Ocean and Oceanography

In 1902 at Stockholm was founded the International Council for the study of the sea, whose headquarters are in Copenhagen. At present (1928) all the north-east and north-west European States, with the exception of Russia, are represented there. The idea is to help and control the fisheries in the Baltic, the North sea, the Norway sea and Barents sea, as well as in British and Irish waters. Portugal, Spain and Italy have also become mem bers of this union, which has done much to improve the instru ments and. methods of oceanography. Generally, each Govern ment has built or fitted out a research steamer for the work. The United States of America, Canada and Japan also take part.

Extent of the

hydrosphere covers nearly three quarters of the earth's surface as a single and continuous expanse of water surrounding four great insular land-masses known as the continents. Water predominates in the unexplored north polar area, and it is very unlikely that new land of any great extent exists there. On the other hand, recent antarctic exploration makes it certain that a great continent surrounds the south pole with a total area of about 14,000,000 sq.km. Thus there is a total land area of 148,892,000 sq.km., and a total water area of 361,059,000 sq.km., 29% of land and 71% of water, or a ratio of 1:2.43.

Divisions of the

arrangement of the water sur face on the globe is far from uniform, the ocean forming 61% of the total area of the Northern and 81% of that of the Southern Hemisphere. Of the whole ocean only 43% (154.7 million sq.km.) lies in the Northern Hemisphere and 57% (206.4 million sq.km.) in the Southern. A great circle can be drawn upon a globe in such a way as to divide it into two hemispheres, one of which contains the greatest amount of land and the other the greatest amount of sea of any possible hemispheres. The centre of the so-called land hemisphere lies near the mouth of the Loire (471° N. and 21° W.), while the centre of the so-called water hemisphere lies to the south-east of New Zealand and eastward of Antipodes island. Even in the land hemisphere the water area (135.6 million sq.km.) is in excess of the land area (ii9.4 million sq.km.), while in the water hemisphere the amount of land is quite insignificant, 29.6 million sq.km. compared with 225.4 million sq.km. of water. The outline of the water surface depends on the outline of the basins in which it is contained. The four great continental masses, therefore, give the ocean a distinctly tripartite form, the three great divisions being known as the Atlantic, the Indian and the Pacific oceans, all three running together into one around Ant arctica. Thus the connecting belt of water is narrow as compared

with the extent of the oceans from north to south. The propor tions are not readily grasped from a map of the world on Mer cator's projection and must be studied on a globe.

Each of the three meridional oceans has an Antarctic facies in the southern part. Some authors prefer to consider these southern parts as a Great Southern ocean. Only the Atlantic possesses a really Arctic facies north from the narrowest part of Davis strait, north of Denmark strait and north of a line running from Iceland to Jan Mayen and Spitzbergen.

Where the ocean touches the continents the margin is in places deeply indented by peninsulas and islands marking off portions of the water surface which from "all antiquity have been known as "seas." These seas are more or less dependent on the ocean for their regime, being filled with ocean water. These seas may be classified according to their form either as "enclosed" or as "partially enclosed" (or "fringing"). Enclosed seas extend deeply into the land and originate either by the breaking through of the ocean or by the overflowing of a subsiding area. They are con nected with the ocean by narrow straits, the salinity of the water contained in them differs in a marked degree from that of the ocean, and the tidal waves are of small amplitude. Four great intercontinental enclosed seas are included between adjacent continents—the Arctic sea, the Central American or West Indian sea, the Australo-Asiatic or Malay sea and the Mediterranean sea. There are also four smaller continental enclosed seas each with a single channel of communication with the ocean, viz., the Baltic sea and Hudson bay with very low salinity, the Red sea and Persian gulf with very high salinity.

The fringing or partially enclosed seas adjoin the great land masses and are only separated from the oceans by islands or peninsulas. Hence their tidal conditions are quite oceanic, though their salinity is usually rather lower than that of ocean water. The four fringing seas of eastern Asia parallel the main lines of dis location in the neighbouring land masses, as do the Andaman sea and the Gulf of California. On the contrary, the North sea, the British fringing seas, and the Gulf of St. Lawrence cross the main lines of dislocation.