distributed downstream between the mixed water and the Atlantic 

 Current water. 



The position of the cold wall is an important factor in determining 

 the southern limits of berg-infested waters in the vicinity of the Grand 

 Banks. Its fluctuations have been studied and reported on in earlier 

 bulletins of this series. As it is not necessarily a vertical boundary, 

 the boundary selected for study is the horizontal projection of the line 

 along which a temperature of 6° corresponds to a salinity of 34.95%o. 

 The position of this boundary has been described numerically by the 

 area between it and fixed rhumb lines northwestward of it (the 45th 

 parallel, the 49th meridian from 45° N., to 43° N., and a line from 

 43° N., 49° W., through 42° N., 47° W.). Thus, as the boundary 

 moves toward the Grand Banks, the area decreases. It was con- 

 sidered that the position taken up by the boundary was determined 

 partly by forces associated with the North Atlantic eddy and partly 

 by forces associated with the Labrador Current. An assumption was 

 made that the area would be increased by 10,000 square kilometers 

 for each million cubic meters per second volume transport of the 

 I^abrador Current entering the area past section U. After subtracting 

 ^uch an amount from the area to obtain an adjusted area. A, this 

 adjusted area was considered as representing the effects of causes 

 associated with the Gulf Stream system. A further assumption was 

 made that these causes w^ere related to the difference in sea level be- 

 tween Bermuda and Charleston, S. C, and hence that fluctuations in 

 A would be related to fluctuations in this sea-level difference. With 

 sea level at Charleston minus the departure from average sea level at 

 Bermuda, in feet, designated as H, and A in units of 10,000 square 

 kilometers with a time lag of 13}2 months, 27 survej^s made during the 

 ice patrol seasons 1934-41 gave the expression 



A=6.8 (//-5.07) + 1.34. 



Following the interruption of World War II, surveys were resumed 

 in 1948. The postwar surveys have not agreed with the above relation- 

 ship but followed a similar relationship if 1 1 K months was used as the 

 time lag instead of 13K months. Ten surveys made during the period 

 1948-52 were combined with the 27 prewar surveys, using 11^ months 

 for the postwar time lag, to derive the expression 



^=6.97 (i?-5.07)4-1.67. 



Two further surveys made in 1953 did not fit either of the above ex- 

 pressions, and examination of the fluctuations in sea level indicated 

 that the tune lag might have been either UK or 13K months. Three 

 surveys made in 1954 indicated the IIK month time lag was still 

 applicable and the actual values of A were —0.03, 1.31, and 3.35 



97 



