56 



surface. In preparing the maps it is necessary to make some approxi- 

 mation, at the stations where the depth of water does not extend 

 down to the reference surface, for the effect of the specific volume of 

 the water below the equipotential surface cutting the bottom. The 

 method used in the 1934 work is known as the Helland-Hansen and 

 Nansen method which Helland-Hansen describes in "The Sognefjord 

 Section", pages 270-272 in the James Johnstone Memorial Volume. 

 It is briefly described by A. J. Clowes, Hydrology of the Bransfield 

 Strait, Discovery Reports, volume IX, pages 39-40, 1934. The 

 method requires the construction of a vertical section of anomaly 

 of specific volume and involves a knowledge of the shape of the 

 bottom profile along the section. To permit the use of this method, 

 therefore, frequent sonic soundings were taken between deep water 

 and the shallow end of each section. As the results are more reason- 

 able than those obtained by the use of the Jacobsen and Jensen 

 method the additional labor involved is considered justifiable. 



To facilitate the determination of the current velocity at any place 

 on a dynamic topographic chart a table was made up and has been 

 in use on the ice patrol vessels for the last 2 years. This table has 

 been expanded and is presented here as table 1. The headings of 

 the table are self-explanatory so that the manner of its use need not 

 be described. 



Referring to the current chart for April, figure 17, it will be seen 

 that the Gulf Stream although present immediately southwest of the 

 tail of the Grand Banks was not in evidence as far south as latitude 

 41°30' N., in longitude 50° W. The Labrador current is probably 

 weaker and farther in on the Banks than is usual. 



In the current map for May, figure 18, it will be noted that the 

 Labrador current sets in on the Grand Banks with a decidedly westerly 

 component in about latitude 46° N. This no doubt grounded many 

 bergs here during the early stages of their southward travel along the 

 eastern edge of the Grand Banks. An inspection of the May ice 

 map, figure 14, between latitudes 46° N. and 47° N., bears this out. 

 A comparison of the April and May current charts shows that the 

 northern edge of the Gulf Stream advanced northward in longitude 

 50° W., from a position somewhere south of latitude 41°30' N. to 

 nearly 42°30' N. The westward intrusion of the Gulf Stream be- 

 tween latitudes 44° N. and 45° N., developed in intensity but had not 

 yet succeeded in closing off the Labrador current. The vigorous- 

 northeasterly current found in the April map just south of the 1,000- 

 fathom curve between latitude 45° N. and 46° N., was very markedly 

 abated. 



