Table III 



Volume transport through standard section A3 in x 10**m.^/sec. 



Date of 

 Occupation 



22 & 23 April 

 24 May 

 30 May 



* (<2.0°C., <34.3%„) 



Southward 



Transport West 



of Trough 



2.19 

 4.54 

 7.44 



Cold Core* 

 Southward 

 Transport 



1.29 

 2.34 

 2.89 



% Southward 



Transport Due 



Cold Core 



59% 



52% 

 39% 



Cold Core* 

 Northward 

 Transport 



0.00 

 0.01 

 0.40 



Cold Core* 

 Net Transport 



1.29 

 2.33 

 2.49 



1963 by Smith et al. (1966). Thus, in addition 

 to producing wind driven currents, the prevail- 

 ing winds altered the mass distribution through 

 downwelling and intensified the Labrador Cur- 

 rent. 



The circumstances surrounding an intensifica- 

 tion of the Labrador Current observed during 

 9-19 June 1964 (fig. 20) were investigated to 

 determine if downwelling was involved then 

 also. Observations were made at section U 

 (nearly the same as standard section A3) on 

 13-14 June 1964 (fig. 21). Examination of the 

 six-hourly, surface, hemispheric weather charts 

 revealed that during the 96-hour period pre- 

 ceding the observations the mean wind direction 

 was 013° true, and the mean wind speed 18.8 

 knots. Again, water in the surface layer was 

 transported toward the continental slope result- 

 ing in an accumulation of relatively cold, fresh 

 water near the shelf break (fig. 21). The distri- 

 bution of mass on 13-14 June 1964 (fig. 22) was 

 very similar to that of 29 May 1970 (fig. 19). 

 Thus the 1964 case appears to be a second ex- 

 ample of wind induced mass transport towards 

 the continental slope producing downwelling and 

 intensification of the Labrador Current. 



The changes in volume transport with time at 

 standard section A3 (fig. 23 and table III) were 

 about the same as previously observed in 1966 

 (Wolford, 1966), 1968 (Andersen and Moyni- 

 han, 1971), and 1969 (Moynihan and Andersen, 

 1971) but were significantly less than those ob- 

 served in 1967 (Morgan, 1969). Again note that 

 the changes in the southward transport of the 

 cold core of the Labrador Current were consid- 

 erably less than the changes in the southward 

 transport west of the trough. 



Results 



No valid conclusions can be drawn from the 



comparisons of transport values with other 

 years since the observations were randomly and 

 irregularly spaced in time ; there could be many 

 maxima and minima in volume transport that 

 were not observed. On both standard sections 

 A2 and A3 the fluctuations in the southward 

 transport of the cold core coincided with much 

 larger fluctuations of the total southward trans- 

 port (figs. 16 and 23). The changes in the total 

 transport were more than twice those of the 

 cold core. The volume transport through stan- 

 dard section A3 (fig. 23) is more variable than 

 that through standard section A2 (fig. 16) . Both 

 the these phenomena also were observed in 1967 

 and 1968 (Morgan, 1969 ; Andersen and Moyni- 

 han, 1971). This implies that changes in the 

 volume transport of the Labrador Current may 

 be caused by atmospheric or oceanic conditions 

 on the eastern slope of the Grand Banks rather 

 than farther north along the Newfoundland or 

 Labrador coasts. The presence of colder and 

 fresher water from the north may be necessary 

 for the Labrador Current to accelerate but in- 

 creases in the "supply" of such water may not 

 necessarily be the mechanism which causes the 

 accelerations. Other possible causes could be 

 wind driven accelerations, "set up" on the conti- 

 nental shelf due to storms, downwelling along 

 the continental slope, and interaction of the 

 North Atlantic and Labrador Currents. Concur- 

 rent time series observations at standard sec- 

 tions A2 and A3 may provide further evidence 

 to support this thesis. 



DIRECT CURRENT MEASUREMENTS 



Direct current measurements were made at 

 two anchor stations during the first cruise (fig. 

 2) and with two taut-line instrumented arrays 

 during the post season cruise (fig. 4) . 



