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sea,term used as synonymous with oceanocean,
interconnected mass of saltwater covering 70.78% of the surface of the earth, often called the world ocean. It is subdivided into four (or five) major units that are separated from each other in most cases by the continental masses. See also oceanography.
..... Click the link for more information. , or a subdivision of an ocean (Caribbean Sea, Yellow Sea), or erroneously designating a large salt lakelake,
inland body of standing water occupying a hollow in the earth's surface. The study of lakes and other freshwater basins is known as limnology. Lakes are of particular importance since they act as catchment basins for close to 40% of the landscape, supply drinking water,
..... Click the link for more information. (Caspian Sea, Dead Sea, Aral Sea).
a part of the world’s oceans that is more or less set apart by land or elevations of the submarine terrain and primarily distinguished from the open ocean by hydrological, meteorological, and climatic conditions. The distinguishing characteristics of a sea result from its position on the margin of the ocean, which means that land has a significant influence on it, and from the limited connection with the open ocean, which is reflected primarily in slower water exchange. Thus, the more a sea is enclosed by land, the more it differs from the ocean. Some open parts of the ocean are arbitrarily called seas—for example, the Sargasso Sea in the northern Atlantic and the Philippine Sea in the western Pacific. Some lakes are called seas (for example, the Aral Sea and Dead Sea), and some seas are called gulfs or bays (Hudson Bay, the Gulf of Mexico, and the Persian Gulf). The diversity of characteristics associated with seas makes their classification very difficult. The most complex classifications belong to German scientists (Krummel  and others); the most complete are the classifications of the Soviet oceanographers lu. M. Shokal’skii (1917), N. N. Zubov and A. V. Everling (1940), and A. M. Muromtsev (1951).
Seas are divided into three groups on the basis of their degree of isolation and their hydrological conditions: internal seas (inland and semienclosed seas), marginal seas, and interisland seas. Inland seas are sometimes divided according to geographical position into intercontinental and intracontinental seas. (See Table 1 for data on some major seas.)
From a geological point of view, the modern seas are young formations. All of them had been established in nearly their present-day outlines in Paleocene-Neocene times and took final shape in the Anthropogenic period. The deepest seas formed at the points of major faults in the earth’s crust (for example, the Mediterranean Sea). Shallow seas appeared when the waters of the ocean flooded the marginal parts of the continents as they subsided or the level of the ocean was uplifted; they are usually located on the continental shelf.
The climates of seas are distinguished by features of greater or lesser continentality, depending on the degree to which they are isolated by land. This is primarily reflected in the magnification of seasonal fluctuations in air and surface water temperature. Some seas are warmer than neighboring open parts of the ocean on the surface and at greater depths (for example, the Red Sea), whereas others are colder (the Sea of Okhotsk); this depends on geographic position. Seas have all the extreme values of salinity of the world’s oceans; in the open part of the Baltic Sea, salinity is only 6.0-8.0 parts per thousand (‰ whereas in the Red Sea it reaches 41.5×‰. Water density in the seas also reaches extreme values, in conformity with the distribution of extreme values of temperature and salinity (density of 1.0100 g/cm3 in the Baltic Sea and 1.0287 g/cm3 in the Red Sea).
Cyclonic currents predominate in seas because of the prevalence of the cyclonic system of winds above the seas and the continental discharge, which is deflected in the corresponding direction by the force of the earth’s rotation.
The organic world of the seas differs from that of the open ocean in a larger percentage of forms not found in other regions (endemics) and often also in a relatively greater variety. Both phenomena are based on the isolation of the sea basins and the differences in conditions in comparatively limited spaces. An additional factor is differences in the geological history of the basins.
REFERENCESShokal’skii, lu. M. Okeanografiia, 2nd ed. Leninigrad, 1959.
Muromtsev, A. M. “Opyt raionirovaniia Mirovogo okeana.” Trudy Cos. okeanograficheskogo in-ta, 1951, no. 10.
Leonov, A. K. Regional’naia okeanografiia, part 1. Leningrad, 1960. More [collection]. Moscow, 1960. (Translated from French.)
A. M. MUROMTSEV
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