# Retroflect

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> Source: https://en.wikipedia.org/wiki/Retroflect
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{{Short description|Movement of an ocean current that doubles back on itself}}
'''Retroflection''' is the movement of an ocean current that doubles back on itself.

==Usage history==
More commonly used to describe the way the mammalian [intestine](/source/intestine) or [uterus](/source/uterus) might turn back on itself, retroflection was first used in an oceanographic sense in 1970 by South African oceanographer [Nils Bang](/source/Nils_Bang), to describe the [Agulhas Current](/source/Agulhas_Current)<ref>{{Cite journal
 | last = Lutjeharms | first = J. R. E.
 | title = Three decades of research on the greater Agulhas Current
 | year = 2006 | journal = Ocean Sci. Discuss. | volume = 3 | pages = 939–995
 | oclc = 800498605| url = https://hal.archives-ouvertes.fr/docs/00/29/84/02/PDF/osd-3-939-2006.pdf}}</ref> which curves on itself at the southern tip of Africa to become the Aghulhas Return Current.<ref>{{Cite journal
 | last = Bang | first = N. D.
 | title = Dynamic interpretations of a detailed surface temperature chart of the Agulhas Current retroflection and fragmentation area
 | year = 1970 | journal = South African Geographical Journal | volume = 52 | pages = 67–76
 | doi = 10.1080/03736245.1970.10559466}}</ref> Bang credited the inspiration for the metaphor to his wife, Alison Coombe Bang, a nursing sister, who mentioned the term during her midwifery studies. Bang's research, through the University of Cape Town, was done on a limited budget and with rudimentary equipment,<ref name="SDB-1977">Sciendaba, Vol XII No 48, 15 December 1977</ref> yet his studies using closely spaced [bathythermograph](/source/bathythermograph) readings, were later corroborated by satellite thermal imagery. The term was then revived<ref>{{Cite journal
 | last = Lutjeharms | first = J. R. E
 | title = Features of the southern Agulhas Current circulation from satellite remote sensing
 | year = 1981 | journal = South African Journal of Science | volume = 77 | pages = 231–236}}</ref> and is now common parlance among oceanographers. The Agulhas current's retroflection is now key to an understanding of its dynamics.<ref name="SDB-1977" />

==Retroflection regions==
The [North Brazil Current](/source/North_Brazil_Current) (NBC) is a western [boundary current](/source/boundary_current) that flows off the coast of northeast Brazil, in the tropical Atlantic that transports upper ocean waters across the equator. It retroflects between 4°N and 10°N. Particularly during summer and fall, the NBC retroflects from the coast at 6° to 7°N and feeds the [North Equatorial Countercurrent](/source/Equatorial_Counter_Current) and [North Equatorial Undercurrent](/source/Equatorial_Undercurrent). The NBC sheds large anticyclonic rings that move northwestward along the [continental break](/source/continental_break). (Didden and Schott, 1993). These warm rings could play an important role in the net meridional transport of warm water in the upper layers of the Atlantic Ocean as part of the [meridional overturning circulation](/source/meridional_overturning_circulation) (MOC).<ref name=NBC-1>
{{Include-NOAA}}
*{{Cite web
  | title =Long Term Time Series of Surface Currents, North Brazil Current 
  | publisher =NOAA-AOML 
  | date =June 8, 2007 
  | url =https://www.aoml.noaa.gov/phod/altimetry/cvar/nbc/index.php 
  | format =Online (website) 
  | accessdate =2011-05-28}} </ref><ref name=NBC-2>
{{Include-NOAA}}  
*{{Cite web
  | title =North Brazil Current 
  | publisher =NOAA-AOML 
  | url =http://www.aoml.noaa.gov/phod/benchmarks/North%20Brazil%20Current/NBC%20Sept.html 
  | format =Online (website)
  | accessdate =2011-05-28}}</ref>

In the southeast [Atlantic Ocean](/source/Atlantic_Ocean) the current ''retroflects'' (turns back on itself) in the Agulhas Retroflection due to shear interactions with the strong [Antarctic Circumpolar Current](/source/Antarctic_Circumpolar_Current).  This water becomes the [Agulhas Return Current](/source/Agulhas_Return_Current), rejoining the [Indian Ocean Gyre](/source/Indian_Ocean_Gyre). It is estimated that up to 85 Sv ([Sverdrup](/source/Sverdrup)s) of the net transport is returned to the [Indian Ocean](/source/Indian_Ocean) through the retroflection.  The remaining water is transported into the [South Atlantic Gyre](/source/South_Atlantic_Gyre) in the Agulhas Leakage.  Along with direct branch currents, this leakage takes place in surface water filaments, and Agulhas Eddies.<ref>This paragraph is copied from the section entitled ''Retroflection'' in the Wikipedia article entitled [Agulhas Current](/source/Agulhas_Current). This for attribution only and it is not considered a reliable source.</ref>

==References==
{{Reflist}}
Category:Oceans
Category:Ocean currents
Category:Wikipedia articles incorporating text from NOAA

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Adapted from the Wikipedia article [Retroflect](https://en.wikipedia.org/wiki/Retroflect) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Retroflect?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.