Chapter VII 



THE GllAND BANKS SECTOR 



The Grand Banks sector is defined as the region south and east 

 of Newfoundland which embraces the Labrador Current. The dis- 

 cussion refers particularly to the eastern slope of the Grand Banks 

 along which the Labrador Current carrier icebergs farthest south 

 into the North Atlantic, A frigid branch of the Labrador Current 

 often prevails between the Grand Banks and Cape Race and may 

 extend southwestward to the continental edge. Also cold water 

 from the Labrador Current continually spread in over the bottom 

 of the Grand Banks for considerable distances where the configura- 

 tion favors such incursions. The shallowness of the Grand Banks 

 waters permits no satisfactory dynamic topographic maps, and the 

 primary circulation is indicated mainly by the boundary surfaces 

 of temperature and salinity. Illustrations of the distribution of 

 temperature and salinity over the Grand Banks have not been in- 

 cluded since they have already been published by Smith (1924). 



THE SURFACE CURRENTS 



The system of prevailing circulation of the surface layers in the 

 Grand Banks sector is shown on the composite dynamic topographic 

 map of the surface relative to 1,500 decibars (fig. 126, p. TO). When 

 this chart is compared with the distribution of temperature and 

 salinity, horizontal and vertical (figs. 96 to 99), it indicates that the 

 Labrador Current flows southward along the eastern slope of the 

 Grand Banks, to the vicinity of the Tail, where practically all of it 

 turns eastward, joining the Atlantic Current. In this manner much 

 of the Labrador Current water returns and may even complete a 

 circuit of the Labrador Sea. Throughout the course of the Labrador 

 Current in the Grand Banks sector, branches are turned back along 

 the outer side and as in the American sector it loses water through 

 cabbeling along its offshore side. Although this process contributes 

 some northern water to the upper levels of the North Atlantic (see 

 Iselin, 1936, fig, 57), the major compensating return to the system 

 as a whole is concentrated at deeper levels and in the manner as 

 explained in chapter VIII. 



The inshore margin of the Atlantic Current crossing the fifty- 

 second meridian follows near the 4,000-meter isobath around the 

 Grand Banks to the vicinity of the forty-fourth parallel, where the 

 border of the current bends inshore across the forty-eighth meridian 

 and then recurves south of Flemish Cap. 



Cyclonic eddies are oft«n found along the boundary of the Lab- 

 rador Current and the Atlantic Current, one particularly east of 

 the Tail of the Grand Banks near latitude 42°-30', longitude 49°-00', 

 and the other west of the Tail in the vicinity of longitude 51°-30'. 



129 



