Comparison of the Second and Third Intensive 

 Surveys 



In the final survey we find a further deepening 

 of the dynamic trough. Vohiine transport 

 changes around the survey perimeter were char- 

 acterized by net increases in the easterly direction 

 for the N-S oriented sections "B" and "D'', and 

 increases in southerly transport for E-W sections 

 "A" and "C". The major contributions to tliese 

 net transport differences came from an offsetting 

 increase in Warm Water and a decrease in Cold 

 Core southerly transport which allowed the de- 

 crease in both AVarm Water and Cold Core 

 northerly transport to effect a greater net south- 

 erly transport through the topmost section. This 

 increase was not the result of any rise in the 

 velocity nor the extent of the Labrador Current 

 (figs. 7 and 8). In fact, the surface layer veloci- 

 ties indicate that the current had reached steady 

 state, or perhaps even decelerated, down from a 

 maximum of 55.1 cm S"^ on the second survey to 

 49.1 cm S"^ on the third survey. Rather, a de- 

 crease in the noitherly flow of Cold Core and 

 Warm Water from the second to third survey 

 was the cause of the net southerly increase. This 

 53.2% reduction in northerly flow through the 

 top section coincided with a 28.7% decrease in 

 northward transport through the bottom section 

 and an 18.0% increase in the volume of water 



exiting the survey area through the eastern sec- 

 tion. The western boundary of the third survey 

 may be characterized as having the least devia- 

 tion of the Labrador Current from the normally 

 bathy metrically defined path along the continental 

 slope. This may be seen from the percentage of 

 Cold Core water passing through the top section 

 of the survey that also passed through the bottom 

 section. This value reached its highest during 

 survey III (71.4%), least during the second sur- 

 vey (26.0%) when there was a large up slope 

 transport of Cold Core water volumes, and inter- 

 mediate (58.9%) during survey I. 



The southern boundary of these surveys showed 

 a variation in northerly transport of Warm 

 Water which may be compared with the dynamic 

 changes in the rest of the survey domain. The 

 northward flow of Warm Water increased 10.6% 

 from the first to second survey and decreased 

 41.0% from the second to the third survey to a 

 level 34.8% below that of the first survey. It is 

 noteworthy that the increased northward trans- 

 port occurred when the south-flowing Labrador 

 Current had a considerable on-slope component 

 of flow and that the lowest northerly transport 

 of Warm Water was correlated with the greatest 

 infiltration of the southern flow of Cold Core 

 water through the survey area. 



13 



