formed by the junction of the Baffin Land Current and a branch of the 

 West Greenland Current that crosses to the American side south of 

 Davis Strait ridge. As the Baffin Land Current component contributes 

 the cold, fresh, inshore portion of the Labrador Current, any stagnation 

 or decreased circulation in Baffin Bay probably would result in reducing 

 the extent and intensity of the core of minimum temperature in the 

 Labrador Current, x^s such a result has been noted, most markedly dur- 

 ing 1940 and 1941, possible cause (4) is probable. From the foregoing 

 inventory of the meager available evidence, it would appear that the 

 change in T — S characteristics of the Labrador Current in the Grand 

 Banks region at levels of about 50 to 200 meters is probably the result 

 of a change in the heat balance in the Labrador Sea and Baffin Bay, 

 and a decreased activity of the circulation in Baffin Bay. 



The long-range trend in T — S characteristics discussed above is 

 accompanied by a shift in density. Values of at corresponding to the 

 yearly average temperatures and salinities plotted in figure 12 are 

 shown in figure 13. From this figure it will be seen that the trend in at 

 is toward increasing density at the levels where the T-S trend is toward 

 warmer and saltier water. However, in the deeper levels (400 meters to 

 1,000 meters), the density trend is toward smaller values of at. A 

 long-range trend affecting different areas to different degrees will 

 produce different average conditions of circulation because of the 

 altered horizontal gradients of density. Changes in the vertical density 

 gradient will alter the extent of cabbeling along the boundaries of the 

 current and this in turn will alter the characteristics of the water in the 

 deeper levels. Changes in both horizontal and vertical gradients will 

 change the shape and depth of isentropic surfaces with resultant changes 

 in circulation along these surfaces. LTntil we know more of the mech- 

 anics of circulation and the manner in which the various elements are 

 interrelated, the full significance of such long range trends must remain 

 obscured, and we can only say that the effects of such changes will be 

 far reaching. 



In Bulletin 30 of this series a criterion for the outer boundary of the 

 Atlantic Current was taken as the condition where a temperature of 

 6° C. corresponds to a salinity of 34.95°/oo. The boundary thus defined 

 has been located for each of the 1941 surveys and, as was previously 

 done for the earlier surveys, the area enclosed by the current boundary 

 on the southeast, the 45th parallel on the north, the 49th meridian be- 

 tween latitudes 45° and 43° on the west, and a rhumb line extending 

 from 43° N., 49° W., through 42° N., 47° W., to the current boundary 

 on the southwest, has been determined. A decrease in the area so 

 bounded corresponds to a transverse movement of the boundary 

 towards the Grand Banks and an increase in area corresponds to a 

 retreat of the boundary away from the Grand Banks. As described in 

 Bulletin 30, an adjustment for fluctuations in the strength of the 

 Labrador Current has been attempted by assuming that 10,000 square 



15 



