NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC lOI 



VII. RELATION BETWEEN THE TEMPERATURE AND THE AIR 



PRESSURE DISTRIBUTION OVER THE NORTH 



ATLANTIC OCEAN 



If one seeks to determine the influence of the winds on the sur- 

 face temperature of the ocean he must examine the condition of 

 the surface layers in the dififerent seasons of the year. In northerly 

 latitudes where the evaporation is less than the precipitation the 

 salt content is increased in winter in consequence of the mixture 

 of the underlying layers by a vertical circulation, while in the sum- 

 mer the salt content diminishes in consequence of the precipitation 

 which being warm would remain on the surface and thereby a 

 lighter layer is formed. Besides this the upper surface water in 

 a large part of the ocean is diluted by the coast water and also 

 by the polar water. These surface layers spread about over much 

 greater areas in summer than in winter, because their specific 

 gravity is considerably smaller partly by the increased dilution 

 and partly by warming. If, however, the evaporation is greater 

 than the precipitation, the yearly march is reversed and the highest 

 salt contents at the ocean surface is found in summer and the low- 

 est in winter. 



ACTION OF WINDS ON SURFACE TEMPERATURES 



How does the action of the winds on the surface temperature 

 adapt itself in dififerent cases? 



As a general rule we must expect that if the wind in the field 

 blows from regions of the sea where the surface is warmer, then 

 the surface temperature in the field in question will tend to rise 

 because warmer waters will be brought by the winds. But if the 

 winds come from a region of colder ocean surface, the reverse 

 will happen. In particular cases, however, there are many devia- 

 tions from this rule. 



If the sea is covered with a thin top surface which is warmer 

 than the water lying below, then a strong wind, by stirring the 

 water in the upper layers may produce a lowering of surface tem- 

 perature even though this wind comes from the warmer regions of 

 the sea. If the ocean has a fresh-water surface, which by reason 

 of its small salt content is lighter than the water lying below, and 

 this layer by the outward radiation in winter becomes colder than 

 the underlying layers, then a strong wind by stirring up the water 

 may cause a rise of the surface temperatures, even if it comes from 

 colder regions of the ocean. 



