OCEANIC CIRCULATION 131 



an extensive area of the Indian and Pacific 

 Oceans with a density less than 1023. In 

 temperate regions the density increases, until 

 beyond the fortieth parallels north and south 

 the density usually exceeds 1-026, with well 

 marked maxima in the great Southern Ocean 

 and in the North Atlantic and Norwegian Sea, 

 where densities exceeding 1-027 prevail over 

 large areas, extending in the south as far as 



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Flo. 7. — Diagram showing the general circulation of the waters of the 

 Atlantic Ocean (continuous arrows indicate relatively warm water 

 and dotted arrows relatively cold water). 



lat. 58° S., and in the north as far as lat. 78° N. 

 in the neighbourhood of Spitzbergen. It is 

 especially in these areas of high density that 

 the relatively warm saline waters from inter- 

 tropical regions on being cooled sink down 

 beneath the surface, returning equatorwards 

 to a large extent as a slowly-creeping deep- 

 seated undercurrent, and being drawn pole- 

 wards to a less extent to replace the water 

 carried away by the polar surface currents, 

 as shown in the accompanying section, which 

 is constructed diagrammatically to illustrate 

 the general system of circulation in the Atlantic 

 (see Fig. 7). It may also be pointed out 

 that the waters which leave the surface in 



