40 



Figure 24 shows the current map resulting from the second survey. 

 Comparison of this map with figure 23 shows a similar current pattern 

 with some of the irregularities smoothed out. The previously found 

 central cyclonic eddy had been absorbed and the pattern of inter- 

 twining tongues which had previously existed at about latitude 45° 

 N., was smoothed out. Possibly connected with the disappearance of 

 this eddy, the border of the Atlantic Current in this northeastern 

 corner of the map was found to have moved westward into the area 

 covered by the survey. The highest dynamic height of the survey, 

 although found about 70 miles farther south, was about 25 dynamic 

 centimeters higher than in the first map. One of the items of much 

 interest from the standpoint of the drift of menacing ice is the west- 

 ward encroachment of a characteristic salient of the Atlantic Current 

 in about latitude 45° N. Under favorable conditions this salient has 

 developed, on occasion, to the point where it reached the edge of the 

 Banks and, forcing the Labrador Current to recurve north of it, 

 formed an effective bar to the southward drift of bergs. It is doubt- 

 ful whether or not the above-described change in the position and 

 strength of this salient between the first and second surveys can be 

 considered as any notable advance toward the Labrador Current. 

 At the surface the northernmost section shows the Labrador Current 

 to have been flowing with very nearly the same strength as that foimd 

 in the first survey. Consequently, the slight growth of the area of 

 the cold mixed water pool in spite of the northward movement of the 

 high dynamic isobaths of the Atlantic Current (such as that of 971.2 

 dynamic meters), seems attributable to the disappearance of the 

 central cyclonic eddy. The westward extension of the cold water 

 pool remained about the same but the southward extension reached 

 the more southerly limit of about 41°20' N. One of the most striking 

 features of the survey was the abnormal development of the Grand 

 Banks whorl extending from latitude 45° N., to the Tail of the Grand 

 Banks. As a result the apparent Labrador Current was much 

 widened and speeded up over this distance. Although this was of 

 no significance with regard to the transportation of ice to the Grand 

 Banks region, it would have been of great importance in the drift to 

 the steamer lanes of any bergs entering the northern part of the area. 

 It would also have been of decisive importance if a fluctuating Gulf 

 Stream system had started a westward encroachment of the Atlantic 

 Current in the 45th parallel salient. 



The dynamic topographic maps resulting from the two halves of 

 the third survey are shown in figures 25 and 26. An inspection of 

 figure 25 shows that between the second survey and the first half of 

 this survey the surface velocity of the Lal)rador Current had decreased. 

 Comparing figures 25 and 26, it will be noted that a further decrease 

 in surface velocity occurred between the two halves of this survey, 



