20 



TEMPERATURE OF THE SURFACE WATERS OF THE ATLANTIC OCEAN 



and iinder; in the north they are apparently somewhat 

 higher. The higher temperature is, however, probably 

 connected with the small width of the front, its unstable 

 position, and the other previously mentioned factors, 

 i. e. Gulf Stream and distribution of water and land. 



Within the polar fronts, between which the tropo- 

 spheric events take place, the subtropical boundary 

 B and B' tends toward the equator. Between 

 A' and B' and A and B lies an area which, 

 compared with the polar zone, has higher temperatures 

 and which is dominated in the south principally by 

 the west wind drift. In any case, the chart of the water 

 movement of the surface of the Atlantic Ocean by 

 Meyer '" shows predominantly purely eastward current 

 directions, especially in these latitudes of the South 

 Atlantic Ocean, while north and south of them, north- 

 easterly directions prevail. In the North Atlantic, the 



»• Footnote 24. 



conditions are more involved. Within this temperate 

 zone of the west wind drift, in the area of the Falkland 

 Current and south of Africa, as well as in the North 

 Atlantic Ocean, fragments of a secondary boundary 

 A/ and A' were found. This fact is explained, as 

 was partly the subtropical boundary itself, by the 

 appearance of a convergence-divergence line in the 

 current system of the west wind drift. The tropical 

 zone of the ocean was defined by the average northern 

 and southern extreme positions of the thermal equator 

 of the water surface. From this fact, it may be deduced 

 that the boundary in the western part of the ocean 

 reaches about 7.5° S. to 10° S. lat. 



Between the equatorial area and the temperature 

 zone of the west wind drift are found the subtropical 

 areas in which lie the great d3'namic convergence areas, 

 already partly recognized by Merz and drawn by Meyer 

 and Felber on their charts. 



