200 WATER MASSES AND CURRENTS OF THE OCEANS 



crosses long. 170°W, because at a number of the Bushnell stations the 

 temperature-sahnity curves are similar to those of the Kuroshio water. 

 The greater part of this water appears to turn around toward the south 

 before reaching 150°W, and only a small portion continues and flows south 

 between the Hawaiian Islands and the west coast of North America after 

 having been mixed with waters of different origin. The main part of the 

 North Pacific Current does not therefore extend across the Pacific Ocean, 

 but turns back toward the west in the longitude of the Hawaiian Islands. 



The Aleutian (Subarctic) Current. To the north of the North 

 Pacific Current one finds a marked transition to an entirely different 

 type of water, the Subarctic Water, which alsp flows toward the east. 

 Between the Aleutian Islands and lat. 42°N the transport above the 

 2000-decibar surface of Subarctic Water amounts to about 15 million 

 m^/sec. This water mass must have been formed by mixing of Kuroshio 

 and Oyashio water, the temperature of the mixture having been reduced 

 by cooling and the salinity of the upper layer having been decreased by 

 excessive precipitation. One branch of the Aleutian Current turns 

 north and enters the Bering Sea, following along the northern side of 

 the Aleutian Islands and circling the Bering Sea counterclockwise. 

 In the Bering Sea, these waters are further cooled, and, flowing south, they 

 reach the northern islands of Japan as the cold Oyashio. The amount of 

 water in this gyral is not known, but since inflow and outflow from the 

 Bering Sea must be nearly equal, it follows that the 15 million m^/sec of 

 Subarctic Water that continue east on the southern side of the Aleutian 

 Islands are supplied by the Kuroshio, the waters of which have been 

 completely transformed by mixing and external influences. 



Before reaching the American coast the Aleutian Current divides, 

 sending one branch toward the north into the Gulf of Alaska and another 

 branch toward the south along the west coast of the United States. The 

 former branch is part of the counterclockwise gyral in the Gulf of Alaska. 

 It enters the Gulf along the American west coast, and, since it comes 

 from the south, it has the character of a warm current in spite of the fact 

 that it carries Subarctic Water. It therefore exercises an influence on 

 climatic conditions similar, on a small scale, to that which the North 

 Atlantic and the Norwegian Currents exercise on the climate of north- 

 western Europe. The major branch, which turns toward the south along 

 the west coast of the United States, is known as the California Current, 

 but before dealing with this it is desirable to discuss the warm-water 

 currents between the Hawaiian Islands and the American West Coast. 



The Eastern Gyral in the North Pacific Ocean. The existence 

 of an eastern gyral is recognized mainly by the character of the water 

 masses and by the results of computations based on observations between 

 the Hawaiian Islands and the coast of California and between the 

 Hawaiian Islands and the Aleutian Islands. The study of water masses 



