234 INTERACTION BETWEEN THE ATMOSPHERE AND THE OCEANS 



that the Atlantic Arctic Front also is located in a region of great energy 

 supply. 



By comparing fig. 64 with figs. 56 and 42, which show the transport 

 of water by currents in the Pacific and the Atlantic, it is seen that the 

 regions of maximum energy supply to the atmosphere are found where 

 water is transported from lower to higher latitudes. Thus, in winter 

 a close relationship exists between the direction of the ocean currents and 

 the location of the atmospheric fronts. The fact that the frontal zones 

 appear to be located where energy is supplied to the atmosphere suggests 

 that in winter the formation of disturbances along the Polar Front and the 

 Arctic Fronts cannot he explained without considering thermodynamic 

 processes. 



Figs. 64 and 65 show only the average amounts of energy supplied 

 from the sea surface, but when deaUng with questions in synoptic meteor- 

 ology the amount of energy supplied to an individual air mass must be 

 examined, and this amount depends upon the past history of that air 

 mass. Thus, polar air flowing out over the ocean will in winter be 

 heated intensely and will receive a large supply of water vapor, whereas 

 tropical air flowing north will be cooled and may lose water vapor by 

 condensation on the sea surface. The importance of these processes 

 toward changing the character of the air masses is fully recognized in the 

 meteorological literature, but data have been lacking for quantitative 

 studies of these changes and their consequences. 



Still another aspect should be mentioned. When discussing the ocean 

 currents it was stated that the energy for maintaining the oceanic 

 circulation is primarily derived from the stress that the prevailing winds 

 exert on the sea surface. It is shown here that the localization of the 

 energy given off from the sea surface is closely related to the oceanic 

 circulation, but this localization, in turn, exercises a considerable control 

 over the prevailing winds. This means that the interaction is complete. 

 Every change in the circulation of the atmosphere must lead to a change 

 of the ocean currents, which, again, must affect the atmosphere. This 

 fact has also been fully recognized by meteorologists, and many attempts 

 have been made to establish the sequence of events in this complicated 

 series. Emphasis has been placed on finding certain time lags that may 

 have a forecasting value. It is reasoned that the heat content of the 

 ocean waters is very great compared to that of the atmosphere, and that 

 therefore any change in ocean currents will for a long time influence the 

 air temperature and the circulation. In some instances a close corre- 

 lation has been found between variations in ocean temperature and 

 subsequent variations in air temperature, such as those along the west 

 coast of Norway, where, according to Helland-Hansen and Nansen, high 

 winter temperatures are experienced if, in the preceding summer, the 

 heat content of the Atlantic water off the coast was high, and vice versa. 



