from normal of the difference in sea level across the Bermuda- 

 Charleston section focuses attention on that normal. No extended 

 uninterrupted series of tide gauge records exist for the Bermuda 

 end of the section and so it is not yet possible to draw any conclu- 

 sions regarding changes in mean sea level at that end of the sec- 

 tion. At the Charleston end of the section tide gauge records 

 have continued with reference to the same bench mark since the 

 fall of 1921. They show an increase in sea level with an abrupt 

 rise of about 0.14 foot between 1932 and 1933 to a mean value of 



5.07 for the 8-year period 1933-40 (used in studying the relation- 

 ship with the 27 surveys made 1934-41) with a further increase 

 to a mean of 5.40 for the 4-year period 1947-50 (used in connec- 

 tion with the 8 recent surveys made during 1948-51). It is not 

 known whether sea level at both ends of the section rose or whether 

 the change occurred only at the Charleston end. Nor is it known 

 what part of the change at Charleston represents a sinking of the 

 coast. This is believed to be of a smaller order of magnitude. It 

 is also considered that the rate of change of total volume of water 

 in the oceans is negligibly small. If the sinking of the coast can 

 be neglected and if most of the changes in sea level across the 

 section take place at the outer edge of the North Atlantic eddy, the 

 change can be interpreted as indicating a weaker circulation of the 

 Gulf Stream system during the post-war period. Examination of 

 the tide gauge records, therefore, indicate that the figure of 5.07 

 may continue to be used as the normal sea level from which de- 

 partures may be considered. 



In the Grand Banks sector of the North Atlantic eddy the outer 

 margin of North Atlantic Current water, as defined by the unad- 

 justed area, was somewhat nearer the center of the eddy but main- 

 tained a position which averaged nearly the same for the post-war 

 period as for the earlier period (7.1 X 10^ as compared with 



6.8 X 10^ square kilometers). During the post-war period the 

 volume of flow of the Labrador Current past section U has been 

 decidedly subnormal compared with the earlier period (about 3.0 

 as compared with about 6.8 X 10^' cu.m/sec.) . Qualitatively, then, 

 these changes are in agreement, with the position of the boundary 

 in the Grand Banks sector undergoing little change since both the 

 Labrador Current and the North Atlantic eddy were weaker than 

 previously. 



If a contraction of the boundary of the North Atlantic eddy 

 follows weakening of the circulation in the eddy, the peripheral 

 branches fed by the eddy might be expected to be profoundly 

 affected by such a contraction, especially if the branching is con- 

 ditioned by the configuration of the land or bottom. The Irminger 

 Current, recurving to the westward in the vicinity of Iceland, con- 

 tributes Atlantic water to make the West Greenland Current a 



45 



