202 WATER MASSES AND CURRENTS OF THE OCEANS 



ture extend in a southerly direction away from the coast, and that these 

 tongues are separated from each other by tongues of higher temperature 

 extending in toward the coast. Within the tongues of higher temperature 

 the flow is directed to the north, whereas within the tongues of low 

 temperature the flow is directed to the south. Thus, a series of swirls 

 appear on the coastal side of the current similar to those that Gunther has 

 demonstrated within the Peru Current. 



Fig. 54. Surface temperatures along the coast of California in March to June 

 and in November to January. In regions of intense upwelling the average surface 

 temperature is lower in March to June than in December to January. 



To the north of latitude 30°N the two most conspicuous centers of 

 upwelling are located in latitudes 35°N and 41°N. The two swirls 

 associated with these centers of upwelling and the alternating movements 

 away from and toward the coast are shown in fig. 55, which is based on 

 observations in May to July, 1939. The coast to the south of 34° N is 

 under the influence of water that returns after having traveled a long 

 distance as surface water, and, correspondingly, the surface temperatures 

 are much higher there than those encountered where the water was 

 recently drawn to the surface (fig. 54). A third region of intense upwell- 

 ing is found perhaps in about latitude 24°N, on the coast of Lower 

 California. 



The upwelling water rises from only moderate depths, probably less 

 than 200 m, and the phenomenon therefore represents only an over- 

 turning of the upper layers such as is the case in other regions that have 



