NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 49 



Dr. Engeler's work entitled " Periodic and Non-Periodic Temper- 

 ature Variations of the Benguela Current" (1910) may be men- 

 tioned here since it is concerned with the variations of the surface 

 temperatures of the eastern part of the South Atlantic Ocean, simi- 

 lar to those which we have hitherto discussed in the North Atlantic 

 Ocean. His investigations extend over the years 1891 to 1898 and 

 are based upon observations along the German sailing ship route, 

 round the south end of Africa, as well as those of the English steamer 

 route between Cape Colony and Europe. He finds great variations 

 of the surface temperatures from year to year, with well marked 

 maximum and minimum periods, and these come for the most part 

 about the same time in the whole investigated region. He thinks 

 that these variations cannot be attributed to non-periodic incursions 

 of cold water-masses from the Antarctic Ocean since the effect of 

 these must be gradually spread northward between the southern and 

 northern part of the investigated ocean current and could not affect 

 both of its branches simultaneously. 



On the other hand he thinks that strong ice drift with quantities 

 of icebergs in the South Atlantic Ocean may have produced in single 

 periods as in the years 1893 and 1894 a certain influence on the 

 variations, and have tended to limit the maximum periods and in- 

 tensify the minima. It is little remarkable that he does not note 

 that this action which he must also attribute to the extension of cold 

 water northwards must have made itself most felt in the southerly 

 part of the current rather than in the northern exactly as if it 

 depended upon intrusion of cold water-masses from the Antarctic 

 ice ocean, unless he assumes an intervention of the air temperature. 



Engeler attributes as the principal cause of the variations of the 

 surface temperature of the Benguela Current " the non-periodic 

 variations of the intensity of the southeast trade winds with which 

 they are associated in an unbroken chain of cause and effect." By 

 an increase or diminishing of the strength of the trades, the trans- 

 portation of currents of cold water is increased or diminished and 

 the surface temperature correspondingly sinks or rises. 



He thinks that another influence of winds of non-periodically 

 varying intensity may lie in the fact, that in consequence of the 

 greater circulation of the waters an uprise of cold water from the 

 bottom must take place in the current, since the greater velocities 

 must hinder the approach of water-masses from the south. " Such 

 a moment occurs naturally at all points of the current simultane- 

 ously. Which of these two processes has the principal influence 



