204 MAlJIOISr EXPEDITION TO DAVIS STRAIT AXD BAFFIKT BAY 



type of circiilatioii. (Smith 1924a, p. 133.) A similar type of cir- 

 culation has been observed bv Mathews (1914, }). SS) ; bv Hunts- 

 man (19l!4, p. 280); and by 'Bioelow (192T, p. 921); it is also in 

 fact a characteristic feature of practically all of the coastal waters 

 along those parts of the northeastern American shelf that are boreal 

 in character but ice free at the time. We must conclude from the 

 above that the oceanic system of currents, at least in the higher lati- 

 tudes of the northern seas, characterized by offshore expansion in 

 the surface layers and a salty indraft beneath is set in motion not l)y 

 the ice but by the belts of water around the sides of the basin, oceano- 

 graphically known as '" coastal." 



Perhaps it is because the ice catches the eye and the imagination 

 ]nore than do the coastal water masses with which it is ordinarilv 



The Cold Wall off the American Coast 



FiGUEB 122. — A remarkable photograph taken March 27, 1922. south of Newfound- 

 land, in latitude 41° 40' N., longitude 51° 07' W., looking westward along the 

 meeting zone of the Gulf Stream and the Labrador current. The surface water 

 on the cold side 'of the wall (to the right) with a temperature of 34° F. was 

 smooth and glassy. The warm water (to the left) with a temperature of 56° F., 

 choppy and rippled. There was a range of 22° F., therefore, in less than a ship's 

 length. This important oceanographic l)ouudary marks a critical point in the 

 disintegration of the icebergs that drift out of Davis Strait into the western 

 North Atlantic. (Official photograph, international ice patrol.) 



associated that its relative importance in the picture of oceano- 

 graphic circulation has been overemphasized."^ The regional dif- 

 ference of density between coastal and oceanic waters is the main 

 springs for the convectional currents. The winds, also, by their 

 direct frictional effect, combined with the presence of coast lines 

 or other hindrances, develop significant slope currents. In any case, 

 however, we can not refer the impelling forces to a riverlike source; 

 in fact, they work along the entire extent of floAv. 



The transition zones, i. e., the continental slopes, the continental 

 edges, and the ridges, mark the belt of greatest energy, and in the 



»3 Pettersson (1927. p. 7) has even stated that the force that deflects the Gulf Stream 

 towards the north and west, against the effect of earth rotation, is to be explained as an 

 effect of northern ice. 



