The Three-dimensional Temperature Distribution and its Variation in Time 1 1 3 



same. A comparison of the oceanic and continental annual temperature variations is 

 given in Table 45. 



Table 45. Annual temperature variations (°C) 



* Only Northern Hemisphere 



Figure 50 shows isopleths for the annual surface temperature variations in the At- 

 lantic. It can be seen at once, that there is a narrow zone just north of the equator, 

 where there is a six-monthly temperature variation so that over the whole of the tropics 

 the amplitude of the annual temperature variation remains very small and that the 

 middle latitudes between 30° and 50° show a maximum which decreases towards the 

 pole, especially in the Southern Hemisphere. 



The annual temperature variation is transmitted to the deeper layers beneath the 

 surface by the effect of convection and turbulence, with a corresponding reduction in 

 amplitude and a retardation of the extremes, until it finally disappears. However, 

 the annual displacements of water masses can also simulate an annual temperature 

 variation, which is then not due to the total production and expenditure rates of heat 

 at that point, but to others at more distant parts of the sea. Our present knowledge 

 of these phenomena is still very poor. To obtain the exact annual temperature varia- 

 tion at deeper layers it is necessary, because of the small number of observations 



Jan. Feb. Mor. April Moy June July Aug Sept. Oct. Nov. Dec. Joa 



Fig. 50. Isopleths of surface temperature in the Atlantic Ocean. 



