NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 9 1 



we should expect a progressive march of the variations from place 

 to place accompanying the transportation of the ocean water- masses. 



Variations in the temperature of the oeean surface and the air 

 may also be brought about by variations in the strength or direction 

 of the zinnds. This may work in different ways : In part by the 

 winds transporting warmer or cooler air-masses and tending to 

 warm particular regions of the ocean surface or to cool them. They 

 may act also to produce waves upon the ocean by means of which 

 the upper ocean layers are disturbed and the deeper lying water is 

 brought up to the surface, and thereby the surface is generally made 

 colder. Finally the winds may act by lateral displacement of the 

 surface layers, whereby a field of observation may receive warmer 

 or colder layers of water brought in from elsewhere. 



It may also be thought that variations in the temperature of the 

 ocean surface and of the atmosphere may be attributed to the varia- 

 ations in the intensity of the solar radiation at the earth's surface. 

 Such variations could for example be brought about by greater or 

 less cloudiness. Cloudiness acts in general in summer to diminish the 

 temperature and in winter to increase it on account of its influence 

 on the solar radiation and the outgoing radiation of the earth. But 

 a cause of variation in the solar radiation may occur higher in the 

 atmosphere and depend upon varying quantities of volcanic dust 

 thrown high up by great volcanic eruptions and remaining suspended 

 in the higher layers of the air for long periods of time. 



The temperature variations could be brought about also by varia- 

 tions in the outgoing radiation of the earth on account of absorption 

 conditions changed by the influence of carbon dioxide, ozone, or 

 other vapors. 



But tlie temperature variations may also have cosmic causes 

 depending for example on periodic or non-periodic variations in the 

 radiation of the sun, outside the atmosphere. Such solar changes 

 might produce directly variations in the temperatures measured in 

 the ocean or in the air near the earth's surface or they may act in- 

 directly by calling forth changes in the atmosphere of the earth, such 

 for example as alterations in the thermal relations of the higher air 

 layers or in the atmospheric electric potential or in the terrestrial 

 magnetism or in the earth currents. These changes in the atmos- 

 phere could again act in different ways to produce changes in the 

 distribution of air pressure, the formation of clouds and the distri- 

 bution of temperature on the earth's surface. 



