CANADIAN FISHERIES EXPEDITION, 19U-15 291 



The layer of cold water is thinner in the centre of the gulf of St. Lawrence 

 than at peripheral parts of the same; the layer is thus in cyclonic circulation. 



The extent and permanence of the cold water layer show that no interchange of 



Fig. 60. — Circulation of the water in a transverse section 

 of a current with cold bottom water. 



water can take place between the surface and bottom layers in the gulf of St. 

 Lawrence. The cold layer forms an elastic but impenetrable membrane between the 

 surface water and the bottom water. Its level is dependent upon the state of the 

 Labrador current, and thus probably determined by the seasons; also accidental causes 

 may, however, have some effect. With an easterly wind, when great quantities of sur- 

 face water will be pressed in and corresponding masses of bottom water forced out 

 through Cabot strait, the level of the cold layer will sink in the gulf, and rise outside 

 it. With a westerly wind, on the other hand, when the surface water is driven out 

 and the bottom water sucked in through Cabot strait, then the level of the cold layer 

 is raised inside the gulf and lowered outside. Enormous slow wave movements also 

 probably take place within the layer. x\s its level approximately corresponds with 

 that of the Banks, its change of level will obviously occasion marked changes of 

 temperature there. These changes of temperature, moreover, probably affect the 

 occurrence of fish on the banks, as the fish may be presumed to seek that water they 

 best like. In seeking to locate the fish, therefore, it will undoubtedly be valuable to 

 know at what level this cold water is to be found. 



The warm bottom layer in the gulf of St. Lawrence is connected with the outer 

 world only by the long, deep channel of the Cabot strait. No production or consump- 

 tion of this water takes place in the gulf of St. Lawrence, and its movements there 

 are consequently insignificant. In the deep channel through the Cabot strait, how- 

 ever, this water may at times exhibit no inconsiderable degree of movement. Measure- 

 ments of this deep-water current would be of great dynamic importance, possibly 

 also important in biological respects, since they would show whether the cold layer 

 were rising or falling, i.e., in what direction the hydrographic condition of the gulf of 

 St. Lawrence is tending. The deep water of the gulf of St. Lawrence may be considered 

 as an elastic membrane exhibiting a number of important hydrographical phenomena, 

 all of which exert their influence upon it. The current flowing inward and outward 

 through the deep channel of Cabot strait indicates the measure of this influence, and 

 thus affords a valuable means of discerning what is taking place in the gulf of St. 

 Lawrence. 



