of the Bonavista triangle. The low velocities along its northwestern 

 side, between stations 7822 and 7825, and the acconijDanying com- 

 plicated low velocity current pattern, produce an apparent separation 

 of the eastern and western branches. From the rest of the chart 

 adjacent to the southeastward, however, it would appear that the 

 eastern and western branches are divided by the isohypse of 971.04 

 dynamic meters. At the southern margin of the chart the minimum 

 dynamic height marking the eastern boundary of the Labrador 

 Current shifted eastward progressively during the four surveys; 10 

 miles between the fii'st and second, 3% miles between the second and 

 third, and 17 miles between the third and fourth for a total shift of 

 some 30 miles from April to June. Although less precisely defined, 

 the eastern boundary of the Labrador Current at the northern edge 

 of the surveyed area shifted westward about 25 miles between the 

 second and fourth surveys. As in the second survey; the dynamic 

 topography in the northeastern half of the area showed little relief 

 during the fourth survey. 



In the Grand Banks region there are two water masses, Labrador 

 Current water and Atlantic Current water, which mix with proportions 

 usually sufficiently constant to produce a virtual water mass, the 

 mixed water. Based upon the observations made during the first 

 and third sm'veys, the temperature-salinity relationships found in 

 1961 have been shown in figure 19 as solid lines. For comparison, 

 the T-S curves representing the means for the 14-year period 1948-61 

 have been shown as broken lines. 



Except for the upper 300 meters in the Atlantic Current, the tem- 

 peratures were higher than nonnal in 1961 in each water mass. In 

 the Labrador Current water at levels of 100 meters and above, the 

 higher temperatures were accompained by lower salinities to produce 

 lower densities. At 150 and 200 meters, an increase in salinity offset 

 the eft'ect of higher temperatures to maintain normal densities. At 

 the 300- and 400-meter levels, higher salinities produced greater than 

 normal densities. In the mixed water, salinities compensated tem- 

 peratures to ap])roxinuile normal densities down to about 100 meters. 

 Below that level, densities were lighter than normal. In the Atlantic 

 Current water, the densities were less than normal at levels deeper 

 than 200 meters. 



Over the years, several s 'ctions across the Labrador Current have 

 l)een occupied repeatedly. Many of these have a sufficient munber 

 of occupations to permit the estimation of tentative normal seasonal 

 variation relationships. The sections are defined as follows: South 

 Wolf Island, extending 045° T from South Wolf Island, Labrador 

 aiormals published in Bulletin No. 44 of tliis series); sections XW, 

 SW and SE, forming the northwestern, southwestern and southeastern 

 sides of the Bonavista triangle (normals published in Bulletin Xo. 

 39 of this series); section H, parallel to and about 40 miles south- 



27 



