82 



The currents resulting from the dynamic topography just described 

 are shown on Figure 42. The outstanding feature of the circulation 

 is the sinuous form of the outer current, swirling inshore quite markedly 

 at two points along the slope — first on the southwest side of the Bank 

 and later again on the eastern side near the forty-fourth parallel. 

 The ice patrol has never before been able to secure such a satisfactory 

 picture of the currents north of the Tail, as shown on Figure 42. 

 Scanty records have led us to suspect, however, that the outer current 

 often tends to pinch off the Labrador current and the supply of bergs, 

 between the forty-fourth and forty-fifth parallels, more than at any 

 other point along the slope north of the Tail. This locality is often 

 the key to the ice situation. 



After contemplating Figure 42, it is natural to inquire what causes 

 the current to sweep inshore so much closer near the forty-fourth 

 parallel than at other places around the Grand Bank? Let us 

 approach the question by regarding the circulation over a wider 

 area. The cause of flow of the Gulf Stream, for instance, has been 

 the subject of great discussion among scientists, and one popular 

 theory ascribes the motive power to propulsion imparted in the 

 Caribbean. It can be proven, however, that if the water masses 

 forced northward out of the Florida Straits depended solely upon 

 their inertia of motion, the flow would entirely dissipate a quarter 

 of the way to Hatteras. 



The movement of the water particles along the eastern continental 

 edge of North America is, we believe, on the other hand, chiefly a 

 hydrostatic phenomenon caused by the mixing of coastal and oceanic 

 water, forming thereby a heavy water zone. The sequence of events 

 is as follows: First there must be two water masses of different 

 salinity and temperature brought into contact. Under natural con- 

 ditions the saltier mass freshens and the fresher mass salts. The 

 warmer mass cools and the cooler mass warms, all with the important 

 result that such a process creates heavier water than that which 

 originally prevailed. This fact can be proven by taking equal 

 samples, standard for each type of water, coastal and oceanic, around 

 the Grand Banks as follows: 



The density of the resulting mixture, 26.86, it is seen, is greater 

 than that representative for either Gulf Stream or Labrador current. 



