The Strait of Sicily (also known as Sicilian Strait, Sicilian Channel, Channel of Sicily, Sicilian Narrows and Pantelleria Channel; it, Canale di Sicilia or the Stretto di Sicilia; scn, Canali di Sicilia or Strittu di Sicilia, ar, مضيق صقلية ' or ') is the
strait
A strait is an oceanic landform connecting two seas or two other large areas of water. The surface water generally flows at the same elevation on both sides and through the strait in either direction. Most commonly, it is a narrow ocean chan ...
between
Sicily
(man) it, Siciliana (woman)
, population_note =
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and
Tunisia
)
, image_map = Tunisia location (orthographic projection).svg
, map_caption = Location of Tunisia in northern Africa
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, capital = Tunis
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, ...
. The strait is about wide and divides the
Tyrrhenian Sea
The Tyrrhenian Sea (; it, Mar Tirreno , french: Mer Tyrrhénienne , sc, Mare Tirrenu, co, Mari Tirrenu, scn, Mari Tirrenu, nap, Mare Tirreno) is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenian pe ...
and the western
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...
, from the
eastern Mediterranean
Eastern Mediterranean is a loose definition of the eastern approximate half, or third, of the Mediterranean Sea, often defined as the countries around the Levantine Sea.
It typically embraces all of that sea's coastal zones, referring to commun ...
Sea. The maximum depth is .
Deep
currents in the strait flow from east to west, and the current nearer the surface travels from west to east. This unusual water flow is of interest to
oceanographer
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamic ...
s.
There are regular ferries between Sicily and Tunis across the Strait of Sicily.
The island of
Pantelleria
Pantelleria (; Sicilian: ''Pantiddirìa'', Maltese: ''Pantellerija'' or ''Qawsra''), the ancient Cossyra or Cossura, is an Italian island and comune in the Strait of Sicily in the Mediterranean Sea, southwest of Sicily and east of the Tunisi ...
lies in the middle of the strait.
![2-sill final](https://upload.wikimedia.org/wikipedia/commons/5/53/2-sill_final.png)
The Strait of Sicily is located between, at the eastern side,
Tunisia
)
, image_map = Tunisia location (orthographic projection).svg
, map_caption = Location of Tunisia in northern Africa
, image_map2 =
, capital = Tunis
, largest_city = capital
, ...
and the Malta Bank and on the northern side,
Sicily
(man) it, Siciliana (woman)
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, demographi ...
,
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
. Within the Central
Mediterranean sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...
it is one of the topographically complex regions. With a length of 600 km it connects the Eastern and Western Mediterranean basins. The strait is delimited by two systems; at the eastern side it is connected with the
Ionian Sea
The Ionian Sea ( el, Ιόνιο Πέλαγος, ''Iónio Pélagos'' ; it, Mar Ionio ; al, Deti Jon ) is an elongated bay of the Mediterranean Sea. It is connected to the Adriatic Sea to the north, and is bounded by Southern Italy, including ...
, south of the Malta Bank with a sill of 560 m deep, and, on the western side, two passages connect the strait with the Western Mediterranean basin. The passage or channel more closely to Sicily is narrow and around 430 m deep while the channel at the side of Tunisia is broader and shallower with a maximum depth of 365 m. Due to this particular
bathymetry
Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
with two different channels, the strait is called a "two-sill strait".
In the central region the strait is around 50 km to 100 km wide and 700 m to 900 m deep, but some parts consist of trenches of even 1800 m deep.
A
tunnel
A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...
is proposed to link Tunisia and Sicily as nowadays ferries cross the Strait regularly.
Flows
At the surface and in the upper 200 m the strait consists of an eastward flow provided by the Modified Atlantic Water (MAW). Underneath this eastward flow, the Levantine Intermediate Water (LIW) flows in westward direction. Just above the bottom of the Strait a relative small flow has been observed. This vein follows the same route as LIW but consists of different characteristics. The water flow is named 'transitional Eastern Mediterranean Deep Water' (tEMDW) and contains fresher, colder and denser (with a potential seawater density, ''σ
θ,'' of around 29.10) water than the LIW. In the
Ionian Sea
The Ionian Sea ( el, Ιόνιο Πέλαγος, ''Iónio Pélagos'' ; it, Mar Ionio ; al, Deti Jon ) is an elongated bay of the Mediterranean Sea. It is connected to the Adriatic Sea to the north, and is bounded by Southern Italy, including ...
it fills the transitional layer between the Eastern Mediterranean Deep Water and the LIW. This dense water exits the strait at a depth of 300 m at the sill and sinks down, because of its higher density than the LIW, till 1800 m when reaching the
Tyrrhenian Sea
The Tyrrhenian Sea (; it, Mar Tirreno , french: Mer Tyrrhénienne , sc, Mare Tirrenu, co, Mari Tirrenu, scn, Mari Tirrenu, nap, Mare Tirreno) is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenian pe ...
flowing along the Sicilian slope. This sharp sinking down of the dense water flow is a topic of interest among
oceanographers
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynami ...
. A second topic of interest regarding this little tEMDW flow is that it crosses the midline of the strait, more precisely the Malta sill. When the dense water flow reaches the western sill, it flows along the Tunisian coast instead of the Sicilian shelf. The water mass flows at a shallow depth of 300 m, while beneath the LIW, the tEMDW flows westward. Further downstream, the LIW has lower velocities and the dense water flow returns to the
geostrophic
A geostrophic current is an oceanic current in which the pressure gradient force is balanced by the Coriolis effect. The direction of geostrophic flow is parallel to the isobars, with the high pressure to the right of the flow in the Northern H ...
position located naturally along the Sicilian coast. Here the dense water sinks into the deeper ocean sea, around 1500 m–1850 m. This inversion of the interface slope is possible because the
buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...
and
Coriolis force
In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...
s are balancing each other in a so-called 'geostrophic balance' which is possible because of the flow velocities of both LIW and EMDW.
The tEMDW shows little variations in height, width and path and is thus geometrically quite stable.
Dynamics
The Central Mediterranean can be characterized by looking at differences in spatial and temporal scale. Three scales are common to use among oceanographers.
The first is the
mesoscale with a horizontal scale around ten kilometers and periods of days till a maximum of ten days. The sea can be influenced within the mesoscale by
wind stress
In physical oceanography and fluid dynamics, the wind stress is the shear stress exerted by the wind on the surface of large bodies of water – such as oceans, seas, estuaries and lakes. Stress is the quantity that describes the magnitude of a for ...
,
topography
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary sci ...
and by internal dynamical processes. Boundary currents and jets can be created by these processes which can evolve into
vortices
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
and filament patterns that can interact with large scale flows.
The second is the sub-basin scale with scales of 200 km till 300 km. This scale represents two dense water veins; the Atlantic Tunisian Current (ATC) which flows along the African coast and the Atlantic Ionian Stream (AIS) along the Sicilian coast. The AIS flows mainly eastward which can create
upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutr ...
on the Adventure Bank (AB) and the southern Sicilian coast. Upwelling is found to be the most intense during summer when the AIS is also relatively stronger than in other seasons. Due to the upwelling these coasts are of great interests of fishery. The ATC shows a specific path in winter while the route is less clearly-marked during summer.
The last common used scale is the large Mediterranean Basin scale which includes the
thermohaline circulation
Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective ''thermohaline'' derives from '' thermo-'' referring to temper ...
. The thermohaline circulation in the Strait of Sicily is anti-
estuarine
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
and is driven by, at one site, the fresh waters entering from the
Gibraltar Strait
The Strait of Gibraltar ( ar, مضيق جبل طارق, Maḍīq Jabal Ṭāriq; es, Estrecho de Gibraltar, Archaic: Pillars of Hercules), also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Medit ...
and on the other side, the negative freshwater budget from the
Mediterranean Basin
In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and w ...
.
Also the westward LIW in the intermediate layer and less saltier eastward
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
water on top are considered in this scale.
The outflow of dense-water-masses characteristics of the Strait of Sicily are not stable but have been found to change interannually. Also the thermohaline circulation showed changes in structure and
stratification
Stratification may refer to:
Mathematics
* Stratification (mathematics), any consistent assignment of numbers to predicate symbols
* Data stratification in statistics
Earth sciences
* Stable and unstable stratification
* Stratification, or st ...
. These changes were caused by deep water formed in the
Aegean Sea
The Aegean Sea ; tr, Ege Denizi (Greek language, Greek: Αιγαίο Πέλαγος: "Egéo Pélagos", Turkish language, Turkish: "Ege Denizi" or "Adalar Denizi") is an elongated embayment of the Mediterranean Sea between Europe and Asia. It ...
which replaced the water formed in the
Adriatic
The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) ...
during the 1990s. This dense water caused enhanced salinity and temperatures in the Aegean Sea for a few years creating the deep/mediate Mediterranean overturning perturbation which has been given the name of Eastern Mediterranean Transient (EMT). The EMT is the major perturbation of the circulation and water mass aspects in this area since systematic observational data is available (1950s). The effect of the EMT on the Strait of Sicily was a freshening of the surface waters.
Another important circulation mechanism that exists in the Strait of Sicily is the Biomodal Oscillating System (BiOS)
Which is a
feedback mechanism
Feedback occurs when outputs of a system are routed back as inputs as part of a Signal chain (signal processing chain), chain of Causality, cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. ...
between the Ionic and the Adriatic sea. The thermohaline properties of the Adriatic Sea show quasi-decadal oscillations that are related to the circulation of the Ionian Sea. The upper-layer of the northern Ionian Sea shows circulations that vary between a
cyclonic
In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anti ...
movement, corresponding advection of waters from the Eastern Mediterranean with very saline waters and low nutrients (
oligotroph
An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of ...
ic water), and anticyclonic movement which results in saline and
copiotroph A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations.
Copiotrophic organisms tend to grow in high organic substrate condi ...
(nutrient-rich) waters from the Western Mediterranean towards the Adriatic. The density of the dense waters that flow from the Adriatic Sea into the northern Ionian Sea highly depends on the type of circulation (cyclonic, or anticyclonic) in the Ionian Sea and at the other hand influences the
vorticity
In continuum mechanics, vorticity is a pseudovector field that describes the local spinning motion of a continuum near some point (the tendency of something to rotate), as would be seen by an observer located at that point and traveling along wit ...
in the Ionian Sea itself resulting in a feedback mechanism. BiOS is one of the dominant mechanisms influencing biochemical processes in the Adriatic and therefore has great impact on the organisms within this sea and in the strait.
Levantine intermediate water circulation
Through the strait of Sicily passes the Levantine Intermediate Water (LIW). The LIW is a westward flowing water mass in the intermediate layers (from 200 m till 400 m) formed in the
Levantine basin
The Levantine Sea (Arabic: بحر الشام, tr, Levanten Denizi, el, Θάλασσα του Λεβάντε) is the easternmost part of the Mediterranean Sea.
Geography
The Levantine Sea is bordered by Turkey in the north and north-east co ...
, the most eastern part of the Mediterranean sea and ending in the
strait of Gibraltar
The Strait of Gibraltar ( ar, مضيق جبل طارق, Maḍīq Jabal Ṭāriq; es, Estrecho de Gibraltar, Archaic: Pillars of Hercules), also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Medi ...
and the
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
. The LIW is characterized by high
salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
and temperature. This high salinity concentrations is one of the important factors for the formation of the deep water in the Southern Adriatic and the
Gulf of Lion
The Gulf of Lion or Gulf of Lions ( French: ''golfe du Lion'', Spanish: ''golfo de León'', Italian: ''Golfo del Leone'', Occitan: ''golf del/dau Leon'', Catalan: ''golf del Lleó'', Medieval Latin: ''sinus Leonis'', ''mare Leonis'', Classical L ...
s.
During the past years (measured from 1993 till 1998) the potential temperature and salinity of the LIW have decreased significantly. This change in thermohaline properties of the LIW is in agreement with another event that occurred in the 1990s which is the uplifting of the colder and less saline deep waters in the Eastern Mediterranean referred as the Eastern Mediterranean Transient (EMT).
Migrants
Pantelleria
Pantelleria (; Sicilian: ''Pantiddirìa'', Maltese: ''Pantellerija'' or ''Qawsra''), the ancient Cossyra or Cossura, is an Italian island and comune in the Strait of Sicily in the Mediterranean Sea, southwest of Sicily and east of the Tunisi ...
is an Italian island located in the Strait of Sicily around 64 km from Tunisia. Nowadays the island is one of the destinations migrants, mostly from Tunisia, try to reach. Sometimes over 200 people in only two days cross the strait in little boats.
Winds
The winds that are found above the Strait of Sicily are the two Mediterranean winds:
Sirocco
Sirocco ( ), scirocco, or, rarely, siroc (see below) is a Mediterranean wind that comes from the Sahara and can reach hurricane speeds in North Africa and Southern Europe, especially during the summer season.
Names
''Sirocco'' derives from ...
, bringing dry and warm air from the South East and
Mistral
Mistral may refer to:
* Mistral (wind) in southern France and Sardinia
Automobiles
* Maserati Mistral, a Maserati grand tourer produced from 1963 until 1970
* Nissan Mistral, or Terrano II, a Nissan 4×4 produced from 1993 until 2006
* Microp ...
, bringing cold air from the northwest.
Biology
The Strait of Sicily is rich in biodiversity due to its different water currents. Also its geographical position between the Eastern and Western Mediterranean contributes to the high ecological importance of the strait. Warm temperature and tropical species from the
Lavantin basin cross the strait. The vast variety in species cannot only be found near the surface and coasts but also the deep water contains communities of vulnerable species as the
Scleractinia
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyp (zoology), polyps and have a cylindrical body crowned by an oral di ...
,
Antipatharians,
gorgonia
''Gorgonia'' is a genus of soft corals, sea fans in the family Gorgoniidae.
Species
The World Register of Marine Species lists these species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, ...
ns and
red corals.
The habitat of one of the corals in the strait, the
Corallium rubrum
Precious coral, or red coral, is the common name given to a genus of marine corals, ''Corallium''. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink-orange skeleton, which is used for m ...
, family of the
Coralliidae
Coralliidae, also known as precious corals, is a taxonomic family of soft corals belonging to the phylum Cnidaria of the family Scleraxonia. These sessile corals are one of the most dominant members of hard-bottomed benthic environments such as ...
(
Anthozoa
Anthozoa is a subphylum of marine invertebrates which includes the sea anemones, Scleractinia, stony corals and Alcyonacea, soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plank ...
,
Gorgonacea) is between a few meters to 120 meters deep. Its bright red calcific axis has been used for jewelry from ancient times. Although extinction of these corals is not the case yet because of high productivity in this ecosystem, a decline has been observed in the shallow waters.
These corrals are part of an initiative of worldwide conservation. During the Conference of the Parties of CITES number 14 (CoP14) two workshops were decided to be organized about the corals in the Pacific and Mediterranean.
Among the species that are fished at high rates, are the
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
family. These
mollusca
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
ns, especially the species O. Vulgaris, are of interest both for industrial and artisanal fisheries.
Due to high biodiversity, productivity rates and importance of the different species for the ecosystem, the Mediterranean Sea and the Strait of Sicily are becoming of more interest for researchers during the recent years.
Also regarding the current
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, information can be gained by researching the changes in biodiversity in the Strait of Sicily.
Volcanic activity
![Sicily Tectonic Plates](https://upload.wikimedia.org/wikipedia/commons/6/6d/Sicily_Tectonic_Plates.png)
Due to the natural position of the Strait of Sicily, above the conjunction of the
Eurasian
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...
and
African
African or Africans may refer to:
* Anything from or pertaining to the continent of Africa:
** People who are native to Africa, descendants of natives of Africa, or individuals who trace their ancestry to indigenous inhabitants of Africa
*** Ethn ...
tectonic plate, volcanic activity occurs in the strait.
The volcanic activity is mainly focused on the islands
Pantelleria
Pantelleria (; Sicilian: ''Pantiddirìa'', Maltese: ''Pantellerija'' or ''Qawsra''), the ancient Cossyra or Cossura, is an Italian island and comune in the Strait of Sicily in the Mediterranean Sea, southwest of Sicily and east of the Tunisi ...
and
Linosa
Linosa (; scn, Linusa; ar, نموشة, ''Nammūša'') is one of the Pelagie Islands in the Sicily Channel of the Mediterranean Sea.
The island is a part of the Italian comune of Lampedusa e Linosa, part of the province of Agrigento in Sicily, ...
. A climax in volcanic activity was found in the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
. Although minor submarine eruptions can still be found, mostly located on the seafloor along the northwest and southeast regional faults.
During historical times some
seamount
A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...
s did erupt while other seamounts have been covered by Pliocene-Quaternary sediments.
The submarine volcanoes are located in the Adventure Plateau, Graham and Nameless Banks. In 1831 a submarine volcano erupted on the Graham Bank at a depth of around 200 m. This eruption gave rise to the
Graham Island
Graham Island () is the largest island in the Haida Gwaii archipelago (previously known as the Queen Charlotte Islands), lying off the mainland coast of British Columbia, Canada. It is separated by the narrow Skidegate Channel from the other pri ...
65 m above sea level. Also in the year 1863 this volcano erupted, whereas the youngest eruption in the region was in 1891 around 5 km north of Pantelleria. At the southeast of Graham Bank, at the Pinne Bank an emission was observed in 1941.
See also
*
Italy–Tunisia Delimitation Agreement
The Italy–Tunisia Delimitation Agreement is a 1971 treaty between Italy and Tunisia in which the two countries agreed to delimit a maritime boundary between them in the continental shelf. The text of the treaty sets out a complex boundary in t ...
References
External links
*
{{Authority control
Geography of Sicily
Sicily
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Sicily
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Bodies of water of Tunisia
Straits of the Mediterranean Sea
Italy–Tunisia border
International straits