WATER MASSES AND CURRENTS OF THE OCEANS 201 



(fig. 40, p. 158) showed that a distinctly different water mass was present 

 in the region to the east of the Hawaiian Islands, and that this mass was, 

 in part, formed at the boundary between the warmer waters and the 

 Subarctic Water between long. 130° and 150°W. Computation of cur- 

 rents and transport, the results of which are shown schematically in fig. 

 56, p. 205, leads to the conclusion that a clockwise-rotating gyral is present 

 in the eastern North Pacific with its center to the northeast of the 

 Hawaiian Islands. It is probable that the location of this gj^ral changes 

 with the seasons and shifts from year to year, so that occasionally the 

 gyral may lie entirely to the northeast of the Hawaiian Islands, whereas 

 in other circumstances the Hawaiian Islands may lie inside the gyral. 

 If the gyi'al is displaced considerably to the north, Equatorial Water may 

 reach as far north as to the Hawaiian Islands, as was observed in 1939 at 

 one of the Bushnell stations. At the surface the gyral is masked by wind- 

 driven currents. 



The California Current. The California Current represents, as 

 already explained, the continuation of the Aleutian Current of the North 

 Pacific. The name is applied to the southward flow between lat. 48° and 

 23°N, where the Subarctic Water converges with the Equatorial (fig. 40, 

 p. 158). The outer limit of the California Current is represented by the 

 boundary region between the Subarctic Water and the Eastern North 

 Pacific Water, and lies in lat. 32°N at a distance of approximately 700 km 

 from the coast, according to the observations by the Carnegie in 1929, the 

 Louisville in 1936, and the Bushnell in 1939. The total volume transport 

 of the California Current above the 1500-decibar surface is probably not 

 more than about 10 million m^/sec, and, in view of the great width of the 

 current, no high velocities are encountered except within local eddies. 

 As a whole, the current represents a wide body of water that moves 

 sluggishl}^ toward the southeast. 



In spring and early summer the California Current is a counterpart 

 to the Peru Current, several characteristic features of the two currents 

 being strikingly similar. During these months north-northwest winds 

 prevail off the coast of California, giving rise to upwelling that begins 

 mostly in March and continues more or less uninterruptedly until July. 

 Records of surface temperatures show that on the coast the lowest tem- 

 peratures regularly occur in certain localities that are separated by regions 

 with higher surface temperatures. This is demonstrated by fig. 54, in 

 which are plotted the surface temperatures between latitude 32°N and 

 45°N along the American west coast in March to June and in November, 

 December, and January. In the regions of intense upwelling the spring 

 temperatures are lower than the winter temperatures, but in regions of 

 less intense upwelling they are higher. 



Recent work of the Scripps Institution of Oceanography demonstrates 

 that from the areas of intense upwelling tongues of water of low tempera- 



