Basic Principles of the General Oceanic Circulation 



571 



The northern part of the North Pacific Current turns northward and flows in an 

 anticlockwise direction around the Gulf of Alaska; it is a well-developed current and 

 is fairly constant, particularly near to the coast. This Alaska Current flows along the 

 Aleutians and extends into the southern Bering Sea through all the passages between 

 the islands. In the eastern part of the Pacific the southward movement off the Cali- 

 fornia coast is denoted the Californian Current (Thorade, 1909; Warmer, 1926). 

 It replaces the water which is carried westward by the north-east trade winds. The 

 north-east to south-west direction of the current indicates the presence of an ofi"- 

 shore movement, giving rise to the upwelling of cold water along the greater part of 

 the Californian coast. This upwelling occurs mainly during the warm part of the year. 



The northward to north-westward movement of water along the entire western 

 coast of South America is called the Humboldt Current after its early investigator. 

 Where it runs close to the Chilean and Peruvian coasts it is called the Peru Current 

 and this current and its variations have been described in a detailed monograph by 

 ScHOTT (1931). A later evaluation of the available data has been given by Gunther 

 (1936, 1936a). Figure 261 shows the probable field of motion according to Schott for the 

 two seasonal extremes. During the period of intensified trade winds in the Southern 

 Hemisphere winter (Chart a, Aug.-Sept.) the Humboldt drift current and its con- 

 tinuation, the South Equatorial Current, intensify considerably. The strength of the 

 current rises from 0-5 to 0-7 knots along the coast of northern Chile and Peru and 

 increases to 1 and occasionally 2 knots where it flows north-westwards in a wide 

 region around the Galapagos Islands. Further out to sea it turns westwards. The 



W-Lq 



W-Lg 



Fig. 261. Most probable current pattern in the region of the Humboldt Current and north 



of it (according to Schott): {a) for the Southern Hemisphere winter (August/September); 



(6) for the Southern Hemisphere summer (February/March). 



