portatioii for bergs westward of the 50th meridian should any reach the 

 Tail of the Banks. Their only chance of further progress would be along 

 the isobath of 971.1 dynamic meters which course would bring them into 

 the shoal water of the banks at about 51° W., where they would probably 

 strand in the vicinity of the slow clockwise whorl shown centered at 

 about 43°10' N., 50°30' W. 



Figure 18 shows the thermal structure of the upper layers along a 

 section run from the southeas-tern edge of the surveyed area to the 

 northern edge, from bathythermograph casts made at intervals of about 

 10 miles as the Evergreen crossed the area returning to port. The water 

 over the banks, with temperatures between about 0.5° and 2.0° C is seen 

 at the left. Remnants of the Labrador Current are shown at the edge 

 of the banks with a minimum of about — 0.5° and at the right is shown 

 the mixed water with temperatures of 6° to 14°. 



The current map resulting from the second survey is shown in figure 

 19. The dynamic topography shows very little of the Labrador Current 

 passing westward of the Tail of the Banks, where it is confined to a band 

 about 10 miles wide between 42°50' N., and 43°00' N. On the banks 

 immediately northward of this is a slow clockwise eddy. At the south- 

 western corner of the charted area and again l^etween longitudes 48° and 

 49° W., from 41° to 42°30' N., is to be seen the northern edge of the 

 Atlantic Current outlining an area of colder mixed water characterized 

 by a series of at least three cyclonic eddies. The axis of the mixed water 

 can be traced from about 41°10' N., 48°44' W., to 42°08' N., 49°21' W., 

 to 43°15' N., 48°26' W. Northward of the area for which the dynamic 

 topography is given, the direction of flow, estimated from the BT sec- 

 tions, is indicated by broken lines. These hues are not intended to in- 

 dicate either current velocities or volume of flow. At latitude 45° N., 

 the southward flowing current is made up of two bands, the major one of 

 which is located outside the 1,000-fathom curve and extends eastward as 

 far as the 48th meridian. The lowest temperatures found were in this 

 band which is presumed to be the Labrador Curi'ent which is normally 

 found inside the 1,000-fathom curve. Between the above-mentioned 

 two bands of southward flowing water is water of higher temperature 

 estimated to be moving in a cyclonic eddy. This slow moving eddy was 

 probably derived from the intrusion of the Atlantic Current water whose 

 salient is directed toward the Grand Banks at about latitude 44° N. If 

 this were its origin it was cut off, prior to the date of the survey, by the 

 Labrador Current flowing southward along the 48th meridian. This 

 latter current forms the tongue of colder mixed water which has been 

 indicated in figure 19 as extending east southeastward as far as 43° N., 

 46° W. Northward of latitude 45° N., the uncertainty of the indicated 

 cui-rent estimates becomes greater but there is evidence of a cold water 

 break-through to the southeastward in the vicinity of about 45°25' N., 

 44°45' N. 



The six BT sections resulting from casts made during the May survey 



74 



