49 



It would seem that the fluctuations in the boundary of the Atlantic 

 Current are dependent on two sets of causes which if related are only 

 partly and distantly so. These are, namely, fluctuations in the 

 Labrador Current entering the area from the north, moving south 

 along the edge of the Grand Banks, recurving northeastward, and 

 leavmg the area at the north along the boimdary; and fluctuations in 

 the position of the boimdary arising from causes affecting the Gulf 

 Stream system. Now the vohmie of flow of the Labrador Current 

 entermg the area has regularly been determined for each survey at the 

 section which has been called section U. (See table L) To adjust 

 the area, defined as above, for the eft'ect of fluctuations in the Labrador 

 Current 10,000 square kilometers of area have been subtracted for 

 each million cubic meters per second volume of flow of the Labrador 

 Current past section U. Before acceptmg this arbitrary equivalent 

 the following estimates and assimiptions were considered. If the 

 area is assumed to be a square, one-half of which is occupied by the 

 south-bound Labrador Current and the other half of which is the 



northward return, the width of the current or its return is ^^' As- 

 suming the depth of the current to be 1,000 meters and assigning 1 

 million cubic meters per second as requiring 10,000 square kilometers 

 of area, the volume of flow being equal to the width times the depth 

 times the average velocity, S, we can wi'ite: 



10«=xl2!! X 10^ S (meters per second) 



whence /S'=0.02, or 2 centimeters per second, which is of the right 

 order of magnitude. 



Table 2 gives the actual area in units of 10,000 square kilometers, 

 followed by the adjusted area in similar units where adjustment has 

 been made for the volume of flow of the Labrador Current as described 

 above. All surveys made during the 7-year period and covering the 

 region in question are given in chronological order. 



