Black Sea

For other uses, see Black Sea (disambiguation).

Map of the Black Sea

Illustration of the Black Sea

Template:FixHTML The Black Sea is an inland sea between southeastern Europe and the Anatolian peninsula (Turkey) and is ultimately connected to the Atlantic Ocean via the Mediterranean and Aegean Seas and various straits. The Bosporus strait connects it to the Sea of Marmara, then the long island-bound strait of the Dardenelles to the Aegean Sea region of the Mediterranean. These waters separate eastern Europe and western Asia. The Black sea is also connected to the Sea of Azov by the Strait of Kerch.

The Black Sea has an area of Template:Km2 to mi2, and a maximum depth of 2,200 m (7,200 ft).) Like the Mediterranean Sea, there is a net inflow of seawater through the Bosporus into the oceanic region of some Template:Km3 to mi3 per year, that is lost to evaporation or into geologic faults and so gradually raises the salinity. Freshwater flows in from the surrounding areas, especially central and middle-eastern Europe, Template:Km3 to mi3 per year. The most important river entering the Black Sea is the Danube.

Countries bordering the Black Sea are Turkey, Romania, Bulgaria, Ukraine, Russia, and Georgia. The Crimean peninsula is an autonomous republic of Ukraine. Russia leases a navy base in Sevastopol from Ukraine as a result of the partition of the Black Sea Fleet after the fall of the Soviet Union. The lease of the navy base by Russia in Sevastopol is set to expire in 2017, and is not scheduled for renewal.

Important cities along the coast include: Constanţa (metropolitan area of 550,000 and urban area of 650,000), Mangalia (41,153), Burgas (229,250), Varna (357,752) , Odessa (1,001,000), Kherson (358,000), Sevastopol (379,200), Yalta (80,552), Kerch (158,165), Novorossiysk (281,400), Sochi (328,809), Sukhumi (43,700), Poti (47,149), Batumi (121,806), Trabzon (275,137), Samsun (439,000) and Zonguldak (104,276).

Name

Modern names of the Sea are equivalents of the English name, "Black Sea", including Greek Mavre Thalassa (Μαύρη Θάλασσα), Bulgarian Cherno more (Черно море), Georgian Shavi zghva (შავი ზღვა), Laz Ucha Zuğa, or simply Zuğa 'Sea', Romanian Marea Neagră, Russian Chyornoye more (Чёрное море), Turkish Karadeniz, Ukrainian Chorne more (Чорне море), Ubykh /ʃʷaʤa/. This name cannot be traced to an earlier date than the thirteenth century, but there are indications that it may be considerably older.

Strabo's Geography (1.2.10) reports that in antiquity, the Black Sea was often just called "the Sea" (ho pontos). For the most part, Graeco-Roman tradition refers to the Black Sea as the 'Hospitable sea', Euxeinos Pontos (Εὔξεινος Πόντος). This is a euphemism replacing an earlier 'Inhospitable Sea', Pontos Axeinos, first attested in Pindar (early fifth century BCE,~475 BC). Strabo (7.3.6) thinks that the Black Sea was called "inhospitable" before Greek colonization because it was difficult to navigate, and because its shores were inhabited by savage tribes; and that the name was changed to "hospitable" after the Milesians had colonized, making it part of Greek civilization. It is also possible that the name Axeinos arose by popular etymology from an Iranian axšaina- 'dark'; the designation "Black Sea" may thus date from Antiquity. The reason for the name may be an ancient assignment of colours to the direction of the compass — black referring to the north, and red referring to the south. Herodotus on one occasion uses Red Sea and Southern Sea interchangeably.

Another possible explanation comes from the colour of the Black Sea's deep waters. Being further north than the Mediterranean Sea and much less saline, the microalgae concentration is much richer, causing the dark colour. Visibility in the Black Sea is on average approximately five meters (5.5 yd), as compared to up to thirty-five meters (38 yd) in the Mediterranean.

One Bulgarian understanding of the name is that the sea used to be quite stormy. Some sources stipulate that it goes back to the time of Noah's Ark. The Black Sea deluge theory is based on that idea.

In naval science, the Black Sea is thought to have received its name because of its hydrogen sulfide layer that begins about 200 meters below the surface, and that ends all life from that point downward.

Geology and bathymetry

Bay of Sudak.

The Black Sea forms an enclosed basin, located between south-eastern Europe and Asia Minor. The basin was formed during the Miocene orogenies which uplifted the mountain ranges and divided the ancient Tethys Ocean into several brackish basins, including the Sarmatic Sea. The Caspian, Azov, Aral and Black Seas are the remnants of this evaporated basin.

The basin is divided into two sub-basins by a convexity extending south from the Crimean peninsula. The north-west of the basin is characterized by a relatively large shelf up to 190 km (120 mi) wide, which has a relatively shallow apron with gradients between 1:40 and 1:1000. The southern edge around Turkey and the eastern edge around Georgia, however, are typified by a shelf that rarely exceeds 20 km (12 mi) in width and an apron that is typically 1:40 gradient with numerous submarine canyons and channel extensions. The Euxine abyssal plain in the centre of the Black Sea reaches a maximum depth of 2,206 m (7,238 ft) just south of Yalta on the Crimean peninsula. The basin is connected to the Mediterranean Sea via the Turkish Straits System (TSS) in the south-west, which includes the Bosporus and Dardanelles straits and the Sea of Marmara. The Black Sea is connected to the Sea of Azov in the north-east via the Kerch straits.

Hydrology and hydrochemistry

Satellite view of the Black Sea, taken by NASA MODIS.

The Black Sea is the world’s largest meromictic basin where the deep waters do not mix with the upper layers of water that receive oxygen from the atmosphere. As a result, over 90% of the deeper Black Sea volume is anoxic water. The current hydrochemical configuration is primarily controlled by basin topography and fluvial inputs, which result in a strongly stratified vertical structure and a positive water balance. The upper layers are generally cooler, less dense and less salty than the deeper waters, as they are fed by large fluvial systems, whereas the deep waters originate from the warm, salty waters of the Mediterranean. This influx of dense water from Mediterranean is balanced by an outflow of fresher Black Sea surface-water into the Marmara Sea, maintaining the stratification and salinity levels.

The surface water has an average salinity of 18 to 18.5 parts per thousand (compared to 30 to 40 for the oceans) and contains oxygen and other nutrients required to sustain biotic activity. These waters circulate in a basin-wide anti-cyclonic shelfbreak gyre known as the Rim Current which transports water round the perimeter of the Black Sea. Within this feature, two smaller cyclonic gyres operate, occupying the eastern and western sectors of the basin. Outside the Rim Current, numerous quasi-permanent coastal eddies are formed due to upwelling around the coastal apron and ‘wind curl’ mechanisms. The intra-annual strength of these features is controlled by seasonal atmospheric and fluvial variations. Sea Surface Temperature of the surface waters varies seasonally from 8 °C (46 °F) to 30 °C (86 °F).

Directly beneath the surface waters the Cold Intermediate Layer (CIL) is found. This layer is composed of cool, salty surface waters, which are the result of localised atmospheric cooling and decreased fluvial input during the winter months. The production of this water is focussed in the centre of the major gyres and on the NW shelf and as the water is not dense enough to penetrate the deep waters, isopycnal advection occurs, dispersing the water across the entire basin. The base of the CIL is marked by a major thermocline, halocline and pycnocline at ~100-200 m and this density disparity is the major cause of deep-water isolating.

Below the pycnocline, salinity increases to 22 to 22.5 ppt and temperatures rise to around 8.5 °C (47.3 °F). The hydrochemical environment shifts from oxygenated to anoxic, as bacterial decomposition of sunken biomass utilises all of the free oxygen. Certain species of extremophile bacteria are capable of using sulfate (SO₄²⁻) in the oxidation of organic material, which leads to the creation of hydrogen sulfide (H₂S). This enables the precipitation of sulfides such as iron-sulphides like pyrite, greigite and iron-monosulphide as well as the dissolution of carbonate matter such as Calcium carbonate (CaCO₃) found in shells. Organic matter, including anthropogenic artefacts such as boat hulls, are well preserved. During periods of high surface productivity, short-lived algal blooms cause organic rich layer known as sapropels to occur. Scientists have reported an annual phytoplankton bloom that can be seen in many NASA images of the region.

Another danger to people posed by the anoxic layer could come from a small asteroid's impact into the Black Sea. Recently modelling shows there is a significant threat to life for people living on the sea's shore.

Fauna

• 
  Jellyfish, near Romanian coast.
• 
  Actinia, near Romanian coast.
• 
  Actinia, near Romanian coast.
• 
  Goby, near Romanian coast.
• 
  Stingray, near Romanian coast.
• 
  Goat fish, near Romanian coast.
• 
  Hermit crab, near Romanian coast.
• 
  Blue sponge (?), near Romanian coast.
• 
  Spiny Dogfish (Black Sea Sharks at Risk)

Mediterranean connection during the Holocene

The Bosporus, taken from the ISS.

Map of the Dardanelles.

While it is agreed that the Black Sea has been a freshwater lake (at least in upper layers) with a considerably lower level during the last glaciation, its post glacial development into a marine sea is still a subject of intensive study and debate. There are catastrophic scenarios such as put forward by William Ryan and Walter Pitman as well as models emphasizing a more gradual transition to saline conditions and transgression in the Black Sea.

They are based on different theories about the level the freshwater lake had reached by the time the Mediterranean Sea was high enough to flow over the Dardanelles and the Bosporus. On the other hand, a study of the sea floor on the Aegean side shows that in the 8th millennium BC there was a large flow of fresh water out of the Black Sea.

In a series of expeditions, a team of marine archaeologists led by Robert Ballard identified what appeared to be ancient shorelines, freshwater snail shells, drowned river valleys, tool-worked timbers, and man-made structures in roughly 300 feet (91 m) of water off the Black Sea coast of modern Turkey. Radiocarbon dating of freshwater mollusc remains indicated an age of about seven thousand years.

Deluge theory

Main article: Black Sea deluge theory

In 1997, William Ryan and Walter Pitman from Columbia University published a theory that a massive flood through the Bosporus occurred in ancient times. They claim that the Black and Caspian Seas were vast freshwater lakes, but then about 5600 BC, the Mediterranean spilled over a rocky sill at the Bosporus, creating the current communication between the Black and Mediterranean Seas. Subsequent work has been done both to support and to discredit this theory, and archaeologists still debate it. This has led some to associate this catastrophe with prehistoric flood myths.

History

Ivan Aivazovsky. Black Sea Fleet in the Bay of Theodosia, just before the Crimean War.

The steppes to the north of the Black Sea have been suggested as the original homeland (Urheimat) of the speakers of the Proto-Indo-European language, (PIE) the progenitor of the Indo-European language family, by some scholars (see Kurgan; others move the heartland further east towards the Caspian Sea, yet others to Anatolia).

The land at the eastern end of the Black Sea, Colchis (now Georgia), marked for the Greeks an edge of the known world.

The Black Sea was a significant naval theatre of World War I and saw both naval and land battles of the World War II.

Regional organizations

Black Sea Economic Cooperation (BSEC)   members   observers	GUAM Organization for Democracy and Economic Development
Community of Democratic Choice (CDC)   members   observers	Black Sea Forum for Partnership and Dialogue (BSF)   members   observers

See also the Balkans Regional organizations and Post-Soviet Regional organizations

See also

The Bulgarian coastline

• Anoxic event
• Black Sea deluge theory
• Bulgarian Black Sea Coast
• Romanian Black Sea Coast
• Ancomah
• Tourism
• 1927 Crimean earthquakes

References and bibliography

• Charles King, The Black Sea: A History, 2004, ISBN 0-19-924161-9
• William Ryan and Walter Pitman, Noah's Flood, 1999, ISBN 0-684-85920-3
• Neal Ascherson, Black Sea (Vintage 1996), ISBN 0-09-959371-8
• Özhan Öztürk. Karadeniz: Ansiklopedik Sözlük (Black Sea: Encyclopedic Dictionary). 2 Cilt (2 Volumes). Heyamola Publishing. Istanbul.2005 ISBN 975-6121-00-9.
• Rüdiger Schmitt, "Considerations on the Name of the Black Sea", in: Hellas und der griechische Osten (Saarbrücken 1996), pp. 219–224
• West, Stephanie. "‘The Most Marvellous of All Seas’: the Greek Encounter with the Euxine", Greece & Rome, Vol. 50, Issue 2 (2003), pp. 151–167.

External links

• Space Monitoring of the Black Sea Coastline and Waters
• Black Sea Environment and Marine Life - Learning Pages
• The Center for Black Sea Archaeology
• The Black Sea Trade Project
• Earth from Space: Black Sea
• National Geographic Society
• Black Sea Environmental Internet Node
• Black Sea-Mediterranean Corridor during the last 30 ky: UNESCO IGCP 521 WG12