416 CLARK: ABYSSAL TEMPERATURES 



(1) Temperatures all above the average (South and Central 



America to the Gulf of California) 



(2) Temperatures all below the average (southern California 



and northward to and including the Bering Sea) 



(a) Temperatures considerably below normal (south- 



ern California and the Gulf of Alaska) 



(b) Temperatures slightly below normal (central 



California to Alaska) 



(c) Temperatures intermediate (Bering Sea) 



The regularity in the rise in the temperature of the abyssal 

 water from Chile to the Panamic region and the subsequent 

 drop in temperature along the Mexican coast suggests that the 

 temperature of the deep water in the vicinity of the coast is 

 influenced by the volume of warm water delivered in the region 

 of Panama and southern Central America by the Equatorial 

 Counter Current which, unable to extend to the northward 

 because of the strong California Current which acts as a barrier, 

 is exerted to the southward along the South American coast, 

 within the region dominated by the Humbolt Current. 



There is no need in this connection for assuming any ex- 

 tensive flow of water southward along the South American coast, 

 for a relatively slight amount of water delivered in the upper 

 layers on the northwestern South American coast would suffice 

 to depress the isotherms sufficiently to give the figures observed. 



The Gulf of Alaska is essentially a backwater or cul-de-sac, 

 and the marked coldness of its abysses appears to indicate that 

 this condition extends to its greatest depths ; that is to say, that 

 the coldness of its abysses is due to local causes, chiefly the chill- 

 ing of its upper layers in winter. It is probably this chilled water 

 from the Gulf of Alaska moving southward which causes the 

 deficiency in the temperature of the deeper levels (as well as 

 of the upper layers), all the way to the region just north of the 

 Gulf of California. x 



It would appear that the water off southern California in the 

 well known region of up-welling is colder than in the region 

 between southern California and the Gulf of Alaska. There 

 is no reason why this should be so unless the cold water along 



