Figures 9 and 10 show the dynamic topography of the sea surface 

 relative to the 1,000-decibar surface found during the second and 

 thhd surveys. The area covered in each of these surveys was the 

 same and has a small area between 47° and 48° N., in which it overlaps 

 that covered by the first survey. While the period covered by the 

 observations of the second cruise (14 days) is somewhat longer than 

 normal for a current survey of the Grand Banks, adjacent sections 

 were as nearly synoptic as is ordinarily the case. The area of overlap 

 shows little change between the first and second surveys. Not only 

 were the surface velocities of the Labrador Current subnormal but m 

 the valley between the Grand Banks and Flemish Gap the Labrador 

 Current was especially weak at depths greater than about 400 mej:ers. 

 The dynamic topography is remarkably flat between 46° and 47° N., 

 from the eastern edge of the Labrador Current eastward to Flemish 

 Cap Had bergs been present to enter the surveyed area via the 

 Labrador Current from the north, the chcumstances were such that 

 if they arrived at the 47th parallel comcident with strong westerly 

 winds they might have crossed this area of weak steady currents to 

 get into positions of hazard near the 46th parallel in and east of the 

 longitude of Flemish Cap. WhUe the Labrador Current was weak it 

 was possible for bergs to reach the Tail of the Banks. From this 

 position there would have been little likelihood of them gettmg farther 

 west than about the 51st meridian, and the locality m which they 

 might have penetrated farthest into the steamer lanes was the rela- 

 tively cold mixed water pool which extended southeastward nearly to 

 41° N.. between 48° and 49° W. i,- u . i 



Comparison of figure 10 with figure 9 shows the changes which took 

 place durmg the 5-week interval between the second and thnd surveys. 

 North of 45°30' N., and west of 47° W., there was Httle change m the 

 pattern and the principal change here was an mcrease of about 20 

 percent in the surface speed. East of 47° W., the area of very qmet 

 water was replaced by a more active movement of mixed water re- 

 turning northward. South of 45°30' N., the most striking feature 

 was the westward mcursion of the salient associated with the Atlantic 

 Current, and the recurving of practically all of the Labrador Current 

 north of the 44th parallel. This left the colder mixed water south- 

 eastward of the Tail of the Banks circulating in a closed eddy, it is 

 to be noted that although the dynamic height of the highest point m 

 the edge of the Atlantic Current, in the southeastern margin of the 

 survey, was very nearly the same and in the same position m the third 

 survey as in the second survey, the difference m height between 41 N., 

 and 42° N., at 50° W., was materially less than that found during the 



'' ConsidTeTas a progressmg meander, the salient of Atlantic Current 

 water showed a northward rate of progression during the interval 

 between the second and third surveys of about the same order of mag- 



39 



