adjourned by smaller bodies of water such as, [[List of seas|seas]], [[List of gulfs|gulfs]], [[bay]]s, [[Bight (geography)|bights]], and [[strait]]s. [99] => [100] => The ocean is customarily divided into five principal oceans – listed below in descending order of area and volume: [101] => {| class="wikitable sortable" style="text-align:right;" [102] => |+Oceans by size [103] => |- [104] => !scope="col" class="unsortable"| # [105] => !scope="col"| Ocean [106] => !scope="col" class="unsortable"| Location [107] => !scope="col"| Area
(km2) [108] => !scope="col"| Volume
(km3) [109] => !scope="col"| Avg. depth
(m) [110] => !scope="col"| Coastline
(km) [111] => |-style="vertical-align:text-top;" [112] => !scope="row"| 1 [113] => | style="text-align:left;"| [[Pacific Ocean]] || align=left | Between [[Asia]] and [[Australasia]] and the [[Americas]] || {{nts|168723000}}
''(46.6%)'' || {{nts|669880000}}
''(50.1%)'' || {{nts|3970}} || {{nts|135663}}
''(35.9%)'' [114] => |-style="vertical-align:text-top;" [115] => !scope="row"| 2 [116] => | align=left | [[Atlantic Ocean]] || align=left | Between the [[Americas]] and [[Europe]] and [[Africa]] || {{nts|85133000}}
''(23.5%)'' || {{nts|310410900}}
''(23.3%)'' || {{nts|3646}} || {{nts|111866}}
''(29.6%)'' [117] => |-style="vertical-align:text-top;" [118] => !scope="row"| 3 [119] => | align=left | [[Indian Ocean]] || align=left | Between [[Indian subcontinent|southern Asia]], [[Africa]] and [[Australia (continent)|Australia]] || {{nts|70560000}}
''(19.5%)'' || {{nts|264000000}}
''(19.8%)'' || {{nts|3741}} || {{nts|66526}}
''(17.6%)'' [120] => |-style="vertical-align:text-top;" [121] => !scope="row"| 4 [122] => | align=left | [[Southern Ocean|Antarctic/Southern Ocean]] || align=left | Between [[Antarctica]] and the Pacific, Atlantic and Indian oceans
''Sometimes considered an extension of those three oceans.''|| {{nts|21960000}}
''(6.1%)'' || {{nts|71800000}}
''(5.4%)'' || {{nts|3270}} || {{nts|17968}}
''(4.8%)'' [123] => |-style="vertical-align:text-top;" [124] => !scope="row"| 5 [125] => | align=left | [[Arctic Ocean]] || align=left | Between northern [[North America]] and [[Eurasia]] in the [[Arctic]]
''Sometimes considered a [[marginal sea]] of the Atlantic.'' || {{nts|15558000}}
''(4.3%)'' || {{nts|18750000}}
''(1.4%)'' || {{nts|1205}} || {{nts|45389}}
''(12.0%)'' [126] => |- class="sortbottom" style="font-weight:bold;vertical-align:text-top;" [127] => ! colspan="3" | Total [128] => ! {{nts|361900000}}
''(100%)'' [129] => ! {{nts|1335000000}}
''(100%)'' [130] => ! {{nts|3688}} [131] => ! {{nts|377412}}
''(100%)'' [132] => |} [133] => {{longitem|'''NB:''' Volume, area, and average depth figures include [[National Oceanic and Atmospheric Administration|NOAA]] ETOPO1 figures for marginal [[South China Sea]].
Sources: ''[[Encyclopedia of Earth]]'',{{cite web |title=Pacific Ocean |url=http://www.eoearth.org/view/article/155111/ |website=[[Encyclopedia of Earth]] |access-date=March 7, 2015}}{{cite web|title=Atlantic Ocean |url=http://www.eoearth.org/view/article/51cbecfc7896bb431f68ef68/ |website=Encyclopedia of Earth |access-date=March 7, 2015}}{{cite web |title=Indian Ocean |url=http://www.eoearth.org/view/article/51cbee377896bb431f6962fa/ |website=Encyclopedia of Earth |access-date=March 7, 2015}}{{cite web |title=Southern Ocean |url=http://www.eoearth.org/view/article/51cbeeee7896bb431f69b419/ |website=Encyclopedia of Earth |access-date=March 10, 2015}}{{cite web |title=Arctic Ocean |url=http://www.eoearth.org/view/article/150195/ |website=Encyclopedia of Earth |access-date=March 7, 2015}} [[International Hydrographic Organization]],{{cite web |url=https://iho.int/uploads/user/pubs/standards/s-23/S-23_Ed3_1953_EN.pdf |title=Limits of Oceans and Seas, 3rd edition |year=1953 |publisher=International Hydrographic Organization |access-date=December 28, 2020 |archive-url=https://web.archive.org/web/20111008191433/http://www.iho.int/iho_pubs/standard/S-23/S-23_Ed3_1953_EN.pdf |archive-date=October 8, 2011}} ''Regional Oceanography: an Introduction'' (Tomczak, 2005),{{cite book [134] => | first1=Matthias [135] => | last1=Tomczak [136] => | first2=J. Stuart [137] => | last2=Godfrey [138] => | title=Regional Oceanography: an Introduction [139] => | edition=2 [140] => | year=2003 [141] => | publisher=Daya Publishing House [142] => | place=Delhi [143] => | isbn=978-81-7035-306-5 [144] => | url=http://www.es.flinders.edu.au/~mattom/regoc/ [145] => | access-date=April 10, 2006 [146] => | archive-url=https://web.archive.org/web/20070630202249/http://www.es.flinders.edu.au/~mattom/regoc/ [147] => | archive-date=June 30, 2007 [148] => | url-status=dead [149] => }} ''[[Encyclopædia Britannica]]'',{{Cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/33188/Arctic-Ocean/57838/Oceanography |last=Ostenso |first=Ned Allen |title=Arctic Ocean |encyclopedia=Encyclopædia Britannica |access-date=July 2, 2012 |quote=As an approximation, the Arctic Ocean may be regarded as an estuary of the Atlantic Ocean.}} and the [[International Telecommunication Union]].{{cite web |title=Recommendation ITU-R RS.1624: Sharing between the Earth exploration-satellite (passive) and airborne altimeters in the aeronautical radionavigation service in the band 4 200–4 400 MHz (Question ITU-R 229/7) |url=https://www.itu.int/dms_pubrec/itu-r/rec/rs/R-REC-RS.1624-0-200305-I!!PDF-E.pdf |publisher=[[International Telecommunication Union|ITU Radiotelecommunication Sector (ITU-R)]] |access-date=April 5, 2015 |quote=The oceans occupy about 3.35×108 km2 of area. There are 377412 km of oceanic coastlines in the world.}}|style=line-height:1.4em; margin:.2em 0 1.4em 1em; font-size: 0.9em;}} [150] => [151] => ===Ocean basins=== [152] => {{Further|List of submarine topographical features}} [153] => [[File:Mid-ocean ridge system.gif|thumb|upright=1.7| {{center|[[Bathymetry]] of the ocean floor showing the [[continental shelf|continental shelves]] and [[oceanic plateau]]s (red), the [[mid-ocean ridge]]s (yellow-green) and the [[abyssal plain]]s (blue to purple)}}]] [154] => [155] => The ocean fills Earth's [[oceanic basin]]s. Earth's oceanic basins cover different [[geologic province]]s of Earth's [[oceanic crust]] as well as [[continental crust]]. As such it covers mainly Earth's [[structural basin]]s, but also [[continental shelf]]s. [156] => [157] => In mid-ocean, [[magma]] is constantly being thrust through the seabed between adjoining plates to form [[mid-oceanic ridge]]s and here convection currents within the mantle tend to drive the two plates apart. Parallel to these ridges and nearer the coasts, one oceanic plate may slide beneath another oceanic plate in a process known as [[subduction]]. Deep [[Oceanic trench|trenches]] are formed here and the process is accompanied by friction as the plates grind together. The movement proceeds in jerks which cause earthquakes, heat is produced and [[magma]] is forced up creating underwater mountains, some of which may form chains of volcanic islands near to deep trenches. Near some of the boundaries between the land and sea, the slightly denser oceanic plates slide beneath the continental plates and more subduction trenches are formed. As they grate together, the continental plates are deformed and buckle causing mountain building and seismic activity.{{cite encyclopedia |title=Plate tectonics |encyclopedia=The Encyclopedia of Earth |url=http://www.eoearth.org/view/article/155264/ |access-date=20 September 2013 |date=28 March 2013 |archive-url=https://web.archive.org/web/20141021013954/http://www.eoearth.org/view/article/155264/ |archive-date=21 October 2014 |author=Pidwirny, Michael |url-status=live}}{{cite web |title=Plate Tectonics: The Mechanism |url=http://www.ucmp.berkeley.edu/geology/tectonics.html |url-status=live |archive-url=https://web.archive.org/web/20140730190214/http://www.ucmp.berkeley.edu/geology/tectonics.html |archive-date=30 July 2014 |access-date=20 September 2013 |publisher=University of California Museum of Paleontology}} [158] => [159] => Every ocean basin has a [[mid-ocean ridge]], which creates a long mountain range beneath the ocean. Together they form the global mid-oceanic ridge system that features the [[List of mountain ranges#By length|longest]] [[mountain range]] in the world. The longest continuous mountain range is {{convert|65000|km|mi|abbr=on}}. This underwater mountain range is several times longer than the longest continental mountain range{{snd}}the [[Andes]].{{cite web|title=What is the longest mountain range on earth? |url=http://oceanservice.noaa.gov/facts/midoceanridge.html |website=National Ocean Service |publisher=US Department of Commerce |access-date=October 17, 2014}} [160] => [161] => [[Oceanography|Oceanographers]] state that less than 20% of the oceans have been mapped.{{cite web|title=NOAA – National Oceanic and Atmospheric Administration – Ocean|url=https://oceanservice.noaa.gov/facts/exploration.html|access-date=February 16, 2020|publisher=Noaa.gov}}{{Vague|date={{CURRENTMONTHNAME}} {{CURRENTYEAR}}}} [162] => [163] => === Interaction with the coast === [164] => {{Main|Coast}} [165] => [[File:Praia_da_Marinha_2017.jpg|thumb|[[Praia da Marinha]] in [[Algarve]], Portugal]] [166] => The zone where land meets sea is known as the [[coast]] and the part between the lowest spring tides and the upper limit reached by splashing waves is the [[shore]]. A [[beach]] is the accumulation of sand or [[Shingle beach|shingle]] on the shore.{{cite book |last=Monkhouse |first=F. J. |title=Principles of Physical Geography |publisher=Hodder & Stoughton |year=1975 |isbn=978-0-340-04944-0 |pages=280–291}} A [[headland]] is a point of land jutting out into the sea and a larger [[promontory]] is known as a [[Cape (geography)|cape]]. The indentation of a coastline, especially between two headlands, is a [[bay]], a small bay with a narrow inlet is a [[cove]] and a large bay may be referred to as a [[List of gulfs|gulf]].{{cite book |last=Whittow |first=John B. |title=The Penguin Dictionary of Physical Geography |publisher=Penguin Books |year=1984 |isbn=978-0-14-051094-2 |pages=29, 80, 246}} Coastlines are influenced by several factors including the strength of the waves arriving on the shore, the gradient of the land margin, the composition and hardness of the coastal rock, the inclination of the off-shore slope and the changes of the level of the land due to local uplift or submergence. [167] => [168] => Normally, waves roll towards the shore at the rate of six to eight per minute and these are known as constructive waves as they tend to move material up the beach and have little erosive effect. Storm waves arrive on shore in rapid succession and are known as destructive waves as the [[swash]] moves beach material seawards. Under their influence, the sand and shingle on the beach is ground together and abraded. Around high tide, the power of a storm wave impacting on the foot of a cliff has a shattering effect as air in cracks and crevices is compressed and then expands rapidly with release of pressure. At the same time, sand and pebbles have an erosive effect as they are thrown against the rocks. This tends to undercut the cliff, and normal [[weathering]] processes such as the action of frost follows, causing further destruction. Gradually, a wave-cut platform develops at the foot of the cliff and this has a protective effect, reducing further wave-erosion. [169] => [170] => Material worn from the margins of the land eventually ends up in the sea. Here it is subject to [[Attrition (erosion)|attrition]] as currents flowing parallel to the coast scour out channels and transport sand and pebbles away from their place of origin. Sediment carried to the sea by rivers settles on the seabed causing [[River delta|deltas]] to form in estuaries. All these materials move back and forth under the influence of waves, tides and currents. Dredging removes material and deepens channels but may have unexpected effects elsewhere on the coastline. Governments make efforts to prevent flooding of the land by the building of [[Breakwater (structure)|breakwaters]], [[seawall]]s, [[Levee|dykes and levees]] and other sea defences. For instance, the [[Thames Barrier]] is designed to protect London from a storm surge,{{cite news |date=5 January 2013 |title=Thames Barrier engineer says second defence needed |newspaper=BBC News |url=https://www.bbc.co.uk/news/uk-england-london-20904885 |url-status=live |access-date=18 September 2013 |archive-url=https://web.archive.org/web/20130926202848/http://www.bbc.co.uk/news/uk-england-london-20904885 |archive-date=26 September 2013}} while the failure of the dykes and levees around [[New Orleans]] during [[Hurricane Katrina]] created a [[humanitarian crisis]] in the United States. [171] => [172] => ==Physical properties== [173] => ===Color=== [174] => [[File:Season-long composites of ocean chlorophyll (8161799575).jpg|thumb|upright=1.6|Ocean [[chlorophyll]] concentration is a proxy for [[phytoplankton]] biomass. In this map, blue colors represent lower chlorophyll and reds represent higher chlorophyll. Satellite-measured chlorophyll is estimated based on [[ocean color]] by how green the color of the water appears from space.]] [175] => [176] => {{excerpt|Ocean color|paragraphs=2-3|file=no}} [177] => [178] => ===Water cycle, weather and rainfall=== [179] => {{Further|Effects of climate change on the water cycle|Water distribution on Earth}} [180] => [[File:Diagram of the Water Cycle.jpg|thumb|upright=1.75|The ocean is a major driver of Earth's [[water cycle]].]] [181] => Ocean water represents the largest body of water within the global [[water cycle]] (oceans contain 97% of [[Water distribution on Earth|Earth's water]]). Evaporation from the ocean moves water into the atmosphere to later rain back down onto land and the ocean.{{cite web|title=The Water Cycle: The Oceans|url=https://www.usgs.gov/special-topic/water-science-school/science/oceans-and-seas-and-water-cycle?qt-science_center_objects=0#qt-science_center_objects|access-date=17 July 2021|publisher=US Geological Survey}} Oceans have a significant effect on the [[biosphere]]. The ocean as a whole is thought to cover approximately 90% of the Earth's [[biosphere]]. Oceanic [[evaporation]], as a phase of the water cycle, is the source of most rainfall (about 90%), causing a global [[cloud cover]] of 67% and a consistent oceanic cloud cover of 72%.{{cite journal | last1=King | first1=Michael D. | last2=Platnick | first2=Steven | last3=Menzel | first3=W. Paul | last4=Ackerman | first4=Steven A. | last5=Hubanks | first5=Paul A. | title=Spatial and Temporal Distribution of Clouds Observed by MODIS Onboard the Terra and Aqua Satellites | journal=IEEE Transactions on Geoscience and Remote Sensing | publisher=Institute of Electrical and Electronics Engineers (IEEE) | volume=51 | issue=7 | year=2013 | issn=0196-2892 | doi=10.1109/tgrs.2012.2227333 | pages=3826–3852| bibcode=2013ITGRS..51.3826K | s2cid=206691291 | doi-access=free| hdl=2060/20120010368 | hdl-access=free }} [[Ocean temperature]]s affect [[climate]] and [[wind]] patterns that affect life on land. One of the most dramatic forms of [[weather]] occurs over the oceans: [[tropical cyclone]]s (also called "typhoons" and "hurricanes" depending upon where the system forms). [182] => [183] => As the world's ocean is the principal component of Earth's [[hydrosphere]], it is integral to [[life]] on Earth, forms part of the [[carbon cycle]] and [[water cycle]], and – as a huge [[Ocean heat content|heat reservoir]] – influences climate and weather patterns. [184] => [185] => ===Waves and swell=== [186] => [[File:Steep deep water wave.ogv|thumb|alt=Diagram showing movement of water as waves pass|Movement of water as waves pass]] [187] => [188] => {{Main|Wind wave|Swell (ocean)}} [189] => [190] => The motions of the ocean surface, known as undulations or [[wind wave]]s, are the partial and alternate rising and falling of the ocean surface. The series of [[mechanical waves]] that propagate along the interface between water and air is called [[Swell (ocean)|swell]] – a term used in [[sailing]], [[surfing]] and [[navigation]].''Observation of swell dissipation across oceans'', F. Ardhuin, Collard, F., and B. Chapron, 2009: Geophys. Res. Lett. 36, L06607, {{doi|10.1029/2008GL037030}} These motions profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from [[Motion sickness|sea sickness]]. [191] => [192] => Wind blowing over the surface of a body of water forms [[Wind wave|waves]] that are perpendicular to the direction of the wind. The friction between air and water caused by a gentle breeze on a pond causes [[Capillary wave|ripples]] to form. A strong blow over the ocean causes larger waves as the moving air pushes against the raised ridges of water. The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in the Southern Hemisphere in the [[Roaring Forties]], long, organized masses of water called [[Swell (ocean)|swell]] roll across the ocean.{{cite book|author=Stow, Dorrik|title=Encyclopedia of the Oceans|publisher=Oxford University Press|year=2004|isbn=978-0-19-860687-1|ref=Stow}}{{rp|pages=83–84}}{{cite web|title=Volumes of the World's Oceans from ETOPO1 |url=http://ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html |publisher=[[National Oceanic and Atmospheric Administration|NOAA]] |access-date=March 7, 2015 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20150311032757/http://ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html |archive-date=March 11, 2015}}{{cite book|last=Young|first=I. R.|url=https://archive.org/details/windgeneratedoce00youn|title=Wind Generated Ocean Waves|publisher=Elsevier|year=1999|isbn=978-0-08-043317-2|page=[https://archive.org/details/windgeneratedoce00youn/page/n101 83]|url-access=limited}} If the wind dies down, the wave formation is reduced, but already-formed waves continue to travel in their original direction until they meet land. The size of the waves depends on the [[Fetch (geography)|fetch]], the distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between the two can produce broken, irregular seas. [193] => [194] => [[Constructive interference]] can lead to the formation of unusually high [[rogue wave]]s.Garrison, Tom (2012). [https://books.google.com/books?id=DVgKAAAAQBAJ&pg=PA204 ''Essentials of Oceanography'']. 6th ed. pp. 204 ff. Brooks/Cole, [[Belmont, California|Belmont]]. {{ISBN|0321814053}}. Most waves are less than {{convert|3|m|sp=us|abbr=on|sigfig=1}} high and it is not unusual for strong storms to double or triple that height.National Meteorological Library and Archive (2010). [http://www.metoffice.gov.uk/media/pdf/b/7/Fact_sheet_No._6.pdf "Fact Sheet 6{{snd}}The Beaufort Scale"]. Met Office ([[Devon, England|Devon]]) Rogue waves, however, have been documented at heights above {{convert|25|m|sp=us}}.{{Cite journal|last1=Holliday|first1=N. P.|last2=Yelland|first2=M. J.|last3=Pascal|first3=R.|last4=Swail|first4=V. R.|last5=Taylor|first5=P. K.|last6=Griffiths|first6=C. R.|last7=Kent|first7=E.|year=2006|title=Were extreme waves in the Rockall Trough the largest ever recorded?|journal=Geophysical Research Letters|volume=33|issue=5|pages=L05613|bibcode=2006GeoRL..33.5613H|doi=10.1029/2005GL025238|doi-access=free}}Laird, Anne (2006). [https://web.archive.org/web/20130408131805/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA462573 "Observed Statistics of Extreme Waves"]. Naval Postgraduate School ([[Monterey, California|Monterey]]). [195] => [196] => The top of a wave is known as the crest, the lowest point between waves is the trough and the distance between the crests is the wavelength. The wave is pushed across the surface of the ocean by the wind, but this represents a transfer of energy and not horizontal movement of water. As waves approach land and [[Waves and shallow water|move into shallow water]], they change their behavior. If approaching at an angle, waves may bend ([[refraction]]) or wrap around rocks and headlands ([[diffraction]]). When the wave reaches a point where its deepest oscillations of the water contact the [[Seabed|ocean floor]], they begin to slow down. This pulls the crests closer together and increases the [[Wave height|waves' height]], which is called [[wave shoaling]]. When the ratio of the wave's height to the water depth increases above a certain limit, it "[[Wave breaking|breaks]]", toppling over in a mass of foaming water. This rushes in a sheet up the beach before retreating into the ocean under the influence of gravity.{{cite web|title=Ocean waves|url=http://oceanexplorer.noaa.gov/edu/learning/player/lesson09.html|access-date=17 April 2013|work=Ocean Explorer|publisher=National Oceanic and Atmospheric Administration}} [197] => [198] => [[Earthquake]]s, [[Types of volcanic eruptions|volcanic eruptions]] or other major geological disturbances can set off waves that can lead to [[tsunamis]] in coastal areas which can be very dangerous.{{cite web|title=Life of a Tsunami|url=http://walrus.wr.usgs.gov/tsunami/basics.html|access-date=14 July 2021|work=Tsunamis & Earthquakes|publisher=US Geological Survey}}{{cite web|title=Physics of Tsunamis|url=https://www.tsunami.gov/?page=tsunamiFAQ|access-date=14 July 2021|publisher=[[National Tsunami Warning Center]] of the USA}} [199] => [200] => ===Sea level and surface=== [201] => {{Further|Sea level|Sea level rise}} [202] => The [[ocean's surface]] is an important reference point for oceanography and geography, particularly as [[mean sea level]]. The ocean surface has globally little, but [[Ocean surface topography|measurable topography]], depending on the ocean's volumes. [203] => [204] => The ocean surface is a crucial interface for oceanic and atmospheric processes. Allowing interchange of particles, enriching the air and water, as well as grounds by some particles becoming [[sediment]]s. This interchange has fertilized life in the ocean, on land and air. All these processes and components together make up [[ocean surface ecosystem]]s. [205] => [206] => ===Tides=== [207] => {{Main|Tide}} [208] => [[File:Bay of Fundy.jpg|thumb|High tide and low tide in the Bay of Fundy, Canada.]] [209] => Tides are the regular rise and fall in water level experienced by oceans, primarily driven by [[the Moon]]'s gravitational [[tidal force]]s upon the Earth. Tidal forces affect all matter on Earth, but only [[fluids]] like the ocean demonstrate the effects on human timescales. (For example, tidal forces acting on rock may produce [[tidal locking]] between two planetary bodies.) Though primarily driven by the Moon's gravity, oceanic tides are also substantially modulated by the Sun's tidal forces, by the rotation of the Earth, and by the shape of the rocky continents blocking oceanic water flow. (Tidal forces vary more with distance than the "base" force of gravity: the Moon's tidal forces on Earth are more than double the Sun's,{{cite web|title=Tides|url=http://oceanexplorer.noaa.gov/edu/learning/player/lesson10.html|access-date=20 April 2013|work=Ocean Explorer|publisher=National Oceanic and Atmospheric Administration}} despite the latter's much stronger gravitational force on Earth. Earth's tidal forces upon the Moon are 20x stronger than the Moon's tidal forces on the Earth.) [210] => [211] => The primary effect of lunar tidal forces is to bulge Earth matter towards the near and far sides of the Earth, relative to the moon. The "perpendicular" sides, from which the Moon appears in line with the local horizon, experience "tidal troughs". Since it takes nearly 25 hours for the Earth to rotate under the Moon (accounting for the Moon's 28 day orbit around Earth), tides thus cycle over a course of 12.5 hours. However, the rocky continents pose obstacles for the tidal bulges, so the timing of tidal maxima may not actually align with the Moon in most localities on Earth, as the oceans are forced to "dodge" the continents. Timing and magnitude of tides vary widely across the Earth as a result of the continents. Thus, knowing the Moon's position does not allow a local to predict tide timings, instead requiring precomputed [[tide table]]s which account for the continents and the Sun, among others. [212] => [213] => During each tidal cycle, at any given place the tidal waters rise to maximum height, high tide, before ebbing away again to the minimum level, low tide. As the water recedes, it gradually reveals the [[foreshore]], also known as the intertidal zone. The difference in height between the high tide and low tide is known as the [[tidal range]] or tidal amplitude.{{cite web |url=http://oceanservice.noaa.gov/education/tutorial_tides/ |title=Tides and Water Levels |work=NOAA Oceans and Coasts |publisher=NOAA Ocean Service Education |access-date=20 April 2013}}{{cite web | url=http://www.arctic.uoguelph.ca/cpe/environments/marine_water/features/Tides/amplitude.htm | title=Tidal amplitudes | publisher=University of Guelph | access-date=12 September 2013}} When the sun and moon are aligned (full moon or new moon), the combined effect results in the higher "spring tides", while the sun and moon misaligning (half moons) result in lesser tidal ranges. [214] => [215] => In the open ocean tidal ranges are less than 1 meter, but in coastal areas these tidal ranges increase to more than 10 meters in some areas.{{Cite book|url=https://www.elsevier.com/books/descriptive-physical-oceanography/talley/978-0-7506-4552-2|title=Descriptive physical oceanography : an introduction|date=2011|publisher=Academic Press|others=Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift|isbn=978-0-7506-4552-2|edition=6th|location=Amsterdam|chapter=Chapter 8. Gravity Waves, Tides, and Coastal Oceanography|oclc=720651296}} Some of the largest tidal ranges in the world occur in the [[Bay of Fundy]] and [[Ungava Bay]] in Canada, reaching up to 16 meters.{{cite web |title=Weird Science: Extreme Tidal Ranges |url=https://manoa.hawaii.edu/exploringourfluidearth/physical/tides/tide-formation-tide-height/weird-science-extreme-tidal-ranges |website=Exploring Our Fluid Earth: Teaching Science as Inquiry |publisher=University of Hawaiʻi |access-date=9 November 2021}} Other locations with record high tidal ranges include the [[Bristol Channel]] between England and Wales, [[Cook Inlet]] in Alaska, and the [[Río Gallegos, Santa Cruz|Río Gallegos]] in Argentina.{{cite web |title=Where are the Highest Tides in the World? |url=https://casualnavigation.com/where-are-the-highest-tides-in-the-world/ |website=Casual Navigation |access-date=9 November 2021}} [216] => [217] => Tides are not to be confused with [[storm surge]]s, which can occur when high winds pile water up against the coast in a shallow area and this, coupled with a low pressure system, can raise the surface of the ocean dramatically above a typical high tide. [218] => [219] => ===Depth=== [220] => {{Further|Bathymetry|}} [221] => [222] => The average depth of the oceans is about 4 km. More precisely the average depth is {{convert|3688|m|ft|sp=us}}. Nearly half of the world's marine waters are over {{convert|3000|m|ft|sp=us}} deep. "Deep ocean," which is anything below 200 meters (660 ft), covers about 66% of Earth's surface.{{cite web|last=Drazen|first=Jeffrey C.|title=Deep-Sea Fishes|url=http://www.soest.hawaii.edu/oceanography/faculty/drazen/fishes.htm|url-status=dead|archive-url=https://archive.today/20120524193114/http://www.soest.hawaii.edu/oceanography/faculty/drazen/fishes.htm|archive-date=May 24, 2012|access-date=June 7, 2007|publisher=School of Ocean and Earth Science and Technology, the [[University of Hawaiʻi at Mānoa]]}} This figure does not include seas not connected to the World Ocean, such as the [[Caspian Sea]]. [223] => [224] => The deepest region of the ocean is at the [[Mariana Trench]], located in the Pacific Ocean near the [[Northern Mariana Islands]].{{Cite news|date=December 7, 2011|title=Scientists map Mariana Trench, deepest known section of ocean in the world|newspaper=The Telegraph|publisher=Telegraph Media Group|url=https://www.telegraph.co.uk/earth/environment/8940571/Scientists-map-Mariana-Trench-deepest-known-section-of-ocean-in-the-world.html|url-status=dead|access-date=March 23, 2012|archive-url=https://web.archive.org/web/20111208045125/http://www.telegraph.co.uk/earth/environment/8940571/Scientists-map-Mariana-Trench-deepest-known-section-of-ocean-in-the-world.html|archive-date=December 8, 2011}} The maximum depth has been estimated to be {{convert|10971|m|ft|sp=us}}. The British naval vessel ''Challenger II'' surveyed the trench in 1951 and named the deepest part of the trench the "[[Challenger Deep]]". In 1960, the [[Bathyscaphe Trieste|Trieste]] successfully reached the bottom of the trench, manned by a crew of two men. [225] => [226] => === Oceanic zones === [227] => {{Further|Ocean stratification}} [228] => [[File:Oceanic divisions.svg|upright=1.8|thumb|The major oceanic zones, based on depth and biophysical conditions |alt=Drawing showing divisions according to depth and distance from shore]] [229] => [230] => [[Oceanography|Oceanographers]] classify the ocean into vertical and horizontal zones based on physical and biological conditions. The [[pelagic zone]] consists of the [[water column]] of the open ocean, and can be divided into further regions categorized by light abundance and by depth. [231] => [232] => ==== Grouped by light penetration ==== [233] => {{Further|Photic zone|Mesopelagic zone|Aphotic zone}} [234] => [235] => The ocean zones can be grouped by light penetration into (from top to bottom): the photic zone, the mesopelagic zone and the aphotic deep ocean zone: [236] => [237] => * The [[photic zone]] is defined to be "the depth at which light intensity is only 1% of the surface value".{{Cite book |last=Bigg |first=Grant R. |url=https://www.cambridge.org/core/books/oceans-and-climate/727BF8A4C403A5AFE5E34791CE830FC3 |title=The Oceans and Climate, Second Edition |date=2003 |publisher=Cambridge University Press |isbn=978-1-139-16501-3 |edition=2 |location=Cambridge |doi=10.1017/cbo9781139165013}}{{rp|36}} This is usually up to a depth of approximately 200 m in the open ocean. It is the region where [[photosynthesis]] can occur and is, therefore, the most [[biodiverse]]. Photosynthesis by plants and microscopic [[algae]] (free floating [[phytoplankton]]) allows the creation of organic matter from chemical precursors including water and carbon dioxide. This organic matter can then be consumed by other creatures. Much of the organic matter created in the photic zone is consumed there but some sinks into deeper waters. The pelagic part of the photic zone is known as the ''epipelagic''. The actual optics of light reflecting and penetrating at the ocean surface are complex.{{rp|34–39}} [238] => * Below the photic zone is the [[Mesopelagic zone|mesopelagic]] or twilight zone where there is a very small amount of light. The basic concept is that with that little light photosynthesis is unlikely to achieve any net growth over respiration.{{rp|116–124}} [239] => * Below that is the aphotic deep ocean to which no surface sunlight at all penetrates. Life that exists deeper than the photic zone must either rely on material sinking from above (see [[marine snow]]) or find another energy source. [[Hydrothermal vents]] are a source of energy in what is known as the [[aphotic zone]] (depths exceeding 200 m). [240] => [241] => ==== Grouped by depth and temperature ==== [242] => The pelagic part of the aphotic zone can be further divided into vertical regions according to depth and temperature: [243] => * The [[mesopelagic]] is the uppermost region. Its lowermost boundary is at a [[thermocline]] of {{convert|12|C|F}} which generally lies at {{convert|700|-|1000|m|ft|sp=us}} in the [[tropics]]. Next is the [[bathypelagic]] lying between {{convert|10|and|4|C|F}}, typically between {{convert|700|-|1000|m|ft|sp=us}} and {{convert|2000|-|4000|m|ft|sp=us}}. Lying along the top of the [[abyssal plain]] is the [[abyssal zone|abyssopelagic]], whose lower boundary lies at about {{convert|6000|m|ft|sp=us}}. The last and deepest zone is the [[hadal zone|hadalpelagic]] which includes the [[oceanic trench]] and lies between {{convert|6000|-|11000|m|ft|sp=us}}. [244] => * The [[benthic]] zones are aphotic and correspond to the three deepest zones of the [[deep-sea]]. The [[bathyal zone]] covers the continental slope down to about {{convert|4000|m|ft|sp=us}}. The abyssal zone covers the abyssal plains between 4,000 and 6,000 m. Lastly, the [[hadal]] zone corresponds to the hadalpelagic zone, which is found in oceanic trenches. [245] => [246] => Distinct boundaries between ocean surface waters and deep waters can be drawn based on the properties of the water. These boundaries are called [[thermocline]]s (temperature), [[halocline]]s (salinity), [[chemocline]]s (chemistry), and [[pycnocline]]s (density). If a zone undergoes dramatic changes in temperature with depth, it contains a [[thermocline]], a distinct boundary between warmer surface water and colder deep water. In tropical regions, the thermocline is typically deeper compared to higher latitudes. Unlike [[Polar regions of Earth|polar waters]], where solar energy input is limited, temperature [[Ocean stratification|stratification]] is less pronounced, and a distinct thermocline is often absent. This is due to the fact that surface waters in polar latitudes are nearly as cold as deeper waters. Below the thermocline, water everywhere in the ocean is very cold, ranging from −1 °C to 3 °C. Because this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9 °C.{{Cite web|title=What is a thermocline?|url=https://oceanservice.noaa.gov/facts/thermocline.html|access-date=February 7, 2021|website=National Ocean Service|publisher=US Department of Commerce|language=en-us}} If a zone undergoes dramatic changes in salinity with depth, it contains a [[halocline]]. If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a [[chemocline]]. Temperature and salinity control ocean water density. Colder and saltier water is denser, and this density plays a crucial role in regulating the global water circulation within the ocean.{{Cite book|url=https://www.elsevier.com/books/descriptive-physical-oceanography/talley/978-0-7506-4552-2|title=Descriptive physical oceanography : an introduction|date=2011|publisher=Academic Press|others=Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift|isbn=978-0-7506-4552-2|edition=6th|location=Amsterdam|chapter=Chapter 3. Physical Properties of Seawater|oclc=720651296}} The halocline often coincides with the thermocline, and the combination produces a pronounced [[pycnocline]], a boundary between less dense surface water and dense deep water. [247] => [248] => ==== Grouped by distance from land ==== [249] => The pelagic zone can be further subdivided into two sub regions based on distance from land: the [[neritic zone]] and the [[oceanic zone]]. The neritic zone covers the water directly above the [[continental shelves]], including [[Coast|coastal waters]]. On the other hand, the oceanic zone includes all the completely open water. [250] => [251] => The [[littoral zone]] covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the [[intertidal]] zone because it is the area where tide level affects the conditions of the region. [252] => [253] => === Volumes === [254] => The combined volume of water in all the oceans is roughly 1.335 billion cubic kilometers (1.335 [[sextillion]] liters, 320.3 million cubic miles).{{cite web|last=Qadri|first=Syed|date=2003|title=Volume of Earth's Oceans|url=http://hypertextbook.com/facts/2001/SyedQadri.shtml|access-date=June 7, 2007|work=The Physics Factbook}}{{cite journal|last1=Charette|first1=Matthew|last2=Smith|first2=Walter H. F.|date=2010|title=The volume of Earth's ocean|journal=Oceanography|volume=23|issue=2|pages=112–114|doi=10.5670/oceanog.2010.51|doi-access=free|hdl=1912/3862|hdl-access=free}}{{excerpt|hydrosphere|paragraphs=2,3|file=no}} [255] => [256] => === Temperature === [257] => {{Main|Ocean temperature|Ocean heat content|Photic zone|l1 = Ocean stratification}} [258] => [259] => Ocean temperatures depends on the amount of solar radiation falling on its surface. In the tropics, with the Sun nearly overhead, the [[Sea surface temperature|temperature of the surface layers]] can rise to over {{convert|30|°C}} while near the [[Polar regions of Earth|poles]] the temperature in equilibrium with the [[sea ice]] is about {{convert|-2|°C}}. There is a continuous circulation of water in the oceans. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface. [[Ocean temperature|Deep ocean water has a temperature]] between {{convert|-2|°C}} and {{convert|5|°C}} in all parts of the globe.{{cite web |url=http://eesc.columbia.edu/courses/ees/climate/lectures/o_circ.html |title=Ocean Circulation |author=Gordon, Arnold |year=2004 |work=The Climate System |publisher=Columbia University |access-date=6 July 2013}} [260] => [261] => The temperature gradient over the water depth is related to the way the surface water mixes with deeper water or does not mix (a lack of mixing is called ''ocean stratification''). This depends on the temperature: in the tropics the warm surface layer of about 100 m is quite stable and does not mix much with deeper water, while near the poles winter cooling and storms makes the surface layer denser and it mixes to great depth and then stratifies again in summer. The [[Photic zone|photic depth]] is typically about 100 m (but varies) and is related to this heated surface layer. [262] => [263] => {{excerpt|Effects of climate change on oceans#Rising ocean temperature|paragraphs=1|file=no}} [264] => [265] => === Temperature and salinity by region === [266] => The temperature and salinity of ocean waters vary significantly across different regions. This is due to differences in the local water balance ([[precipitation]] vs. [[evaporation]]) and the "sea to air" [[temperature gradient]]s. These characteristics can vary widely from one ocean region to another. The table below provides an illustration of the sort of values usually encountered. [267] => {| class="wikitable" style="text-align:center; margin:auto;" [268] => |+General characteristics of ocean surface waters by region{{cite web |title=IPCC Fourth Assessment Report: Climate Change 2007, Working Group I: The Physical Science Basis, 5.6 Synthesis |url=https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-6.html |access-date=19 July 2021 |website=IPCC (archive) |publisher=}}{{cite web |title=Evaporation minus precipitation, Latitude-Longitude, Annual mean |url=http://www.ecmwf.int/research/era/ERA-40/ERA-40_Atlas/docs/section_B/charts/B12_LL_YEA.html |url-status=dead |archive-url=https://web.archive.org/web/20140202152523/http://www.ecmwf.int/research/era/ERA-40/ERA-40_Atlas/docs/section_B/charts/B12_LL_YEA.html |archive-date=February 2, 2014 |work=ERA-40 Atlas |publisher=ECMWF}}{{cite book |last1=Barry |first1=Roger Graham |url=https://archive.org/details/atmosphereweathe00chor |title=Atmosphere, Weather, and Climate |last2=Chorley |first2=Richard J. |date=2003 |publisher=[[Routledge]] |isbn=978-0203440513 |page=[https://archive.org/details/atmosphereweathe00chor/page/n84 68] |url-access=limited}}{{Cite journal |last1=Deser |first1=C. |last2=Alexander |first2=M. A. |last3=Xie |first3=S. P. |author-link3=Shang-Ping Xie |last4=Phillips |first4=A. S. |year=2010 |title=Sea Surface Temperature Variability: Patterns and Mechanisms |url=http://www.cgd.ucar.edu/cas/cdeser/Docs/deser.sstvariability.annrevmarsci10.pdf |url-status=dead |journal=Annual Review of Marine Science |volume=2 |pages=115–143 |bibcode=2010ARMS....2..115D |doi=10.1146/annurev-marine-120408-151453 |pmid=21141660 |archive-url=https://web.archive.org/web/20140514004333/http://www.cgd.ucar.edu/cas/cdeser/Docs/deser.sstvariability.annrevmarsci10.pdf |archive-date=May 14, 2014}}{{Cite book |last=Huang |first=Rui Xin |url=https://www.cambridge.org/au/academic/subjects/earth-and-environmental-science/oceanography-and-marine-science/ocean-circulation-wind-driven-and-thermohaline-processes?format=HB |title=Ocean circulation : wind-driven and thermohaline processes |date=2010 |publisher=Cambridge University Press |isbn=978-0-511-68849-2 |location=Cambridge |oclc=664005236}} [269] => |- [270] => ! scope="col" | Characteristic [271] => ! scope="col" | [[Polar regions of Earth|Polar regions]] [272] => ! scope="col" | [[Temperate climate|Temperate regions]] [273] => ! scope="col" | [[Tropics|Tropical regions]] [274] => |- [275] => | scope="row" | [[Precipitation]] vs. [[evaporation]] [276] => | Precip > Evap [277] => | Precip > Evap [278] => | Evap > Precip [279] => |- [280] => | scope="row" | [[Sea surface temperature]] in winter [281] => | −2 °C [282] => | 5 to 20 °C [283] => | 20 to 25 °C [284] => |- [285] => | scope="row" | Average [[salinity]] [286] => | 28‰ to 32‰ [287] => | 35‰ [288] => | 35‰ to 37‰ [289] => |- [290] => | scope="row" | Annual variation of [[air temperature]] [291] => | ≤ 40 °C [292] => | 10 °C [293] => | < 5 °C [294] => |- [295] => | scope="row" | Annual variation of [[sea temperature|water temperature]] [296] => | < 5 °C [297] => | 10 °C [298] => | < 5 °C [299] => |} [300] => [301] => === Sea ice === [302] => {{Main|Sea ice|Arctic sea ice decline}} [303] => [304] => Seawater with a typical salinity of 35‰ has a freezing point of about −1.8 °C (28.8 °F).{{cite encyclopedia |year=2012 |title=Sea ice |encyclopedia=Encyclopedia Britannica |publisher=Britannica Online Encyclopedia |url=https://www.britannica.com/EBchecked/topic/939404/sea-ice |access-date=21 April 2013 |author=Jeffries, Martin O.}} Because sea ice is less [[Density|dense]] than water, it floats on the ocean's surface (as does [[fresh water]] ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans.{{cite web |last=Wadhams |first=Peter |date=1 January 2003 |title=How Does Arctic Sea Ice Form and Decay? |url=http://www.arctic.noaa.gov/essay_wadhams.html |url-status=dead |archive-url=https://web.archive.org/web/20050306040652/http://www.arctic.noaa.gov/essay_wadhams.html |archive-date=2005-03-06 |access-date=25 April 2005 |work=Arctic theme page |publisher=NOAA}}{{cite book |last=Weeks |first=Willy F. |url=https://books.google.com/books?id=9S55O6WzuL8C&pg=PA2 |title=On Sea Ice |date=2010 |publisher=University of Alaska Press |isbn=978-1-60223-101-6 |page=2}}{{cite book |last1=Shokr |first1=Mohammed |title=Sea Ice – Physics and Remote Sensing |last2=Sinha |first2=Nirmal |date=2015 |publisher=John Wiley & Sons, Inc. |isbn=978-1119027898}} Sea ice usually starts to freeze at the very surface, initially as a very thin ice film. As further freezing takes place, this ice film thickens and can form [[ice sheet]]s. The ice formed incorporates some [[sea salt]], but much less than the seawater it forms from. As the ice forms with low salinity this results in saltier residual seawater. This in turn increases density and promotes vertical sinking of the water.{{Cite web |title=Sea Ice |url=https://nsidc.org/learn/parts-cryosphere/sea-ice |access-date=2022-11-22 |website=National Snow and Ice Data Center |language=en}} [305] => [306] => === Ocean currents and global climate === [307] => {{Further|Ocean current|Thermohaline circulation|Ocean general circulation model}} [308] => [[File:Corrientes-oceanicas.png|thumb|upright=2|Ocean surface currents]] [309] => [[File:Thermohaline Circulation 2.png|A map of the global [[thermohaline circulation]]; blue represents deep-water currents, whereas red represents surface currents.|thumb|upright=1.15|right|alt=World map with colored, directed lines showing how water moves through the oceans. Cold deep water rises and warms in the central Pacific and in the Indian, whereas warm water sinks and cools near Greenland in the North Atlantic and near Antarctica in the South Atlantic.]] [310] => {{See also|Effects of climate change on oceans#Changing ocean currents}} [311] => [312] => ==== Types of ocean currents ==== [313] => An [[ocean current]] is a continuous, directed flow of seawater caused by several forces acting upon the water. These include [[wind]], the [[Coriolis effect]], [[temperature]] and [[salinity]] differences.{{cite web|last1=NOAA|first1=NOAA|title=What is a current?|url=https://oceanservice.noaa.gov/facts/current.html|access-date=13 December 2020|website=Ocean Service Noaa|publisher=National Ocean Service}} Ocean currents are primarily horizontal water movements that have different origins such as tides for tidal currents, or wind and waves for surface currents. [314] => [315] => Tidal currents are in phase with the [[tide]], hence are [[Quasiperiodicity|quasiperiodic]]; associated with the influence of the moon and sun pull on the ocean water. Tidal currents may form various complex patterns in certain places, most notably around [[Cape (geography)|headlands]].{{Cite web|title=Tidal Currents – Currents: NOAA's National Ocean Service Education|url=https://oceanservice.noaa.gov/education/tutorial_currents/02tidal1.html|access-date=February 7, 2021|website=National Ocean Service|publisher=US Department of Commerce|language=en-us}} Non-periodic or non-tidal currents are created by the action of winds and changes in [[density of water]]. In [[littoral zone]]s, [[breaking wave]]s are so intense and the depth measurement so low, that maritime currents reach often 1 to 2 [[Knot (unit)|knots]].{{Cite book|url=https://www.elsevier.com/books/descriptive-physical-oceanography/talley/978-0-7506-4552-2|title=Descriptive physical oceanography : an introduction|date=2011|publisher=Academic Press|others=Lynne D. Talley, George L. Pickard, William J. Emery, James H. Swift|isbn=978-0-7506-4552-2|edition=6th|location=Amsterdam|chapter=Chapter 7. Dynamical Processes for Descriptive Ocean Circulation|oclc=720651296}} [316] => [317] => The [[wind]] and [[wave]]s create surface currents (designated as "drift currents"). These currents can decompose in one quasi-permanent current (which varies within the hourly scale) and one movement of [[Stokes drift]] under the effect of rapid waves movement (which vary on timescales of a couple of seconds). The quasi-permanent current is accelerated by the breaking of waves, and in a lesser governing effect, by the friction of the wind on the surface. [318] => [319] => This acceleration of the current takes place in the direction of waves and dominant wind. Accordingly, when the ocean depth increases, the [[Earth's rotation|rotation]] of the [[earth]] changes the direction of currents in proportion with the increase of depth, while friction lowers their speed. At a certain ocean depth, the current changes direction and is seen inverted in the opposite direction with current speed becoming null: known as the [[Ekman spiral]]. The influence of these currents is mainly experienced at the mixed layer of the ocean surface, often from 400 to 800 meters of maximum depth. These currents can considerably change and are dependent on the yearly [[season]]s. If the mixed layer is less thick (10 to 20 meters), the quasi-permanent current at the surface can adopt quite a different direction in relation to the direction of the wind. In this case, the water column becomes virtually homogeneous above the [[thermocline]]. [320] => [321] => The wind blowing on the ocean surface will set the water in motion. The global pattern of winds (also called [[atmospheric circulation]]) creates a global pattern of ocean currents. These are driven not only by the wind but also by the effect of the circulation of the earth ([[coriolis force]]). These major ocean currents include the [[Gulf Stream]], [[Kuroshio Current|Kuroshio current]], [[Agulhas Current|Agulhas current]] and [[Antarctic Circumpolar Current]]. The Antarctic Circumpolar Current encircles [[Antarctica]] and influences the area's climate, connecting currents in several oceans. [322] => [323] => ==== Relationship of currents and climate ==== [324] => {{Main|Atlantic meridional overturning circulation}} [325] => [[File:FMIB 36754 Gulf-Stream, coupe par l'Itineraire des Paquebots Transatlantiques qui Vont de Havre a New-York.jpeg|thumb|Map of the [[Gulf Stream]], a major ocean current that transports heat from the equator to northern latitudes and moderates the climate of [[Europe]].]] [326] => Collectively, currents move enormous amounts of water and heat around the globe influencing [[climate]]. These wind driven currents are largely confined to the top hundreds of meters of the ocean. At greater depth, the [[thermohaline circulation]] ([[Atlantic meridional overturning circulation]] (AMOC), which is part of a global thermoholine circulation, drives water motion.The AMOC is driven by the cooling of surface waters in the polar latitudes in the north and south, creating dense water which sinks to the bottom of the ocean. This cold and dense water moves slowly away from the [[Geographical pole|poles]] which is why the waters in the deepest layers of the world ocean are so cold. This deep ocean water circulation is relatively slow and water at the bottom of the ocean can be isolated from the ocean surface and atmosphere for hundreds or even a few thousand years. This circulation has important impacts on global climate and the uptake and redistribution of pollutants such as [[carbon dioxide]] by moving these contaminants from the surface into the deep ocean. [327] => [328] => [[Ocean current]]s greatly affect Earth's climate by [[transferring heat]] from the [[tropics]] to the [[polar regions]]. This affects air temperature and precipitation in coastal regions and further inland. Surface heat and freshwater [[flux]]es create global [[density gradient]]s, which drive the [[thermohaline circulation]] that is a part of large-scale ocean circulation. It plays an important role in supplying heat to the polar regions, and thus in [[sea ice]] regulation. [329] => [330] => Oceans moderate the climate of locations where prevailing winds blow in from the ocean. At similar latitudes, a place on Earth with more influence from the ocean will have a more moderate climate than a place with more influence from land. For example, the cities San Francisco (37.8 N) and New York (40.7 N) have different climates because San Francisco has more influence from the ocean. San Francisco, on the west coast of North America, gets [[Westerlies|winds from the west]] over the [[Pacific Ocean]], and the influence of the ocean water yields a more moderate climate with a warmer winter and a longer, cooler summer, with the warmest temperatures happening later in the year. New York, on the east coast of North America gets [[Westerlies|winds from the west]] over land, so New York has colder winters and hotter, earlier summers than San Francisco. [331] => [332] => Warmer ocean currents yield warmer climates in the long term, even at high latitudes. At similar latitudes, a place influenced by warm ocean currents will have a warmer climate overall than a place influenced by cold ocean currents. French Riviera (43.5 N) and Rockland, Maine (44.1 N) have same latitude, but the French Riviera is influenced by warm waters transported by the [[Gulf Stream]] into the [[Mediterranean Sea]] and has a warmer climate overall. Maine is influenced by cold waters transported south by the [[Labrador Current]] giving it a colder climate overall. [333] => [334] => Changes in the thermohaline circulation are thought to have significant impacts on [[Earth's energy budget]]. Because the thermohaline circulation determines the rate at which deep waters reach the surface, it may also significantly influence [[Carbon dioxide in Earth's atmosphere|atmospheric carbon dioxide]] concentrations. Modern observations, [[Climate model|climate simulations]] and paleoclimate reconstructions suggest that the [[Atlantic meridional overturning circulation|Atlantic Meridional Overturning Circulation]] (AMOC) has weakened since the preindustrial era. The latest climate change projections in 2021 suggest that the AMOC is likely to weaken further over the 21st century.IPCC, 2019: [https://www.ipcc.ch/site/assets/uploads/sites/3/2022/03/01_SROCC_SPM_FINAL.pdf Summary for Policymakers]. In: [https://www.ipcc.ch/srocc/ ''IPCC Special Report on the Ocean and Cryosphere in a Changing Climate''] [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. Cambridge University Press, Cambridge and New York. {{doi|10.1017/9781009157964.001}}.{{rp|19}} Such a weakening could cause large changes to global climate, with the North Atlantic particularly vulnerable.{{rp|19}} [335] => [336] => == Chemical properties == [337] => {{main|Seawater#Properties}} [338] => [339] => ===Salinity=== [340] => {{Further|Salinity#Seawater|Seawater#Salinity}} [341] => [[File:WOA09 sea-surf SAL AYool.png|thumb|upright=1.5|Annual mean sea surface salinity in [[practical salinity units]] (psu) from the World Ocean Atlas.{{cite web | last=Baranova | first=Olga | title=World Ocean Atlas 2009 | website=National Centers for Environmental Information (NCEI) | url=https://www.nodc.noaa.gov/OC5/WOA09/pr_woa09.html | access-date=18 January 2022}}]] [342] => [[Salinity]] is a measure of the total amounts of dissolved salts in [[seawater]]. It was originally measured via measurement of the amount of [[chloride]] in seawater and hence termed chlorinity. It is now standard practice to gauge it by measuring [[Electrical resistivity and conductivity|electrical conductivity]] of the water sample. Salinity can be calculated using the chlorinity, which is a measure of the total mass of [[halogen]] ions (includes fluorine, chlorine, bromine, and iodine) in seawater. According to an international agreement, the following formula is used to determine salinity:{{Cite book|last1=Chester|first1=R.|url=https://www.wiley.com/en-us/Marine+Geochemistry%2C+3rd+Edition-p-9781118349090|title=Marine geochemistry|last2=Jickells|first2=Tim|date=2012|publisher=Wiley/Blackwell|isbn=978-1-118-34909-0|edition=3rd|location=Chichester, West Sussex, UK|chapter=Chapter 7: Descriptive oceanography: water-column parameters|oclc=781078031}} [343] => [344] => :Salinity (in ‰) = 1.80655 × Chlorinity (in ‰) [345] => [346] => The average ocean water chlorinity is about 19.2‰, and, thus, the average salinity is around 34.7‰. [347] => [348] => Salinity has a major influence on the density of seawater. A zone of rapid salinity increase with depth is called a [[halocline]]. As [[Salinity#Seawater|seawater]]'s salt content increases, so does the temperature at which its maximum density occurs. Salinity affects both the freezing and boiling points of water, with the boiling point increasing with salinity. At [[atmospheric pressure]],{{cite web|title=Can the ocean freeze? Ocean water freezes at a lower temperature than freshwater.|url=http://oceanservice.noaa.gov/facts/oceanfreeze.html|access-date=January 2, 2019|work=NOAA|archive-date=July 6, 2020|archive-url=https://web.archive.org/web/20200706161806/https://oceanservice.noaa.gov/facts/oceanfreeze.html|url-status=dead}} normal seawater freezes at a temperature of about −2 °C. [349] => [350] => Salinity is higher in Earth's oceans where there is more [[evaporation]] and lower where there is more [[precipitation]]. If precipitation exceeds evaporation, as is the case in [[Polar regions of Earth|polar]] and some [[Temperate climate|temperate regions]], salinity will be lower. Salinity will be higher if evaporation exceeds precipitation, as is sometimes the case in [[Tropics|tropical regions]]. For example, evaporation is greater than precipitation in the [[Mediterranean Sea]], which has an average salinity of 38‰, more saline than the global average of 34.7‰.{{cite web | title=Hydrologic features and climate | website=Encyclopedia Britannica | url=https://www.britannica.com/place/Mediterranean-Sea | access-date=18 January 2022}} Thus, oceanic waters in polar regions have lower salinity content than oceanic waters in tropical regions. However, when [[sea ice]] forms at high latitudes, [[brinicle|salt is excluded]] from the ice as it forms, which can increase the salinity in the residual seawater in polar regions such as the [[Arctic Ocean]].{{cite web | title=Salinity and Brine | website=National Snow and Ice Data Center | url=https://nsidc.org/cryosphere/seaice/characteristics/brine_salinity.html | access-date=18 January 2022}} [351] => [352] => Due to the [[Effects of climate change on oceans#Salinity changes|effects of climate change on oceans]], observations of sea surface salinity between 1950 and 2019 indicate that regions of high salinity and evaporation have become more saline while regions of low salinity and more precipitation have become fresher.Fox-Kemper, B., H.T. Hewitt, C. Xiao, G. Aðalgeirsdóttir, S.S. Drijfhout, T.L. Edwards, N.R. Golledge, M. Hemer, R.E. Kopp, G. Krinner, A. Mix, D. Notz, S. Nowicki, I.S. Nurhati, L. Ruiz, J.-B. Sallée, A.B.A. Slangen, and Y. Yu, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter09.pdf Chapter 9: Ocean, Cryosphere and Sea Level Change]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, New York, USA, pages 1211–1362, {{doi|10.1017/9781009157896.011}} It is very likely that the Pacific and Antarctic/Southern Oceans have freshened while the Atlantic has become more saline. [353] => [354] => === Dissolved gases === [355] => [[File:WOA05 sea-surf O2 AYool.png|thumb|upright=1.2|Sea surface oxygen concentration in moles per cubic meter from the World Ocean Atlas.{{cite book |last1=Garcia |first1=H.E. |last2=Locarnini |first2=R.A. |last3=Boyer |first3=T.P. |last4=Antonov |first4=J.I. |editor1-last=Levitus |editor1-first=S. |title=World Ocean Atlas 2005, Volume 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Oxygen Saturation |date=2006 |publisher=NOAA Atlas NESDIS 63, U.S. Government Printing Office |location=Washington, D.C |pages=342}}]] [356] => Ocean water contains large quantities of dissolved gases, including [[oxygen]], [[carbon dioxide]] and [[nitrogen]]. These dissolve into ocean water via [[gas exchange]] at the ocean surface, with the solubility of these gases depending on the temperature and salinity of the water.{{Cite book|last1=Chester|first1=R.|url=https://www.wiley.com/en-us/Marine+Geochemistry%2C+3rd+Edition-p-9781118349090|title=Marine geochemistry|last2=Jickells|first2=Tim|date=2012|publisher=Wiley/Blackwell|isbn=978-1-118-34909-0|edition=3rd|location=Chichester, West Sussex, UK|chapter=Chapter 8: Air–sea gas exchange|oclc=781078031}} The four most abundant gases in earth's atmosphere and oceans are nitrogen, oxygen, argon, and carbon dioxide. In the ocean by volume, the most abundant gases dissolved in seawater are carbon dioxide (including bicarbonate and carbonate ions, 14 mL/L on average), nitrogen (9 mL/L), and oxygen (5 mL/L) at equilibrium at {{convert|24|C|F|abbr=on}}{{cite book | title=Seawater | chapter=The seawater solution | publisher=Elsevier | year=1995 | doi=10.1016/b978-075063715-2/50007-1 | pages=85–127| isbn=978-0750637152 }}{{cite web|title=Dissolved Gases other than Carbon Dioxide in Seawater|url=http://www.soest.hawaii.edu/oceanography/courses/OCN623/Spring2012/Non_CO2_gases.pdf|access-date=May 5, 2014|publisher=soest.hawaii.edu}}{{cite web|title=Dissolved Oxygen and Carbon Dioxide|url=http://butane.chem.uiuc.edu/pshapley/GenChem1/L23/web-L23.pdf|publisher=chem.uiuc.edu|access-date=February 3, 2014|archive-date=June 12, 2014|archive-url=https://web.archive.org/web/20140612002950/http://butane.chem.uiuc.edu/pshapley/GenChem1/L23/web-L23.pdf|url-status=dead}} All gases are more [[Solubility of gases in liquids|soluble]] – more easily dissolved – in colder water than in warmer water. For example, when salinity and pressure are held constant, oxygen concentration in water almost doubles when the temperature drops from that of a warm summer day {{convert|30|C|F|abbr=on}} to freezing {{convert|0|C|F|abbr=on}}. Similarly, carbon dioxide and nitrogen gases are more [[Solubility of gases in liquids|soluble]] at colder temperatures, and their solubility changes with temperature at different rates.{{cite web|title=12.742. Marine Chemistry. Lecture 8. Dissolved Gases and Air-sea exchange|url=http://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-742-marine-chemistry-fall-2006/lecture-notes/lec_11_gas_exch.pdf|access-date=May 5, 2014}} [357] => [358] => === Oxygen, photosynthesis and carbon cycling === [359] => {{Further|Marine biogeochemical cycles|Ocean deoxygenation|Oceanic carbon cycle|Biological pump}} [360] => [[File:OceanCarbonCycle.jpg|thumb|upright=1.5|Diagram of the ocean carbon cycle showing the relative size of stocks (storage) and fluxes.{{cite web | title=Ocean carbon cycle | website=GRID-Arendal | date=5 June 2009 | url=https://www.grida.no/resources/7555 | access-date=18 January 2022}}]] [361] => [[Photosynthesis]] in the surface ocean releases oxygen and consumes carbon dioxide. [[Phytoplankton]], a type of microscopic free-floating algae, controls this process. After the plants have grown, oxygen is consumed and carbon dioxide released, as a result of bacterial decomposition of the organic matter created by photosynthesis in the ocean. The sinking and bacterial decomposition of some organic matter in deep ocean water, at depths where the waters are out of contact with the atmosphere, leads to a reduction in oxygen concentrations and increase in carbon dioxide, [[carbonate]] and [[bicarbonate]]. This [[Oceanic carbon cycle|cycling of carbon dioxide in oceans]] is an important part of the global [[carbon cycle]]. [362] => [363] => The oceans represent a major [[carbon sink]] for carbon dioxide taken up from the atmosphere by photosynthesis and by dissolution (see also [[carbon sequestration]]). There is also increased attention on carbon dioxide uptake in coastal [[marine habitats]] such as [[mangrove]]s and [[Salt marsh|saltmarshes]]. This process is often referred to as "[[Blue carbon]]". The focus is on these ecosystems because they are strong carbon sinks as well as ecologically important habitats under threat from human activities and [[environmental degradation]]. [364] => [365] => As deep ocean water circulates throughout the globe, it contains gradually less oxygen and gradually more carbon dioxide with more time away from the air at the surface. This gradual decrease in oxygen concentration happens as sinking organic matter continuously gets decomposed during the time the water is out of contact with the atmosphere.{{Cite book |last1=Chester |first1=R. |url=https://www.wiley.com/en-us/Marine+Geochemistry%2C+3rd+Edition-p-9781118349090 |title=Marine geochemistry |last2=Jickells |first2=Tim |date=2012 |publisher=Wiley/Blackwell |isbn=978-1-118-34909-0 |edition=3rd |location=Chichester, West Sussex, UK |chapter=Chapter 9: Nutrients, oxygen, organic carbon and the carbon cycle in seawater |oclc=781078031}} Most of the deep waters of the ocean still contain relatively high concentrations of oxygen sufficient for most animals to survive. However, some ocean areas have very low oxygen due to long periods of isolation of the water from the atmosphere. These oxygen deficient areas, called [[oxygen minimum zone]]s or [[Hypoxia (environmental)|hypoxic]] waters, will generally be made worse by the [[effects of climate change on oceans]].{{Cite journal|last1=Breitburg|first1=Denise|last2=Levin|first2=Lisa A.|last3=Oschlies|first3=Andreas|last4=Grégoire|first4=Marilaure|last5=Chavez|first5=Francisco P.|last6=Conley|first6=Daniel J.|last7=Garçon|first7=Véronique|last8=Gilbert|first8=Denis|last9=Gutiérrez|first9=Dimitri|last10=Isensee|first10=Kirsten|last11=Jacinto|first11=Gil S.|date=2018-01-05|title=Declining oxygen in the global ocean and coastal waters|journal=Science|language=en|volume=359|issue=6371|pages=eaam7240|doi=10.1126/science.aam7240|pmid=29301986|bibcode=2018Sci...359M7240B|issn=0036-8075|doi-access=free}}{{cite journal |last1=Karstensen |first1=J |last2=Stramma |first2=L |last3=Visbeck |first3=M |date=2008 |title=Oxygen minimum zones in the eastern tropical Atlantic and Pacific oceans |url=http://oceanrep.geomar.de/7187/1/95_Karstensen_2008_OxygenMinimumZonesInThe_Artzeit_pubid9275.pdf |journal=Progress in Oceanography |volume=77 |issue=4 |pages=331–350 |bibcode=2008PrOce..77..331K |doi=10.1016/j.pocean.2007.05.009}} [366] => [367] => === pH === [368] => {{Further|pH#Seawater|Seawater#pH|Ocean acidification|}} [369] => [370] => The [[pH value]] at the surface of oceans (''global mean surface pH'') is currently approximately in the range of 8.05{{Cite journal |last1=Terhaar |first1=Jens |last2=Frölicher |first2=Thomas L. |last3=Joos |first3=Fortunat |date=2023 |title=Ocean acidification in emission-driven temperature stabilization scenarios: the role of TCRE and non-{{CO2}} greenhouse gases |journal=Environmental Research Letters |language=en |volume=18 |issue=2 |pages=024033 |bibcode=2023ERL....18b4033T |doi=10.1088/1748-9326/acaf91 |issn=1748-9326 |s2cid=255431338 |quote=Figure 1f|doi-access=free }} to 8.08.Arias, P.A., N. Bellouin, E. Coppola, R.G. Jones, G. Krinner, J. Marotzke, V. Naik, M.D. Palmer, G.-K. Plattner, J. Rogelj, M. Rojas, J. Sillmann, T. Storelvmo, P.W. Thorne, B. Trewin, K. Achuta Rao, B. Adhikary, R.P. Allan, K. Armour, G. Bala, R. Barimalala, S. Berger, J.G. Canadell, C. Cassou, A. Cherchi, W. Collins, W.D. Collins, S.L. Connors, S. Corti, F. Cruz, F.J. Dentener, C. Dereczynski, A. Di Luca, A. Diongue Niang, F.J. Doblas-Reyes, A. Dosio, H. Douville, F. Engelbrecht, V.  Eyring, E. Fischer, P. Forster, B. Fox-Kemper, J.S. Fuglestvedt, J.C. Fyfe, et al., 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf Technical Summary] {{Webarchive|url=https://web.archive.org/web/20220721021347/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf|date=21 July 2022}}. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] {{Webarchive|url=https://web.archive.org/web/20210809131444/https://www.ipcc.ch/report/ar6/wg1/|date=9 August 2021}} [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA (value taken from Figure TS.11 (d) on page 75) This makes it slightly [[Alkalinity|alkaline]]. The pH value at the surface used to be about 8.2 during the past 300 million years.{{cite web |date=27 April 2017 |title=Ocean Acidification |url=https://www.nationalgeographic.com/environment/oceans/critical-issues-ocean-acidification/ |url-status=dead |archive-url=https://web.archive.org/web/20181009211158/https://www.nationalgeographic.com/environment/oceans/critical-issues-ocean-acidification/ |archive-date=9 October 2018 |access-date=9 October 2018 |publisher=[[National Geographic]]}} However, between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05.{{Cite journal |last1=Terhaar |first1=Jens |last2=Frölicher |first2=Thomas L. |last3=Joos |first3=Fortunat |date=2023 |title=Ocean acidification in emission-driven temperature stabilization scenarios: the role of TCRE and non-CO2 greenhouse gases |journal=Environmental Research Letters |language=en |volume=18 |issue=2 |pages=024033 |doi=10.1088/1748-9326/acaf91 |bibcode=2023ERL....18b4033T |s2cid=255431338 |issn=1748-9326|doi-access=free }} [[Carbon dioxide emissions]] from human activities are the primary cause of this process called ''ocean acidification'', with [[Carbon dioxide in Earth's atmosphere|atmospheric carbon dioxide (CO2) levels]] exceeding 410 ppm (in 2020).{{Cite journal |last1=Doney |first1=Scott C. |last2=Busch |first2=D. Shallin |last3=Cooley |first3=Sarah R. |last4=Kroeker |first4=Kristy J. |date=2020-10-17 |title=The Impacts of Ocean Acidification on Marine Ecosystems and Reliant Human Communities |journal=Annual Review of Environment and Resources |volume=45 |issue=1 |pages=83–112 |doi=10.1146/annurev-environ-012320-083019 |s2cid=225741986 |doi-access=free}} [[File:CC-BY icon.svg|50x50px]] Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]] CO2 from the [[atmosphere]] is absorbed by the oceans. This produces [[carbonic acid]] (H2CO3) which dissociates into a [[bicarbonate ion]] ({{Chem2|HCO3-}}) and a [[hydrogen ion]] (H+). The presence of free hydrogen ions (H+) lowers the pH of the ocean. [371] => [372] => There is a natural gradient of pH in the ocean which is related to the breakdown of organic matter in deep water which slowly lowers the pH with depth: The pH value of seawater is naturally as low as 7.8 in deep ocean waters as a result of degradation of organic matter there.{{Cite book |last1=Emerson |first1=Steven |url=https://www.cambridge.org/core/product/identifier/9780511793202/type/book |title=Chemical Oceanography and the Marine Carbon Cycle |last2=Hedges |first2=John |year=2008 |publisher=Cambridge University Press |isbn=978-0-521-83313-4 |edition=1 |chapter=Chapter 4: Carbonate chemistry |doi=10.1017/cbo9780511793202}} It can be as high as 8.4 in surface waters in areas of high [[biological productivity]]. [373] => [374] => The definition of ''global mean surface pH'' refers to the top layer of the water in the ocean, up to around 20 or 100 m depth. In comparison, the average depth of the ocean is about 4 km. The pH value at greater depths (more than 100 m) has not yet been affected by ocean acidification in the same way. There is a large body of deeper water where the natural gradient of pH from 8.2 to about 7.8 still exists and it will take a very long time to acidify these waters, and equally as long to recover from that acidification. But as the top layer of the ocean (the [[photic zone]]) is crucial for its marine productivity, any changes to the pH value and temperature of the top layer can have many knock-on effects, for example on [[marine life]] and [[ocean current]]s (see also [[effects of climate change on oceans]]). [375] => [376] => The key issue in terms of the penetration of ocean acidification is the way the surface water mixes with deeper water or does not mix (a lack of mixing is called [[ocean stratification]]). This in turn depends on the water temperature and hence is different between the tropics and the polar regions (see [[ocean#Temperature]]). [377] => [378] => The [[Chemical property|chemical properties]] of seawater complicate pH measurement, and several distinct pH scales exist in [[chemical oceanography]].Zeebe, R. E. and Wolf-Gladrow, D. (2001) ''CO2 in seawater: equilibrium, kinetics, isotopes'', Elsevier Science B.V., Amsterdam, Netherlands {{ISBN|0-444-50946-1}} There is no universally accepted reference pH-scale for seawater and the difference between measurements based on multiple reference scales may be up to 0.14 units.Stumm, W, Morgan, J. J. (1981) ''Aquatic Chemistry, An Introduction Emphasizing Chemical Equilibria in Natural Waters''. John Wiley & Sons. pp. 414–416. {{ISBN|0471048313}}. [379] => [380] => === Alkalinity === [381] => {{Further|Alkalinity#Changes to oceanic alkalinity|4=}} [382] => [383] => [[Alkalinity]] is the balance of base (proton acceptors) and acids (proton donors) in seawater, or indeed any natural waters. The alkalinity acts as a [[chemical buffer]], regulating the pH of seawater. While there are many ions in seawater that can contribute to the alkalinity, many of these are at very low concentrations. This means that the carbonate, bicarbonate and borate ions are the only significant contributors to seawater alkalinity in the open ocean with well oxygenated waters. The first two of these ions contribute more than 95% of this alkalinity. [384] => [385] => The chemical equation for alkalinity in seawater is: [386] => : AT = [HCO3-] + 2[CO32-] + [B(OH)4-] [387] => [388] => The growth of phytoplankton in surface ocean waters leads to the conversion of some bicarbonate and carbonate ions into organic matter. Some of this organic matter sinks into the deep ocean where it is broken down back into carbonate and bicarbonate. This process is related to ocean productivity or [[marine primary production]]. Thus alkalinity tends to increase with depth and also along the global thermohaline circulation from the Atlantic to the Pacific and Indian Ocean, although these increases are small. The concentrations vary overall by only a few percent. [389] => [390] => The absorption of CO2 from the atmosphere does not affect the ocean's [[alkalinity]].IPCC, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf Annex VII: Glossary] {{Webarchive|url=https://web.archive.org/web/20220605175306/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf|date=5 June 2022}} [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] {{Webarchive|url=https://web.archive.org/web/20210809131444/https://www.ipcc.ch/report/ar6/wg1/|date=9 August 2021}} [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA{{rp|2252}} It does lead to a reduction in pH value though (termed [[ocean acidification]]). [391] => [392] => === Residence times of chemical elements and ions === [393] => [[File:Sydney (AU), Coast, New Zealand sea lions -- 2019 -- 3489.jpg|thumb|Residence time of elements in the ocean depends on supply by processes like [[weathering|rock weathering]] and [[river]]s vs. removal by processes like [[evaporation]] and [[sedimentation]].]] [394] => The ocean waters contain many [[chemical element]]s as dissolved ions. Elements dissolved in ocean waters have a wide range of concentrations. Some elements have very high concentrations of several grams per liter, such as [[sodium]] and [[chloride]], together making up the majority of ocean salts. Other elements, such as [[iron]], are present at tiny concentrations of just a few nanograms (10−9 grams) per liter. [395] => [396] => The concentration of any element depends on its rate of supply to the ocean and its rate of removal. Elements enter the ocean from rivers, the atmosphere and [[hydrothermal vent]]s. Elements are removed from ocean water by sinking and becoming buried in [[sediment]]s or evaporating to the [[atmosphere]] in the case of water and some gases. By estimating the [[residence time]] of an element, oceanographers examine the balance of input and removal. Residence time is the average time the element would spend dissolved in the ocean before it is removed. Heavily abundant elements in ocean water such as sodium, have high input rates. This reflects high abundance in rocks and rapid rock weathering, paired with very slow removal from the ocean due to sodium ions being comparatively unreactive and highly soluble. In contrast, other elements such as iron and [[aluminium]] are abundant in rocks but very insoluble, meaning that inputs to the ocean are low and removal is rapid. These cycles represent part of the major global cycle of elements that has gone on since the Earth first formed. The residence times of the very abundant elements in the ocean are estimated to be millions of years, while for highly reactive and insoluble elements, residence times are only hundreds of years. [397] => {| class="wikitable" style="text-align:right; margin:auto;" [398] => |+Residence times of elements and ions{{cite web|title=Calculation of residence times in seawater of some important solutes|url=http://www.gly.uga.edu/railsback/3030/3030Tres.pdf|publisher=gly.uga.edu|access-date=February 3, 2014|archive-date=November 23, 2018|archive-url=https://web.archive.org/web/20181123192418/http://www.gly.uga.edu/railsback/3030/3030Tres.pdf|url-status=dead}}{{Cite book|last1=Chester|first1=R.|url=https://www.wiley.com/en-us/Marine+Geochemistry%2C+3rd+Edition-p-9781118349090|title=Marine geochemistry|last2=Jickells|first2=Tim|date=2012|publisher=Wiley/Blackwell|isbn=978-1-118-34909-0|edition=3rd|location=Chichester, West Sussex, UK|chapter=Chapter 11: Trace elements in the oceans|oclc=781078031}} [399] => |- [400] => ! scope="col" | Chemical element or ion [401] => ! scope="col" | Residence time (years) [402] => |- [403] => ! scope="row" | [[Chloride]] (Cl−) [404] => | 100,000,000 [405] => |- [406] => ! scope="row" | [[Sodium]] (Na+) [407] => | 68,000,000 [408] => |- [409] => ! scope="row" | [[Magnesium]] (Mg2+) [410] => | 13,000,000 [411] => |- [412] => ! scope="row" | [[Potassium]] (K+) [413] => | 12,000,000 [414] => |- [415] => ! scope="row" | [[Sulfate]] (SO42−) [416] => | 11,000,000 [417] => |- [418] => ! scope="row" | [[Calcium]] (Ca2+) [419] => | 1,000,000 [420] => |- [421] => ! scope="row" | [[Carbonate]] (CO32−) [422] => | 110,000 [423] => |- [424] => ! scope="row" | [[Silicon]] (Si) [425] => | 20,000 [426] => |- [427] => ! scope="row" | [[Water]] (H2O) [428] => | 4,100 [429] => |- [430] => ! scope="row" | [[Manganese]] (Mn) [431] => | 1,300 [432] => |- [433] => ! scope="row" | [[Aluminium|Aluminum]] (Al) [434] => | 600 [435] => |- [436] => ! scope="row" | [[Iron]] (Fe) [437] => | 200 [438] => |} [439] => [440] => === Nutrients === [441] => {{See also|Eutrophication#Coastal waters}} [442] => {{oceanic gyres|[[Ocean gyre]]s rotate clockwise in the north and counterclockwise in the south}} [443] => A few elements such as [[nitrogen]], [[phosphorus]], [[iron]], and [[potassium]] essential for life, are major components of biological material, and are commonly known as "[[nutrient]]s". Nitrate and phosphate have ocean [[residence time]]s of 10,000{{Cite web|title=Monterey Bay Aquarium Research Institute|url=https://www.mbari.org/wp-content/static/chemsensor/n/nitrogen.html}} and 69,000{{Cite web|title=Monterey Bay Aquarium Research Institute|url=https://www.mbari.org/wp-content/static/chemsensor/p/phosphorus.html}} years, respectively, while potassium is a much more abundant ion in the ocean with a residence time of 12 million{{Cite web|url=https://www3.mbari.org/chemsensor/k/potassium.html|title=Potassium|website=www3.mbari.org}} years. The biological cycling of these elements means that this represents a continuous removal process from the ocean's water column as degrading organic material sinks to the ocean floor as [[sediment]]. [444] => [445] => Phosphate from [[Intensive farming|intensive agriculture]] and [[Sewage treatment|untreated sewage]] is transported via runoff to rivers and coastal zones to the ocean where it is metabolized. Eventually, it sinks to the ocean floor and is no longer available to humans as a commercial resource.{{Cite journal|last1=Paytan|first1=Adina|last2=McLaughlin|first2=Karen|date=2007|title=The Oceanic Phosphorus Cycle|url=https://pubs.acs.org/doi/10.1021/cr0503613|journal=Chemical Reviews|language=en|volume=107|issue=2|pages=563–576|doi=10.1021/cr0503613|pmid=17256993|s2cid=1872341 |issn=0009-2665}} Production of [[Phosphorite|rock phosphate]], an essential ingredient in inorganic [[fertilizer]],{{Cite journal |last1=Cordell |first1=Dana |author-link=Dana Cordell |last2=Drangert |first2=Jan-Olof |last3=White |first3=Stuart |date=2009 |title=The story of phosphorus: Global food security and food for thought |url=https://linkinghub.elsevier.com/retrieve/pii/S095937800800099X |journal=Global Environmental Change |language=en |volume=19 |issue=2 |pages=292–305 |doi=10.1016/j.gloenvcha.2008.10.009|s2cid=1450932 }} is a slow geological process that occurs in some of the world's ocean sediments, rendering mineable sedimentary [[apatite]] (phosphate) a [[non-renewable resource]] (see [[peak phosphorus]]). This continual net deposition loss of non-renewable phosphate from human activities, may become a resource issue for fertilizer production and [[food security]] in future.{{Cite journal|last1=Edixhoven|first1=J. D.|last2=Gupta|first2=J.|author2-link=Joyeeta Gupta|last3=Savenije|first3=H. H. G.|date=2014-12-19|title=Recent revisions of phosphate rock reserves and resources: a critique|url=https://esd.copernicus.org/articles/5/491/2014/|journal=Earth System Dynamics|language=en|volume=5|issue=2|pages=491–507|doi=10.5194/esd-5-491-2014|bibcode=2014ESD.....5..491E|s2cid=858311 |issn=2190-4987|doi-access=free}}{{cite journal|last1=Amundson|first1=R.|last2=Berhe|first2=A. A.|last3=Hopmans|first3=J. W.|last4=Olson|first4=C.|last5=Sztein|first5=A. E.|last6=Sparks|first6=D. L.|year=2015|title=Soil and human security in the 21st century|url=http://www.escholarship.org/uc/item/8f42m6w4|journal=Science|volume=348|issue=6235|pages=1261071|doi=10.1126/science.1261071|issn=0036-8075|pmid=25954014|s2cid=206562728}} [446] => [447] => == Marine life == [448] => {{Main|Marine life|Marine habitats|Marine primary production|Marine biology|Marine ecosystem}} [449] => [450] => [[File:Representative ocean animal life.jpg|thumb|upright=2|left| Some representative ocean animals (not drawn to scale) within their approximate depth-defined ecological habitats. [[Marine microorganisms]] also exist on the surfaces and within the tissues and organs of the diverse life inhabiting the ocean, across all ocean habitats. The animals rooted to or living on the ocean floor are not [[pelagic]] but are [[benthic]] animals.Apprill, A. (2017)"Marine animal microbiomes: toward understanding host–microbiome interactions in a changing ocean". ''Frontiers in Marine Science'', '''4''': 222. {{doi|10.3389/fmars.2017.00222}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].]] [451] => [452] => Life within the ocean [[evolution|evolved]] 3 billion years prior to life on land. Both the depth and the distance from shore strongly influence the [[biodiversity]] of the plants and animals present in each region.{{cite book|title=Biology: Concepts & Connections|at=section 34.7|chapter=Chapter 34: The Biosphere: An Introduction to Earth's Diverse Environment|chapter-url=http://wps.aw.com/bc_campbell_concepts_7_oa/215/55135/14114612.cw/-/t/index.html|access-date=May 14, 2014|archive-date=July 13, 2018|archive-url=https://web.archive.org/web/20180713043836/http://wps.aw.com/bc_campbell_concepts_7_oa/215/55135/14114612.cw/-/t/index.html|url-status=dead}} The diversity of life in the ocean is immense, including: [453] => * [[Animals]]: most animal [[phylum|phyla]] have species that inhabit the ocean, including many that are found only in marine environments such as [[Porifera|sponges]], [[Cnidaria]] (such as [[coral]]s and [[jellyfish]]), [[Ctenophora|comb jellies]], [[Brachiopod]]s, and [[Echinoderm]]s (such as [[sea urchin]]s and [[sea star]]s). Many other familiar animal groups primarily live in the ocean, including [[cephalopod]]s (includes [[octopus]] and [[squid]]), [[crustacean]]s (includes [[lobster]]s, [[crab]]s, and [[shrimp]]), [[fish]], [[sharks]], [[cetacean]]s (includes [[whale]]s, [[dolphin]]s, and [[porpoise]]s). In addition, many land animals have adapted to living a major part of their life on the oceans. For instance, [[seabirds]] are a diverse group of birds that have adapted to a life mainly on the oceans. They feed on marine animals and spend most of their lifetime on water, many going on land only for breeding. Other birds that have adapted to oceans as their living space are [[penguin]]s, [[Gull|seagulls]] and [[Pelecaniformes|pelicans]]. Seven species of turtles, the [[sea turtle]]s, also spend most of their time in the oceans. [454] => * [[Plants]]: including [[seagrass|sea grasses]], or [[mangroves]] [455] => * [[Algae]]: algae is a "catch-all" term to include many [[photosynthesis|photosynthetic]], [[protist|single-celled]] [[eukaryote]]s, such as [[green algae]], [[diatom]]s, and [[dinoflagellates]], but also multicellular algae, such as some [[red algae]] (including organisms like [[Pyropia]], which is the source of the edible [[nori]] seaweed), and [[brown algae]] (including organisms like [[kelp]]). [456] => * [[Bacteria]]: ubiquitous single-celled [[prokaryotes]] found throughout the world [457] => * [[Archaea]]: [[prokaryotes]] distinct from bacteria, that inhabit many environments of the ocean, as well as many [[extremophile|extreme environments]] [458] => * [[Fungi]]: many [[marine fungi]] with diverse roles are found in oceanic environments [459] => {{excerpt|marine life|paragraphs=1}} [460] => [461] => {{excerpt|marine habitat|paragraphs=1|file=no}} [462] => [463] => {{excerpt|marine ecosystem|paragraphs=1}} [464] => [465] => ==Human uses of the oceans== [466] => {{Main|Sea#Humans and the sea|The sea in culture}} [467] => [[File:Exclusive Economic Zones by boundary type.png|thumb|upright=1.5|Global map of all [[Exclusive Economic Zone]]s]] [468] => The ocean has been linked to human activity throughout history. These activities serve a wide variety of purposes, including [[History of navigation|navigation and exploration]], [[naval warfare]], travel, [[Freight transport|shipping]] and [[trade]], food production (e.g. [[fishing]], [[whaling]], [[seaweed farming]], [[aquaculture]]), leisure ([[Cruising (maritime)|cruising]], [[sailing]], [[recreational boat fishing]], [[scuba diving]]), power generation (see [[marine energy]] and [[offshore wind power]]), extractive industries ([[offshore drilling]] and [[deep sea mining]]), [[Fresh water|freshwater]] production via [[desalination]]. [469] => [470] => Many of the world's goods are moved by [[ship]] between the world's [[seaport]]s.{{Cite book|last=Zacharias|first=Mark|url=https://books.google.com/books?id=Ir0TAwAAQBAJ&q=Many+of+the+world's+goods+are+moved+by+ship+between+seaports.&pg=PA220|title=Marine Policy: An Introduction to Governance and International Law of the Oceans|year= 2014|publisher=Routledge|isbn=978-1136212475|language=en}} Large quantities of goods are transported across the ocean, especially across the Atlantic and around the Pacific Rim.{{Cite journal|last1=Halpern|first1=Benjamin S.|last2=Walbridge|first2=Shaun|last3=Selkoe|first3=Kimberly A.|last4=Kappel|first4=Carrie V.|last5=Micheli|first5=Fiorenza|last6=D'Agrosa|first6=Caterina|last7=Bruno|first7=John F.|last8=Casey|first8=Kenneth S.|last9=Ebert|first9=Colin|last10=Fox|first10=Helen E.|last11=Fujita|first11=Rod|date=2008|title=A Global Map of Human Impact on Marine Ecosystems|url=https://www.science.org/doi/10.1126/science.1149345|journal=Science|language=en|volume=319|issue=5865|pages=948–952|doi=10.1126/science.1149345|pmid=18276889 |bibcode=2008Sci...319..948H |s2cid=26206024 |issn=0036-8075}} Many types of cargo including manufactured goods, are typically transported in [[Shipping container|standard sized, lockable containers]] that are loaded on purpose-built [[container ship]]s at [[Container port|dedicated terminals]].{{cite book|author=Sauerbier, Charles L.|title=Marine Cargo Operations: a guide to stowage|author2=Meurn, Robert J.|publisher=Cornell Maritime Press|year=2004|isbn=978-0-87033-550-1|location=Cambridge, Md|pages=1–16}} Containerization greatly boosted the efficiency and reduced the cost of shipping products by sea. This was a major factor in the rise of [[globalization]] and exponential increases in [[international trade]] in the mid-to-late 20th century.{{Cite web|title=Industry Globalization {{!}} World Shipping Council|url=https://www.worldshipping.org/about-the-industry/history-of-containerization/industry-globalization|access-date=2021-05-04|website=www.worldshipping.org|archive-date=January 27, 2021|archive-url=https://web.archive.org/web/20210127201742/https://www.worldshipping.org/about-the-industry/history-of-containerization/industry-globalization|url-status=dead}} [471] => [472] => Oceans are also the major supply source for the [[fishing industry]]. Some of the major harvests are [[shrimp]], [[fish]], [[crabs]], and [[lobster]]. The biggest global commercial fishery is for [[Anchovy|anchovies]], [[Alaska pollock]] and [[tuna]].{{Cite book|url=http://www.fao.org/documents/card/en/c/ca9229en|title=The State of World Fisheries and Aquaculture 2020|date=2020|publisher=FAO|isbn=978-92-5-132692-3|language=en|doi=10.4060/ca9229en|hdl=10535/3776|s2cid=242949831 }}{{rp|6}} A report by [[Food and Agriculture Organization|FAO]] in 2020 stated that "in 2017, 34 percent of the fish stocks of the world's marine fisheries were classified as [[Overfishing|overfished]]".{{rp|54}} Fish and other fishery products from both [[wild fisheries]] and aquaculture are among the most widely consumed sources of protein and other essential nutrients. Data in 2017 showed that "fish consumption accounted for 17 percent of the global population's intake of animal proteins". To fulfill this need, coastal countries have exploited marine resources in their [[exclusive economic zone]]. Fishing vessels are increasingly venturing out to exploit stocks in international waters.{{cite web|title=Fisheries: Latest data|url=http://www.greenfacts.org/en/fisheries/|access-date=23 April 2013|publisher=GreenFacts}} [473] => [474] => The ocean has a vast amount of [[energy]] carried by [[ocean wave]]s, [[tide]]s, [[salinity]] differences, and [[Ocean thermal energy|ocean temperature differences]] which can be harnessed to [[Electricity generation|generate electricity]].{{cite web|year=2014|title=What is Ocean Energy|url=https://www.ocean-energy-systems.org/ocean-energy/what-is-ocean-energy/|access-date=14 May 2021|publisher=Ocean Energy Systems}} Forms of [[Sustainable energy|sustainable marine energy]] include [[tidal power]], [[Ocean thermal energy conversion|ocean thermal energy]] and [[wave power]].{{Cite book|last1=Cruz|first1=João|url=https://archive.org/details/oceanwaveenergyc00cruz|title=Ocean Wave Energy – Current Status and Future Perspectives|publisher=Springer|year=2008|isbn=978-3-540-74894-6|page=[https://archive.org/details/oceanwaveenergyc00cruz/page/n15 2]|url-access=limited}} [[Offshore wind power]] is captured by [[wind turbine]]s placed out on the ocean; it has the advantage that wind speeds are higher than on land, though wind farms are more costly to construct offshore.{{cite web|date=22 November 2010|title=Offshore Wind Power 2010|url=http://btm.dk/news/offshore+wind+power+2010/?s=9&p=&n=39|url-status=dead|archive-url=https://web.archive.org/web/20110630030725/http://btm.dk/news/offshore+wind+power+2010/?s=9&p=&n=39|archive-date=30 June 2011|access-date=25 April 2013|publisher=BTM Consult|df=dmy-all}} There are large deposits of [[petroleum]], as oil and [[natural gas]], in rocks beneath the ocean floor. [[Oil platform|Offshore platforms]] and [[drilling rig]]s [[Offshore drilling|extract]] the oil or gas and store it for transport to land.{{cite web|author=Lamb, Robert|year=2011|title=How offshore drilling works|url=http://science.howstuffworks.com/environmental/energy/offshore-drilling.htm|access-date=6 May 2013|work=HowStuffWorks}} [475] => [476] => "Freedom of the seas" is a principle in [[international law]] dating from the seventeenth century. It stresses freedom to navigate the oceans and disapproves of war fought in [[international waters]].{{cite web|title=The United Nations Convention on the Law of the Sea (A historical perspective)|url=http://www.un.org/Depts/los/convention_agreements/convention_historical_perspective.htm|access-date=8 May 2013|publisher=United Nations Division for Ocean Affairs and the Law of the Sea}} Today, this concept is enshrined in the [[United Nations Convention on the Law of the Sea]] (UNCLOS). [477] => [478] => The [[International Maritime Organization]] (IMO), which was ratified in 1958, is mainly responsible for [[maritime safety]], liability and compensation, and has held some conventions on marine pollution related to shipping incidents. [[Ocean governance]] is the conduct of the policy, actions and affairs regarding the world's [[oceans]].{{Cite book|last=Evans|first=J. P.|url=https://www.routledge.com/Environmental-Governance/Evans/p/book/9780415589826|title=Environmental Governance.|date=2011|publisher=Taylor & Francis|isbn=978-0-203-15567-7|location=Hoboken|oclc=798531922}} [479] => [480] => ==Threats from human activities== [481] => [[File:Global cumulative human impact on the ocean.png|thumb|upright=1.5| {{center|Global cumulative human impact on the ocean{{cite journal | last1 = Halpern | first1 = B.S. | last2 = Frazier | first2 = M. | last3 = Afflerbach | first3 = J. | display-authors = etal | year = 2019 | title = Recent pace of change in human impact on the world's ocean | journal = Scientific Reports | volume = 9 | issue = 1| page = 11609 | doi = 10.1038/s41598-019-47201-9 | pmid = 31406130 | pmc = 6691109 | bibcode = 2019NatSR...911609H}}}}]] [482] => {{Further|Human impact on marine life}}Human activities affect [[marine life]] and [[marine habitat]]s through many negative influences, such as [[marine pollution]] (including [[marine debris]] and [[microplastics]]) [[overfishing]], [[ocean acidification]] and other [[effects of climate change on oceans]]. [483] => [484] => === Climate change === [485] => {{excerpt|Effects of climate change on oceans|file=no}} [486] => [487] => === Marine pollution === [488] => {{excerpt|Marine pollution|file=no|paragraphs=1-2}} [489] => [490] => ====Plastic pollution==== [491] => {{excerpt|Plastic soup|file=no|paragraphs=1-2}} [492] => [493] => ===Overfishing=== [494] => {{excerpt|Overfishing|file=no|paragraphs=1}} [495] => [496] => ==Protection== [497] => {{Main|Marine conservation|marine protected area}} [498] => Ocean protection serves to safeguard the ecosystems in the oceans upon which humans depend.{{cite web |date=26 March 2014 |title=Protecting the Marine Environment |url=https://www.epa.gov/international-cooperation/protecting-marine-environment |access-date=25 October 2021 |website=www.epa.gov |language=en}}{{cite web |title=Quantitative targets for marine protection: a review of the scientific basis and applications |url=https://www.doc.govt.nz/globalassets/documents/conservation/marine-and-coastal/marine-protected-areas/mpa-publications/mpa-targets-review-2020.pdf |access-date=25 October 2021}} Protecting these ecosystems from threats is a major component of [[environmental protection]]. One of protective measures is the creation and enforcement of [[marine protected area]]s (MPAs). Marine protection may need to be considered within a national, regional and international context.{{cite web |last1=Farran |first1=Sue |title=Is marine protection compatible with the right to economic development in Pacific Island States? |url=https://core.ac.uk/reader/196575674}} Other measures include supply chain transparency requirement policies, policies to prevent marine pollution, ecosystem-assistance (e.g. [[Coral bleaching#Artificial assistance|for coral reefs]]) and support for [[sustainable seafood]] (e.g. [[Sustainable fishery#Remediation|sustainable fishing practices and types of aquaculture]]). There is also the protection of marine resources and components whose extraction or disturbance would cause substantial harm, engagement of broader publics and impacted communities,{{cite journal |last1=Manson |first1=Paul |last2=Nielsen-Pincus |first2=Max |last3=Granek |first3=Elise F. |last4=Swearingen |first4=Thomas C. |title=Public perceptions of ocean health and marine protection: Drivers of support for Oregon's marine reserves |journal=Ocean & Coastal Management |date=15 February 2021 |volume=201 |pages=105480 |doi=10.1016/j.ocecoaman.2020.105480 |bibcode=2021OCM...20105480M |s2cid=230555294 |language=en |issn=0964-5691|doi-access=free }} and the development of ocean clean-up projects ([[Marine plastic pollution#Reduction efforts|removal of marine plastic pollution]]). Examples of the latter include [[Clean Oceans International]] and [[The Ocean Cleanup]]. [499] => [500] => In 2021, 43 expert scientists published the first scientific framework version that – via integration, [[scientific review|review]], clarifications and [[standardization]] – enables the evaluation of levels of protection of [[marine protected area]]s and can serve as a guide for any subsequent efforts to improve, plan and monitor marine protection quality and extents. Examples are the efforts towards the 30%-protection-goal of the "Global Deal For Nature"{{cite journal |last1=Dinerstein |first1=E. |last2=Vynne |first2=C. |last3=Sala |first3=E. |last4=Joshi |first4=A. R. |last5=Fernando |first5=S. |last6=Lovejoy |first6=T. E. |last7=Mayorga |first7=J. |last8=Olson |first8=D. |last9=Asner |first9=G. P. |last10=Baillie |first10=J. E. M. |last11=Burgess |first11=N. D. |last12=Burkart |first12=K. |last13=Noss |first13=R. F. |last14=Zhang |first14=Y. P. |last15=Baccini |first15=A. |last16=Birch |first16=T. |last17=Hahn |first17=N. |last18=Joppa |first18=L. N. |last19=Wikramanayake |first19=E. |title=A Global Deal For Nature: Guiding principles, milestones, and targets |journal=Science Advances |year=2019 |volume=5 |issue=4 |pages=eaaw2869 |doi=10.1126/sciadv.aaw2869|pmid=31016243 | pmc=6474764|bibcode=2019SciA....5.2869D }} and the UN's [[Sustainable Development Goal 14]] ("life below water").{{cite news |title=Improving ocean protection with the first marine protected areas guide |url=https://phys.org/news/2021-09-ocean-marine-areas.html |access-date=19 October 2021 |work=Institut de Recherche pour le Développement |language=en}}{{cite journal |last1=Grorud-Colvert |first1=Kirsten |last2=Sullivan-Stack |first2=Jenna |last3=Roberts |first3=Callum |last4=Constant |first4=Vanessa |last5=Horta e Costa |first5=Barbara |last6=Pike |first6=Elizabeth P. |last7=Kingston |first7=Naomi |last8=Laffoley |first8=Dan |last9=Sala |first9=Enric |last10=Claudet |first10=Joachim |last11=Friedlander |first11=Alan M. |last12=Gill |first12=David A. |last13=Lester |first13=Sarah E. |last14=Day |first14=Jon C. |last15=Gonçalves |first15=Emanuel J. |last16=Ahmadia |first16=Gabby N. |last17=Rand |first17=Matt |last18=Villagomez |first18=Angelo |last19=Ban |first19=Natalie C. |last20=Gurney |first20=Georgina G. |last21=Spalding |first21=Ana K. |last22=Bennett |first22=Nathan J. |last23=Briggs |first23=Johnny |last24=Morgan |first24=Lance E. |last25=Moffitt |first25=Russell |last26=Deguignet |first26=Marine |last27=Pikitch |first27=Ellen K. |last28=Darling |first28=Emily S. |last29=Jessen |first29=Sabine |last30=Hameed |first30=Sarah O. |last31=Di Carlo |first31=Giuseppe |last32=Guidetti |first32=Paolo |last33=Harris |first33=Jean M. |last34=Torre |first34=Jorge |last35=Kizilkaya |first35=Zafer |last36=Agardy |first36=Tundi |last37=Cury |first37=Philippe |last38=Shah |first38=Nirmal J. |last39=Sack |first39=Karen |last40=Cao |first40=Ling |last41=Fernandez |first41=Miriam |last42=Lubchenco |first42=Jane |title=The MPA Guide: A framework to achieve global goals for the ocean |journal=Science |year=2021 |volume=373 |issue=6560 |pages=eabf0861 |doi=10.1126/science.abf0861|pmid=34516798 |s2cid=237473020 |url=https://archimer.ifremer.fr/doc/00723/83464/88455.pdf }} [501] => [502] => In March 2023 a [[High Seas Treaty]] was signed. It is legally binding. The main achievement is the new possibility to create marine protected areas in international waters. By doing so the agreement now makes it possible to protect 30% of the oceans by 2030 (part of the [[30 by 30]] target).{{cite web |last1=Kim |first1=Juliana |last2=Treisman |first2=Rachel |title=What to know about the new U.N. high seas treaty – and the next steps for the accord |url=https://www.npr.org/2023/03/07/1161196476/un-high-seas-treaty-international-waters |website=NPR |access-date=9 March 2023}}{{cite web |last1=Flores |first1=Gaby |title=How people power helped protect the oceans |url=https://www.greenpeace.org/international/story/58596/how-people-power-helped-protect-oceans/ |website=Greenpeace |access-date=9 March 2023}} The treaty has articles regarding the principle "polluter-pays", and different impacts of human activities including areas beyond the national jurisdiction of the countries making those activities. The agreement was adopted by the 193 United Nations Member States.{{cite news |last1=Hemingway Jaynes |first1=Cristen |title=Newly Adopted UN High Seas Treaty Gives Ocean a 'Fighting Chance' |url=https://www.ecowatch.com/un-high-seas-treaty-2023.html |access-date=23 June 2023 |agency=Ecowatch |date=20 June 2023}} [503] => [504] => ==See also== [505] => {{portal|Oceans|Geography|Ecology|Environment}} [506] => * [[European Atlas of the Seas]] [507] => * [[Land and water hemispheres]] [508] => * [[List of seas]] [509] => * [[Marine heatwave]] [510] => * [[Ocean (disambiguation)]] [511] => * [[Ocean world]] [512] => * [[Planetary oceanography]] [513] => * [[World Ocean Atlas]] [514] => * [[World Oceans Day]] [515] => [516] => ==References== [517] => {{reflist|35em}} [518] => [519] => ==Further reading== [520] => * Peters, Kimberley, et al. eds. ''The Routledge Handbook of Ocean Space'' (2022), how experts in 32 fields study and interpret the oceans, [http://www.h-net.org/reviews/showrev.php?id=58336 onlne book review] [521] => [522] => ==External links== [523] => {{Sister project links|collapsible=yes|wikt=ocean|n=Category:Oceans|commonscat=yes|q=Oceans|s=no|v=no|b=no}} [524] => * [http://www.fao.org/fishery/en FAO (Food and Agriculture Organization of the United Nations) Fisheries Division] [525] => * [https://www.noaa.gov/ NOAA – National Oceanic and Atmospheric Administration (United States)] [526] => * [https://www.oceandecade.org/ United Nations Decade of Ocean Science for Sustainable Development (2021–2030)] [527] => [528] => [529] => {{Earth}} [530] => {{List of seas|state=uncollapsed}} [531] => {{Physical oceanography|expanded=other}} [532] => [533] => {{Authority control}} [534] => [535] => [[Category:Oceans| ]] [536] => [[Category:Oceanography|Oceans]] [537] => [[Category:Coastal and oceanic landforms]] [538] => [[Category:Bodies of water]] [539] => [[Category:Articles containing video clips]] [] => )
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Ocean

The Wikipedia page for "Ocean" provides an overview of this vast body of saltwater that covers most of Earth's surface. The page covers various aspects like definition, key features, exploration, importance, ecology, and human impacts on the oceans.

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The page covers various aspects like definition, key features, exploration, importance, ecology, and human impacts on the oceans. The page begins with a general definition of an ocean as a continuous expanse of saltwater that makes up around 71% of the planet's surface. It highlights the five major oceans: the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean. Each ocean is discussed in terms of its size, location, and unique characteristics. The page then delves into the key features of the oceans, which include their immense size, depth, and diverse topography. It explains how ocean currents are formed and their role in shaping climate patterns globally. The various zones of the ocean, such as the epipelagic, mesopelagic, bathypelagic, abyssopelagic, and hadalpelagic zones, are also described in detail. The exploration of the oceans and its history is explored next. The page covers the advancements in technology that have allowed humans to study and map the oceans in greater detail. It highlights famous expeditions, such as those conducted by Jacques Cousteau, and the discovery of unique marine ecosystems, like hydrothermal vents and coral reefs. The importance of the oceans is emphasized, as they play a crucial role in maintaining Earth's climate, regulating temperature, and driving weather patterns. The page also discusses the immense biodiversity present in the oceans, including various species of fish, marine mammals, and invertebrates. It highlights the delicate balance of marine ecosystems and the threats they face, such as pollution, overfishing, and climate change. Lastly, the page dives into the human impacts on the oceans, such as coastal development, marine pollution, and the extraction of resources like oil and gas. It also addresses conservation efforts, like the creation of marine protected areas and initiatives to reduce plastic waste. In conclusion, the Wikipedia page for "Ocean" provides a comprehensive overview of the Earth's vast saltwater bodies, covering their definition, key features, exploration, importance, ecological significance, and human impacts. It serves as a valuable resource for anyone seeking information about the world's oceans and their importance to our planet.

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Aluminium is a chemical element with the symbol Al and atomic number 13.

Antarctica

Antarctica is Earth's southernmost continent, located almost entirely within the Antarctic Circle.

Asia

Asia is the largest and most populous continent in the world, covering about 30% of the Earth's land area.

Atmosphere

Atmosphere is a comprehensive Wikipedia page that provides a thorough overview of Earth's atmosphere.

Bacteria

Bacteria are single-celled microorganisms that have a wide range of shapes and sizes.

Biodiversity

Biodiversity refers to the variety of life forms on Earth, encompassing the different species, ecosystems, and genetic variations that exist.

Calcium

Calcium is a chemical element with the symbol Ca and atomic number 20.

Climate

The Wikipedia page on climate provides a detailed overview of climate, including its definition, composition, and factors that influence it.

Cnidaria

Cnidaria is a phylum of marine animals that includes jellyfish, sea anemones, corals, and hydras.

Coral

Coral is a type of marine invertebrate that belongs to the phylum Cnidaria.

EARTH

Earth is the third planet from the Sun in our solar system and the only known celestial body to support life.

Earthquake

An earthquake is a natural occurrence that involves the shaking and trembling of the Earth's surface.

Ecosystem

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system.

Energy

Energy is the capacity to do work or produce heat.

Eukaryote

Eukaryotes are complex organisms whose cells contain a nucleus and other membrane-bound organelles.

Evaporation

Evaporation is a process by which a substance, usually in liquid form, transitions into a gaseous state.

Evolution

Evolution is a process that describes how living organisms have adapted and changed over time.

Fungi

Fungi are a diverse group of organisms that belong to the kingdom Fungi.

Mangrove

The Wikipedia page on mangroves provides an overview of these unique and highly valuable ecosystems.

Navigation

Navigation refers to the process of directing or guiding oneself through a physical or digital environment in order to reach a particular destination or desired outcome.

Nitrogen

Nitrogen is a chemical element with the symbol N and atomic number 7.

Nutrient

Nutrients are substances found in food that are essential for the growth, development, and maintenance of the body.

Oceanography

Oceanography is the scientific study of the world's oceans, including their physical and chemical properties, the biology and ecology of marine organisms, and the geology and geophysics of the ocean floor.

Oceans

Oxygen

Oxygen is a chemical element with the symbol O and atomic number 8.

Phosphorus

Phosphorus is a chemical element with the symbol P and atomic number 15.

Photosynthesis

Photosynthesis is a process in which green plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen.

Potassium

Potassium is a chemical element with the symbol K and atomic number 19.

Precipitation

Precipitation is a crucial aspect of Earth's water cycle and refers to any form of water that falls from the atmosphere to the Earth's surface.

Prokaryotes

Seagrass

Seagrasses are the only flowering plants which grow in marine environments.

Seawater

Seawater refers to the saline water found in the Earth's oceans and seas.

Ship

A ship is a large watercraft that is designed to navigate through the water, typically larger than a boat and capable of carrying cargo, passengers, or both.

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11.

Sun

The Sun is the star at the center of the Solar System, and it is by far the most important source of energy for life on Earth.

Water

Water is a transparent, odorless, tasteless liquid that covers around 71% of the Earth's surface and is the most abundant substance on the planet.

Whale

Whales are large, aquatic mammals belonging to the order Cetacea, which also includes dolphins and porpoises.