topography is referred to the 2,000-decibar surface although use 

 of the deeper reference surface gives higher velocities. 



The southern edge of the eastward flowing current was found 

 at about 38°30'N. A reversal of direction was observed between 

 40° N. and 40°30'N. This appears to be associated with a 

 meander to the northwestward and is identified with the current 

 pattern found between 42° N. and 42°30'N. between 51° W. 

 and 52 W. It is interesting to note that the highest dynamic 

 height found in the Atlantic Current in the eastern part of the 

 surveyed area (station 6778 in the vicinity of 43°15'N., 

 45°30'W.) is found in the middle of the swiftest band of current 

 between stations 6744 and 6745 on the southern section. Com- 

 pared with the first survey, the Labrador Current lost the high 

 velocities found earlier near the Tail of the Banks but its tem- 

 perature minimum remained decidedly warmer than normal, the 

 coldest temperature observed being —1.00°, found in the north- 

 ernmost section. 



The dynamic topography shown in figure 22 is that found during 

 the postseason cruise occupation of the Bonavista triangle. Com- 

 pared with the similar area of figure 20, there was a northward 

 and seaward shift of the current pattern. There is usually a sea- 

 sonal decrease in the proportion of the Labrador Current following 

 the eastern branch. This decrease was somewhat greater than 

 normal in 1958. It dropped from 90 percent during the second 

 survey (compared with a seasonal normal of 88.3 percent) to 

 82 1/ 2 percent at the time of the postseason cruise (compared with 

 a seasonal normal of 8414 percent). The minimum observed tem- 

 peratures along the three sides of the triangle were close to normal 

 during the postseason cruise although the coldest temperature 

 occured along the northwestern side instead of the southwestern 

 side where it usually is found. 



The first and third surveys took place in the region of the 

 Grand Banks from which sufficient data are available to permit a 

 comparison of the temperature-salinity characteristics of the 

 water masses found there in 1958 with the mean T-S characteristics 

 for earlier years. Labrador Current water and Atlantic Current 

 water are water masses found in this region and these parent water 

 masses usually mix in a sufficiently constant proportion to produce 

 a mixed water which may be regarded as a virtual water mass. 

 Figure 24 shows the relationships found in 1958 as solid line 

 curves. The broken lines represent the 11-year means for the 

 period 1948-58. 



Of the three the mixed water is least definite and some stations 

 are found where the mixing is atypical and data from these sta- 

 tions are excluded in determining the T-S relationship of the 



40 



