物理海洋学名词-A 10

Glossary of Physical Oceanography and Related Disciplines

Steven K. Baum Department of Oceanography Texas A&M University

May 26, 2004

 

Aegean Sea A marginal sea in the eastern Mediterranean Sea centered at approximately 25◦E and 38◦N. It is located between the Greek coast to the west, the Turkish coast to the east, and the islands of Crete and Rhodes to the south. It contains more than 2000 islands forming small basins and narrow passages with very irregular coastline and topography. The northern part of the Aegean is also known as the Thracian Sea, and the southern part between the Cretan Arc and the Kiklades Plateau (defined as the 400 m isobath) as the Cretan Sea. It contains an extended plateau (Thermaikos, Samothraki, Limnos and Kyklades) as well as the deep basins the North Aegean Trough (1600 m maximum depth), the Chios Basin (1160 m) and the Cretan Sea (two depressions in the east 2561 m and 2295 m deep). It covers an area of 20,105 km2, has a volume of 74,000 km3, and a maximum depth of 2500 m.
It is connected to the Levantine Sea to the southeast via the Cassos or Kasos Strait (67 km wide, 1000 m deep) between Crete and Karpathos, the Karpathos strait (43 km wide, 850 m deep) between Karpathos and Rhodes, and the Rodos or Rhodos Strait (17 km wide, 350 m deep) between Rhodes and Turkey. It joins the Ionian Sea and Cretan Sea to the southwest through the Antikithira Strait between Crete and Antikithira (32 km wide, 700 m deep), the Kithira Strait between Antikithira and Kithira (33 km wide, 160 m deep), and the Elafonissos Strait between Kithira and Peloponnese (11 km wide and 180 m deep). There is considerable and complicated interchange of water with the eastern Mediterranean through these passages. The Strait of Dardanelles (55 m deep, 0.45–7.4 km wide) provides a northern link to the Black Sea from which the Aegean receives around 190 km3 per year of water.
The climate in the Aegean Sea area is characterized by the presence of two distinct periods, summer and winter, with spring and autumn relatively short and transitional. The topography and continual alternation of land and sea make the climate highly variable. Annual river runoff averages about 18,800×10^6 m3, and evaporation exceeds precipitation and river runoff. The most prominent wind pattern is the Etesian winds, which are persistent, northerly, cold and dry winds that often reach gale force in July
and August. When this wind approaches the southern Aegean is bifurcates, becoming northeasterly over the Kitherian Straits and northwesterly–westerly over the southeastern Aegean. The Etesians vanish in late autumn to be replaced by violent cyclonic storms and highly variable prevailing winds.
The surface circulation is most affected by the summer Etesian winds and the low salinity inflow from the Black Sea. The winds cause upwelling along the western coasts of the islands in the eastern Aegean, and a accompanying cold surface zone with temperatures 2–3◦C lower than in the northern and western Aegean. During the summer, this colder water is present in the eastern Aegean from Rodos Island up to the Limnos Plateau. In winter, the warmer waters of Levantine origin are found in the same area, while the cold waters arriving from the Strait of Dardanelles spread over the Samothraki Plateau and follow the general cyclonic circulation of the north Aegean. In addition to the overall cyclonic circulation, there is also a Samothraki anticyclonic gyre located in the northeastern part of the North Aegean, a semi-permanent feature that can be detected through most of the year, and an anticyclone
near Athos.
The surface flow in the south is into the Aegean between Kithira and Crete, Crete and Karpathos, Karpathos and Rhodes, and Rhodes and Turkey, and into the Mediterranean between Kithira and the Peloponnese coast. There is systematic wind–driven upwelling along the northern coasts of the Patraikos and Korinthiakos Gulfs.
The main water masses found in the Aegean are (from shallowest to deepest):
• Black Sea Water (BSW);
• Levantine Intermediate Water (LIW);
• modified Atlantic Water (AW); and
• Eastern Mediterranean Deep Water (EMDW).

The BSW enters from the Strait of Dardanelles, producing a pronounced halocline in the norther Aegean with a maximum depth from 20–80 m. It moves southward and westward, following the general cyclonic circulation, and can be detected by a surface salinity minimum as far south as the Kithira Straits. LIW is the saltiest water mass of the eastern Mediterranean. It is generated in the Levantine and southern Aegean Seas in February and March. It flows eastwards and westwards from the Aegean, and also flows into the Aegean via the eastern straits of the Cretan Arc. It predominates in the subsurface layers of the Cretan Sea as well as in the eastern parts of the Aegean as far north as the southern boundary of the Limnos Plateau, and is easily identified by its salinity maximum. The modified AW enters the Aegean through the straits of the Cretan Arc and is identifed in several regions as a subsurface (30–200 m) salinity maximum. The Aegean deep water mass extends from about 400–500 m to the bottom, with temperatures ranging from 12–14.5◦C and salinities from 38.68–38.9. See POEM Group [1992], Stergiou et al. [1997] and Balopoulos et al. [1999].

 

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