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Oil Spills on the Eastern Mediterranean and Black Seas and the
– Oil Spills
Bosphorus and Dardanelles Straits
HSE
a report by
Tülay Çokacar
Senior Researcher, Chemistry and Environment Institute, Gebze
Turkey is surrounded by seas with a substantial amount of tanker current profiler (ADCP) measurements,
4
the Rim Current jet has a
traffic. The Black Sea together with the Turkish straits system (TSS) speed of 50–100cm/s within the upper layer. In winter, the upper
and the north-eastern Mediterranean, starting from the Gulf of layer is homogenised up to 50m depth, with temperatures of 5–6°C
Iskenderun at the eastern end, are two major routes used to and salinity of 18.5–18.8 parts per thousand (ppt).
8,9
By spring, as
transport the oil produced in Russia, Azerbaijan and Central Asia the temperature in the mixed surface layer increases, stratification
to the west. The catastrophic consequences of oil spills in many begins to develop above a cold water lens, known as the cold
critical regions, such as Istanbul, have been admitted by various intermediate layer (CIL), which is a remnant of the convectively
authorities, leading to comprehensive research in the region. The
region is relatively well-known in terms of its hydrodynamic
characteristics, and there are several ongoing efforts to develop an
With a surface area of
operational near-realtime prediction system for oil spills.
423,000km
2
, the Black Sea is
The Eastern Mediterranean Basin and the Black Sea constitute two
one of the world’s largest inland
largely isolated water bodies constrained by water exchanges through
marine environments.
straits. Both regions are highly sensitive to anthropogenic and climate-
induced variations, as the surrounding land mass is highly developed
in terms of industry and tourism and they are in close proximity to generated cold water mass in winter. The summer mixed layer is
major atmospheric centres of action (e.g. the North Atlantic Ocean, typically less than 20m deep and is characterised by temperatures up
the Sahara and the Indian Ocean). Their oceanographic features are to 25°C and salinity around 1ppt.
7
briefly reviewed below from an oil spill perspective.
The dominant wind direction is north and north-east in the western
Black Sea part of the Black Sea, whereas south-westerlies dominate in the
With a surface area of 423,000km
2
, the Black Sea is one of the eastern part of the basin. Gales from the north-west are common
world’s largest inland marine environments. Its connection to the in winter.
2
The air temperature has a strong north–south gradient in
Mediterranean Sea is through two narrow straits: the Bosphorus and winter, but is more uniform during summer.
2
The air temperature
the Dardanelles. The dissolved oxygen depletes at around 75–150m, decreases sharply in late October and November, reaching a
depending on the region, and the rest of the water column up to minimum of around 0ºC in January and February.
2
2,000m is anoxic. The Black Sea is known as the largest anoxic water
body in the world. The freshwater input from rivers and the Turkish Straits System
atmosphere exceeds the water lost through evaporation; therefore, The Bosphorus and Dardanelles Straits, together with the Marmara
the Black Sea has a positive water balance. The difference is Sea (an area of 11,500km
2
) that lies between them, constitute the
balanced out by the net outflow through the Bosphorus.
1,2
The TSS. The system possesses a two-layer flow structure in which
fluxes through the straits, dramatic changes in topography, dynamic the lower-layer flow is driven by the density differences between the
atmospheric forcing and freshwater input from rivers are the Black Sea and the Aegean Sea, and the upper-layer flow is driven by
principal factors governing the circulation and thermohaline the higher sea-level elevation of the Black Sea with respect to the
structure of the Black Sea. The upper layers of water are Aegean Sea.
10,11
The relatively fresh surface waters originating from
characterised by a predominantly cyclonic, strongly time-dependent the Black Sea (average salinity 18ppt) flow through the Bosphorus
and spatially structured basin-wide circulation.
3–6
Two cyclonic sub- into the Marmara Sea and the Aegean Sea through the Dardanelles
basin scale gyres comprising four or more gyres within the interior of Straits. Saline Mediterranean waters (average salinity 35.5ppt)
the system and a series of anticyclonic gyres in the coastal side of the entering the Marmara Sea through the Dardanelles Straits flow in
Rim Current zone are the characteristic features of the Black Sea the opposite direction in the lower waters through the TSS,
circulation system (see Figure 1).
7
According to acoustic Doppler eventually exiting from the Bosphorus into the Black Sea. The flow
in both straits is hydraulically controlled. In the Bosphorus Straits,
three hydraulic controls exist due to contraction at the middle and
Tülay Çokacar is a Senior Researcher at the Chemistry and Environment Institute in
Gebze, Turkey. Previously, she was a Research Assistant at the Institute of Marine
the sills near either end, which lead to the development of so-called
Sciences, Middle East Technical University (IMS-METU), and obtained her MSc and PhD
maximal exchange flow conditions.
1,10,12–14
The flow regime in the
from the same institution.
Dardanelles Straits differs from that of the Bosphorus in that there is
E:
tolay.cokacar@marm.gov.tr
a single hydraulic control at the mid-strait constriction section, which
implies a submaximal exchange.
10,15
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© TOUCH BRIEFINGS 2009
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