Oceanic Circulation and Temperature 



An examination of other coastal regions indi- 

 cates the presence of a similar type of circulation 

 ojff the west coasts of South America and Africa. 



Aeration of Ocean Water Due to Overturn- 

 ing. — As recently pointed out by Juday, some agent 

 other than diffusion is responsible for the aeration 

 of large bodies of water. In lakes the aeration is 

 accomplished by the spring and summer overturn- 

 ing and the resulting circulation which continues 

 for some time afterward. The type of circulation 

 just described for the Pacific amounts to a con- 

 tinual overturning of the water. There are good 

 reasons for believing that the bottom water in the 

 North Pacific is derived largely from the Antarctic 

 Ocean, and that the return of the surface water to 

 the Antarctic is accomplished in part by a slow 

 southward surface drift due to diff'erences in den- 

 sity of the upper layers of water, and in part by 

 the motion of the upper air which carries moisture 

 to the poles where it is precipitated. Thus it fol- 

 lows that aerated water is continually carried down 

 to the depths of the ocean, especially in the south 

 polar region, and is forced upward in upwelling 

 coastal regions. It is manifest that the downward 

 current would supply oxygen to all depths, and 

 the upward current by transporting nitrogen and 

 carbon dioxide from tne sea bottom would enrich 

 the upper layers, especially of the coastal water, 

 thus giving rise to an increased production of 

 plants. Numerous observations on the general fer- 

 tility of coastal areas where upwelling is indicated 

 by other evidence corroborate this conclusion. 



Determination of Oceanic Circulation from 

 Biological Facts. — Dr. A. H. Clark recently formu- 

 lated a hypothesis of oceanic circulation to account 

 for the distribution of the Crinoids, one of the 

 widely distributed bottom animals. While he infer- 

 red that the cold in-shore water was of Antarctic 

 origin, his hypothesis of the character of the circu- 

 lation is quite contrary to the conclusions just re- 

 viewed, which were based on hydrographic evi- 

 dence. 



Though biological evidence may be of value in 

 supplementing and checking our knowledge of the 

 broader aspects of oceanic circulation, it is evident 

 that the most reliable results must be obtained from 

 direct observations on the water itself. 



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