Editing Upwelling (section)

=== Coastal ===
Coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive [[fisheries]] in the world. Coastal upwelling will occur if the wind direction is parallel to the coastline and generates wind-driven currents. The wind-driven currents are diverted to the right of the winds in the Northern Hemisphere and to the left in the Southern Hemisphere due to the [[Coriolis effect]].  The result is a net movement of surface water at right angles to the direction of the wind, known as the [[Ekman transport]] (See also [[Ekman Spiral]]). When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water.<ref name="Mann"/> Normally, this upwelling process occurs at a rate of about 5–10 meters per day, but the rate and proximity of upwelling to the coast can be changed due to the strength and distance of the wind.<ref name="Anderson"/><ref name="Nelson">{{cite journal | last1 = Bakun | first1 = A | last2 = Nelson | first2 = CS | year = 1991 | title = The seasonal cycle of wind-stress curl in subtropical eastern boundary current regions | journal = Journal of Physical Oceanography | volume = 21 | issue = 12| pages = 1815–1834 | doi=10.1175/1520-0485(1991)021<1815:tscows>2.0.co;2| bibcode = 1991JPO....21.1815B | doi-access = free }}</ref>

Deep waters are rich in nutrients, including [[nitrate]], [[phosphate]] and [[silicic acid]], themselves the result of [[decomposition]] of sinking [[organic matter]] (dead/detrital plankton) from surface waters. When brought to the surface, these nutrients are utilized by [[phytoplankton]], along with dissolved CO<sub>2</sub> ([[carbon dioxide]]) and light energy from the [[sun]], to produce [[organic compound]]s, through the process of [[photosynthesis]].  Upwelling regions therefore result in very high levels of primary production (the amount of carbon fixed by [[phytoplankton]]) in comparison to other areas of the ocean. They account for about 50% of global marine productivity.<ref name="Blanchette">{{cite journal | last1 = Blanchette | first1 = CA |author-link1=Carol Blanchette| last2 = Wieters | first2 = EA | last3 = Briotman | first3 = BR | last4 = Kinlan | first4 = BP | last5 = Schiel | first5 = DR | year = 2009 | title = Trophic structure and diversity in rocky intertidal upwelling ecosystems: a comparison of community patterns across California, Chile, South Africa, and New Zealand | journal = Progress in Oceanography | volume =  83| issue = 1–4| pages =  107–116| doi = 10.1016/j.pocean.2009.07.038 | bibcode = 2009PrOce..83..107B }}</ref>  High primary production propagates up the [[food chain]] because [[phytoplankton]] are at the base of the oceanic food chain.<ref name="Lalli">Lalli, C.M., Parsons, T.R. (1997) "Biological Oceanography: An Introduction" Oxford: Elsevier Publications. {{ISBN|0-7506-3384-0}}</ref>

The food chain follows the course of:

* Phytoplankton → [[Zooplankton]] → Predatory zooplankton → [[Filter feeders]] → Predatory fish<ref name="Mann"/> → Marine birds, marine mammals<ref name="Brodeur">{{cite journal | last1 = Brodeur | first1 = RD | last2 = Ware | first2 = DM | year = 2007 | title = Long-term variability in zooplankton biomass in the subarctic Pacific ocean | journal = Fisheries Oceanography | volume = 1 | issue = 1| pages = 32–38 | doi = 10.1111/j.1365-2419.1992.tb00023.x }}</ref>

Coastal upwelling exists year-round in some regions, known as ''major coastal upwelling systems'', and only in certain months of the year in other regions, known as ''seasonal coastal upwelling systems''. Many of these upwelling systems are associated with relatively high carbon productivity and hence are classified as [[Large marine ecosystem|Large Marine Ecosystems]].<ref name="Kampf">Kämpf J., Chapman P. (2016) "Upwelling Systems of the World" Cham: Springer International Publishing AG. {{ISBN|978-3-319-42524-5}}</ref>

Worldwide, there are five major coastal currents associated with upwelling areas: the [[Canary Current]] (off [[Northwest Africa]]), the [[Benguela Current]] (off [[southern Africa]]), the [[California Current]] (off [[California]] and [[Oregon]]), the [[Humboldt Current]] (off [[Peru]] and [[Chile]]), and the [[Somali Current]] (off [[Somalia]] and [[Oman]]).  All of these currents support major fisheries.  The four major eastern boundary currents in which coastal upwelling primarily occurs are the Canary Current, Benguela Current, California Current, and Humboldt Current.<ref name="Cury">{{cite journal | last1 = Cury | first1 = P | last2 = Bakun | first2 = A | last3 = Crawford | first3 = RJM | last4 = Jarre | first4 = A | last5 = Quinones | first5 = RA | last6 = Shannon | first6 = LJ | last7 = Verheye | first7 = HM | year = 2000 | title = Small pelagics in upwelling systems: patterns of interaction and structural changes in "wasp-waist" ecosystems | journal = ICES Journal of Marine Science | volume = 57 | issue = 3| pages = 603–618 | doi=10.1006/jmsc.2000.0712| doi-access = free | bibcode = 2000ICJMS..57..603C }}</ref>  The [[Benguela Current]] is the eastern boundary of the [[South Atlantic Gyre|South Atlantic subtropical gyre]] and can be divided into a northern and southern sub-system with upwelling occurring in both areas.  The subsystems are divided by an area of permanent upwelling off of [[Luderitz]], which is the strongest upwelling zone in the world.  The [[California Current|California Current System]] (CCS) is an eastern boundary current of the North Pacific that is also characterized by a north and south split.  The split in this system occurs at [[Point Conception]], California due to weak upwelling in the South and strong upwelling in the north.  The [[Canary Current]] is an eastern boundary current of the [[North Atlantic Gyre]] and is also separated due to the presence of the [[Canary Islands]].  Finally, the [[Humboldt Current]] or the Peru Current flows west along the coast of [[South America]] from [[Peru]] to [[Chile]] and extends up to 1,000 kilometers offshore.<ref name="Blanchette"/>  These four eastern boundary currents comprise the majority of coastal upwelling zones in the oceans.

==== Equatorial ====
[[File:Equatorial upwelling zone in the Pacific ocean.gif|thumb|300px|right|{{center|Effects of equatorial upwelling on surface chlorophyll concentrations in the [[Pacific Ocean]]}}]]

Upwelling at the [[equator]] is associated with the [[Intertropical Convergence Zone]] (ITCZ) which actually moves, and consequently, is often located just north or south of the equator. Easterly (westward) [[trade wind]]s blow from the Northeast and Southeast and converge along the equator blowing West to form the ITCZ.  Although there are no Coriolis forces present along the equator, upwelling still occurs just north and south of the equator. This results in a divergence, with denser, nutrient-rich water being upwelled from below, and results in the remarkable fact that the equatorial region in the [[Pacific]] can be detected from space as a broad line of high [[phytoplankton]] concentration.<ref name="Jennings"/>

==== Southern Ocean ====
[[File:Antarctic bottom water.svg|thumb|300px|{{center|Upwelling in the [[Southern Ocean]]}}]]
Large-scale upwelling is also found in the [[Southern Ocean]]. Here, strong westerly (eastward) winds blow around [[Antarctica]], driving a significant flow of water northwards. This is actually a type of coastal upwelling.  Since there are no continents in a band of open latitudes between [[South America]] and the tip of the Antarctic Peninsula, some of this water is drawn up from great depths. In many numerical models and observational syntheses, the Southern Ocean upwelling represents the primary means by which deep dense water is brought to the surface. In some regions of Antarctica, wind-driven upwelling near the coast pulls relatively warm [[Circumpolar deep water]] onto the continental shelf, where it can enhance ice shelf melt and influence ice sheet stability.<ref>{{Cite journal|last1=Greene|first1=Chad A.|last2=Blankenship|first2=Donald D.|last3=Gwyther|first3=David E.|last4=Silvano|first4=Alessandro|last5=Wijk|first5=Esmee van|date=2017-11-01|title=Wind causes Totten Ice Shelf melt and acceleration|journal=Science Advances|language=en|volume=3|issue=11|pages=e1701681|doi=10.1126/sciadv.1701681|issn=2375-2548|pmc=5665591|pmid=29109976|bibcode=2017SciA....3E1681G}}</ref> Shallower, wind-driven upwelling is also found in off the west coasts of North and South America, northwest and southwest Africa, and southwest and [[Great South Australian Coastal Upwelling System|south Australia]], all associated with oceanic subtropical high pressure circulations (see coastal upwelling above).

Some models of the ocean circulation suggest that broad-scale upwelling occurs in the tropics, as pressure driven flows converge water toward the low latitudes where it is diffusively warmed from above. The required diffusion coefficients, however, appear to be larger than are observed in the real ocean. Nonetheless, some diffusive upwelling does probably occur.

====Other sources====
* Local and intermittent upwellings may occur when offshore islands, [[ridges]], or [[seamounts]] cause a deflection of deep currents, providing a nutrient rich area in otherwise low productivity ocean areas.  Examples include upwellings around the [[Galapagos Islands]] and the [[Seychelles Islands]], which have major [[pelagic]] fisheries.<ref name="Jennings"/>
* Upwelling could occur anywhere as long as there is an adequate shear in the horizontal wind field. For example when a [[tropical cyclone]] transits an area, usually when moving at speeds of less than 5&nbsp;mph (8&nbsp;km/h). The cyclonic winds cause a divergence in the surface water in the Ekman layer, that turn requires upwelling of deeper water to maintain continuity.<ref>{{cite book |last1=Knauss |first1=J.A |title=Introduction to Physical Oceanography |date=1997 |publisher=Waveland Press, Inc. |isbn=978-1-57766-429-1}}</ref>
* Artificial upwelling is produced by devices that use ocean wave energy or ocean thermal energy conversion to pump water to the surface. Ocean wind turbines are also known to produce upwellings.<ref>https://wiki.met.no/_media/windfarms/brostrom_jms_2008.pdf On the influence of large wind farms on the upper ocean circulation. Göran Broström, Norwegian Meteorological Institute, Oslo, Norway</ref>  Ocean wave devices have been shown to produce plankton blooms.<ref>[http://oregonstate.edu/dept/ncs/newsarch/2008/Sep08/artificialupwelling.html US Research project, NSF and Oregon State University] {{webarchive |url=https://web.archive.org/web/20090804092457/http://oregonstate.edu/dept/ncs/newsarch/2008/Sep08/artificialupwelling.html |date=August 4, 2009 }}</ref>