swept westward to ground on the Grand Banks northward of about 

 44° N. could have been expected to reach track C at about 49° "VV. 

 Another area indicated by ligure 15 as one of potential ice hazard 

 to traffic folloAving U. S. -European tracks was that southeastward 

 of 42°30' N., 47°00' W. In the southwestern part of the area sur- 

 veyed, the margins of the Gulf Stream system were present with 

 dynamic heights greater than 971.1 dynamic meters. This dynamic 

 isobath also approximated the boundary of the Atlantic Current 

 water in the strong salient extending westward toward the banks 

 betAveen latitudes 43° N. and 45° N. With the current pattern found 

 in this survey, the possibility of a break-through of Labrador Current 

 water and bergs immediately southward of Flemish Cap was limited 

 to latitudes north of 45°30' N. 



Figure IG shows the dj^namic topography found during the third 

 cruise. A striking feature of this survey is the complicated current 

 pattern in the area between about 44° X. and 45° N. and 48° "\V., and 

 50° W. A slow counterclockwise eddy has been shown centered near 

 44° N., 49° W., for simplicity, although the actual djaiamic topog- 

 raphy may have been better represented by a valley associated with 

 the Labrador Current and extending southwesterly toward 44° X., 

 49° W., and bordered on its southern side by a promontory associated 

 with the Grand Banks eddy and jutting easterly beyond the 1,000- 

 fathom curve. Such an interpretation would be in accord with the 

 clockwise circulation of the Grand Banks eddy, which is often in- 

 tensified seasonally and centered around the shoalest part of the 

 Grand Banks. In either case the axis of the Labrador Current is dis- 

 placed seaward from its usual position and is well outside the 1,000- 

 fathom curve at the 44th parallel. Northward of this latitude the 

 Labrador Current maintained its previous strength and continued to 

 supply the area of cold mixed water southeastward of the Tail of 

 the Banks. 



Large diameter clockwise eddies or salients which characterize the 

 outer margins of the Atlantic Current in this region have been ob- 

 served to progress along the boundaries of that current in the direc- 

 tion of its flow. "With the time interval between surveys of the order 

 of magnitude of 1 month and with the diameters of the eddies rang- 

 ing between about 50 and 150 miles, the only cases in which suc- 

 cessive surveys have permitted the identification of such progressing 

 eddies or salients have been those in which the rate of progress has 

 l)een slow. A comparison of figures 15 and 1(5 shows the possibility 

 of interpreting the current patterns found during the second and 

 third cruises as a case in which salients have progressed northeast- 

 ward, with the salient which was centered at about the 44th parallel 

 in figure 15 having moved to the vicinity of 45°30' N., 45°00' W., in 

 figure 16, and the tongue shown in figure 15 near 42° N., 48° W., 



60 



