data prevents a detailed description of this eddy, 

 however, its presence is apparent. 



GENERAL CIRCULATION 



Volume and Heat Flow 



A summary of volume flow through the desig- 

 nated section U is given in table lA. The compu- 

 tations were made by a modified method described 

 by Jakhelln (1936). It is interesting to note 

 that the volume flow through section U doubled 

 during the 9-day interval between the section 

 occupation on the first survey and the check 

 survey. The volume flow then remained relative- 

 ly constant between the check survey and the 

 third survey. It appears that a radical change 

 took place on the Banks between the first and 

 check surveys. Not only is 'a greater volume 

 observed on the check survey but a significantly 

 warmer mean temperature and higher minimum 

 temperature is also found. The third survey 

 volume flow remains high; however, the mean 

 temperature, minimum temperature, and mini- 

 mimi salinity drop below the first survey values 

 indicating that the Labrador Current is exhibiting 

 its full flow characteristics. 



The general water characteristics of the Labra- 

 dor Current between the first and third surveys 

 are quite different. Figure 7A shows a T-S plot 

 of the Labrador Current. The points are mean 

 values (for the given depths) of all stations on 

 each of the first and third surveys situated in the 

 southward flowing stream. This is similar to 

 figure 6A showing the Labrador Current character- 

 istics for the entire season. On the first survey, 

 the water was less stratified than during the third 

 survey. This is indicated in figure 6A by the 

 smaller sigma-t change across the same depth 

 interval on the first survey tlum on the third, 

 particularly from 100 to 150 meters. A com- 

 parison of the water mass between the two surveys 

 shows the third survey found colder, less saline 

 water down to a level between 100 and 150 meters 

 and then a sharp density increase with warmer, 

 more saline water below 150 meters. This 

 density gradient defines the deptli limits of change 

 of the Labrador flow. This change at depth of 

 the density structure between surveys can be 

 traced to spring changes in the east-west slope of 

 the (7, surfaces resulting in greater stratification, 

 and will be treated more fully in the following 

 chapter on isen tropic analysis. 



Dynamic Height Changes 



A surface dynamic height plot of tlie stations 

 of section U on the first, check, and third sur- 

 veys, figure 8A, shows that in 9 days a change in 

 height of the inboard station occurred without a 

 significant change in the trough dynamic height. 

 Tlie trough is located in water which is a mixture 

 of the Labrador Current and the Atlantic Current 

 and does not show the extreme characteristics of 

 either current system. Apparently the abrupt 

 change in elevation of the stations on the Banks 

 and the mcrease in volume flow is related to the 

 change of water characteristics on the Grand 

 Banks and continental slope as shown on the 

 temperature-salmity sections, figure 9A. These 

 sections were constructed from the temperatures 

 and salinities of stations in section U on the first, 

 check, and third surveys. 



The temperature and salmity distributions of 

 section U durmg the three occupations are clearly 

 shown in figure 9A. The first survey reveals that 

 the cold water is generally confined to the surface 

 along with reduced salmity required for stability, 

 probably reflecting the results of disintegrating 

 sea ice. The check survey shows colder water of 

 low salinity to be subsurface and connected to a 

 colder water mass on the Banks. The density of 

 this water is less than the first survey water at 

 the same depth indicating that it probably did 

 not result from surface sinking. By the third 

 survey the situation had again changed showing 

 a core of cold water off the Banks, with even 

 lower salinity than cold water of the previous 

 survey. The salinity decreases as the Banks are 

 approached indicatmg that different water mass 

 has also arrived there. The temperature of the 

 Banks water has also increased above what it was 

 earlier, but this can be explained by the warmer 

 air temperatures as summer approaches. 



Because of the method ol computing currents 

 in the shallo\\' Banks water, the deeper \\ater areas 

 to the east along the slope and below the core of 

 the Labrador Current greatly influence the dy- 

 namic height on the Banks. This is the water 

 located between stations 9252 and 9258 ; 9303 and 

 9304 ; 9390 and 9389 ; on the first, check, and third 

 surveys, respectively, of figure 9A. Between these 

 stations the water shows a definite salinity re- 

 duction with time. First, an increase in the 

 amount of water of less than 34.07oo was observed 

 during the check survey. This is followed by an 

 increase in the amount of water of less than 



