Editing Strait of Gibraltar (section)

===Inflow and outflow===
[[File:InternalWaves Gibraltar ISS009-E-09952 54.jpg|thumb|The Strait of Gibraltar with the Mediterranean Sea in upper right. [[Internal wave]]s (marked with arrows) are caused by water flowing through the Strait (bottom left, top right).]]

Water flows through the Strait more or less continuously, both eastwards and westwards. A smaller amount of deeper, saltier and therefore denser waters continually flow westwards (the [[Mediterranean outflow]]), while a larger amount of surface waters with lower salinity and density continually flow eastwards (the Mediterranean inflow). These general flow tendencies may be occasionally interrupted for brief periods by temporary tidal flows, depending on various lunar and solar alignments. The balance of the water flow is eastwards, since the evaporation rate within the Mediterranean basin is higher than the combined inflow of all the rivers that empty into it, plus the total precipitation of rain or snow that falls on it.<ref>{{Cite journal |last1=Soto-Navarro |first1=Javier |last2=Criado-Aldeanueva |first2=Francisco |last3=García-Lafuente |first3=Jesús |last4=Sánchez-Román |first4=Antonio |date=12 October 2010 |title=Estimation of the Atlantic inflow through the Strait of Gibraltar from climatological and in situ data |journal=Journal of Geophysical Research |language=en |volume=115 |issue=C10 |pages=C10023 |doi=10.1029/2010JC006302 |bibcode=2010JGRC..11510023S |issn=0148-0227 |doi-access=free |hdl=10630/29356 |hdl-access=free}}</ref> At the Strait's far western end is the [[Camarinal Sill]], the Strait's shallowest point which limits mixing between the cold, less saline Atlantic water and the warmer, more saline Mediterranean waters.

The Mediterranean waters are so much saltier than the Atlantic waters that they sink below the constantly incoming water and form a highly saline (''[[Thermohaline circulation|thermohaline]]'', both warm and salty) layer of bottom water. This layer of bottom-water constantly works its way out into the Atlantic as the Mediterranean outflow. On the Atlantic side of the Strait, a density boundary separates the Mediterranean outflow waters from the rest at about {{cvt|100|m|ft fathom}} depth. These waters flow out and down the continental slope, losing salinity, until they begin to mix and equilibrate more rapidly, much farther out at a depth of about {{cvt|1000|m|ft fathom}}. The Mediterranean outflow water layer can be traced for thousands of kilometres west of the Strait, before completely losing its identity.

[[File:Camarinal Still Water Mixing (Simplified).jpg|thumb|left|Simplifed and stylized diagram of currents at the [[Camarinal Sill]]]]
During the [[World War II|Second World War]], German [[U-boats]] used the currents to pass into the Mediterranean Sea without detection, by maintaining silence with engines off.<ref>Paterson, Lawrence (2007). ''U-Boats in the Mediterranean 1941–1944''. Chatham Publishing, pp. 19 and 182. {{ISBN|9781861762900}}</ref> From September 1941 to May 1944 Germany managed to send 62 U-boats into the Mediterranean. All these boats had to navigate the British-controlled Strait of Gibraltar where nine U-boats were sunk while attempting passage and 10 more had to break off their run due to damage.<ref>{{cite web |url=http://uboat.net/ops/mediterranean.htm |title=U-boat war in the Mediterranean |publisher=uboat.net |access-date=15 July 2011 |archive-date=3 August 2010 |archive-url=https://web.archive.org/web/20100803051504/http://www.uboat.net/ops/mediterranean.htm |url-status=live }}</ref>