TEMPERATURE OF THE SURFACE WATERS OF THE ATLANTIC OCEAN 



19 



Figure 20. — Thermoisopleths at the surface for the one-degree field bands 20° W. to 21° W. between 20° N. 

 ard 10° S., with the position of the thermal equator. 



7 the points of intersection of the average northern and real polar zone of the ice-covered sea, but also subpolar 

 southern extreme positions are those of the annual water masses to about 5° C. By their sinking at the 



average, along with the meridians. 



Table 7. — Mosl northerly, average, and 7nosl southerly position of 

 the thermal equator 



front they give the impulse for great interhemisphcric 

 circulation in the lower strata of the Atlantic Ocean. 

 In the south, the temperatures at the front are 5° C. 



Longitude- 



Average northern extreme 



position Latitude. 



Annual average 



Average southern extreme 

 position Latitude- 



90° W. 



60° 



24 N. 



15 N. 

 13 N. 



30° 



12 N. 



5 N. 



7S. 



0° 



3 N. 

 2 N. 



To summarize, it can thus be established that on the 

 basis of temperature distribution and water move- 

 ments, natural areas which correspond approximately 

 to the main climatic zones can be delineated. Thus 

 the polar front (A' Southern Hemisphere, A„.8 Northern 

 Hemisphere) at the surface separates the oceanic 

 stratosphere from the troposphere. Between these 

 fronts and the poles is the domain of the cold water 

 masses that is the polar area of the ocean, which, 

 according to Defant and Wiist, includes not only the 



Figure 21. — Water movement at the surface in the 

 equatorial area in April between 06° W. and 

 37° W., and between 2° N. and 12° S., according 

 to the Dutch current displacements for two- 

 degree fields. 



