decreased salinities at all levels produced a deciease in density at all 

 levels. 



In the area just to the north of the Grand Banks the Labrador 

 Current divides into a usually minor western branch which flows 

 southward along the Avalon Peninsula and an eastern branch which 

 is that part of the Labrador Current which follows the eastern slope 

 of the Grand Banks. As opportunity permits, data are being- col- 

 lected which will teach us more about the behavior of the Labrador 

 Current in the vicinity of this branch point. Three sections disposed 

 to form the sides of a triangle which includes the branch point form 

 the basis for such study as it has so far received. The triangle is 

 defined by its corners which are located at Cape Bona vista, 49°23'N., 

 50°00' W.; and 50°00' N., 49°00' W. Eariier surveys of the tri- 

 angle were made once in 1948 and twice in 1949. In 1950 it was 

 occupied once during the period 27-30 May and partially in the 

 period 13-15 July when the northern and southwestern sections 

 were occupied, and on 28-30 July when the southeastern and northern 

 sections were occupied. 



One of the questions which have been considered was whether the 

 surface current pattern in the vicinity of the triangle is sufRciently 

 representative of the currents in the upper 150 or 200 meters to per- 

 mit the movement of a deep draft berg to be deduced from the dy- 

 namic topography of the surface. The measurements which have so 

 far been made show a good similarit}" of pattern in these levels. 

 Figures 23 and 24 show respectively the dynamic topography at the 

 sea surface and at the 100-decibar surface relative to the 1000- 

 decibar surface. 



A second question of practical importance, and one which will 

 require more study, deals with the rapidity with which the current 

 pattern in this vicinity may change. Probably some change took 

 place between the beginning and end of the survey on which figures 

 23 and 24 are based. The dynamic heights of all of the stations 

 except those in the northeastern part of the triangle are referred to 

 deep water by integration of the product of depth and anomaly of 

 specific volume along bottom beneath the sections. In this case the 

 dynamic heights of the shallow water stations may be arrived at by 

 two approaches. LTsing these two approaches the dynamic heights 

 do not agree and the triangle fails to close by about 52 dynamic 

 millimeters when the vertical sections of anomaly of specific volume 

 are reasonably constructed. One is faced by the choice of introduc- 

 ing extreme gradients of anomaly of specific volume which are not 

 supported by the observed temperatures and salinities, or the assump- 

 tion that changes took place during the survey. The latter has been 

 chosen as the more probable. 



Assuming that changes took place during the survey there is a 

 further question as to whether the change was gradual enough to 



79 



