at cold tempernturps comparable to the water 

 temperature in the area of the mooring site 

 (<4°C). 



D)ie to the current meter failure, the other 

 (lata obtained in connection with tiie moorin<r 

 are not presented. The mooring line tension and 

 inclination, and current meter deptli. as recorded 

 by tiie additional instrumentation, were com- 

 patible with the computer prediction for antici- 

 pated current speeds. 



DYNAMIC TOPOGRAPHY 



The circulation regime in tlie Grand Banks 

 area is usually cliaracterized by a cold, narrow 

 Labrador Current flowing southward along the 

 steep continental slope and by a warm broad 

 North Atlantic Current flowing northeastward 

 further off shore to the east. The corresponding 

 dynamic topography (fig. 3) derived from 

 monthly mean values (Scobie, 1976) is char- 

 acterized by closely spaced contours indicating 

 the two currents and widely spaced contours 

 fonuing a broad dynamic trough between them. 



The dynamic topography for the first IIP sur- 

 vey (8 to 20 April, fig. 4) indicates the Labrador 

 Current flowing southward over the steep slope 

 along the eastern edge of the Grand Banks, gen- 

 erally between the 500 and 2000 m isobaths. The 

 maximum geostrophic velocities in the current 

 ranged from 28-6.5 cm/sec at the different sec- 

 tions. Along the eastern edge of the survey area 

 the North Atlantic Current flowed northeastward 

 with speeds of 4.5-75 cm/sec. Between the two 

 currents was a large (130 km diameter) anti- 

 cyclonic eddy, centered at 44°30'N, 48°00'W. 

 The presence of the eddy was likely responsible 

 for a portion of the Labrador Current being 

 diverted to the east along the northern side of 

 the eddy. The warm core eddy probably wa^ 

 shed from the North Atlantic Current in a man- 

 ner similar to that observed on the north side of 

 the Gulf Stream (JSaunders, 1971). The tem- 

 peratures and geostrophic current across section 

 A3A (figs. 20n and c), which passed through the 

 eddy, indicate that the eddy structure e.xtended 

 at least to 1000 m depth. If a significant sec- 

 ondary circulation was driven by viscous forces 

 within the eddy, the secondary flow at the surface 

 would be radially outwards. The implication 

 would Ik- that icebergs would tend to remain on 

 the perii>hery of th^ eddy and not l)e drawn to 

 the eddy interior. 



The Labrador Current during the second sur- 

 vey (21-25 May), as revealed by the dynamic 

 topography (fig. 5). changed little from the first 

 survey. The anticyclonic eddy appeared to have 

 moved southeastward and rejoined the North 

 Atlantic Current, although the limited nature of 

 the survey precludes full delineation of the fea- 

 ture. This soutiieastward movement of the eddy 

 approximately paralleled to local bottom topog- 

 raphy, which would be expected for bathymetric- 

 ally controlled eddy movement (Warren, 1967). 

 Estimation of the speed of the movement is diffi- 

 cult since the eddy could have intersected the 

 North Atlantic Current at any time between the 

 surveys. The displacement of the eddy /meander 

 center over the time between the surveys yields 

 a speed of only 1 cm/sec. 



The dynamic topography for both intensive 

 surveys (figs. 6 and 8) indicate the Labrador 

 Current flowed south over the steep continental 

 slope, as is normally observed. Both also indi- 

 cate that the North Atlantic Current entered the 

 area from the southeast, turned clockwise, and 

 exited to the northeast. The major change which 

 occurred in the 8-10 days between the observa- 

 tions was that the dynamic trough between the 

 Labrador Current and the North Atlantic Cur- 

 rent deepened (970.92 dyn m to 970.88 dyn m) 

 and extended southward. The standard sections 

 occupied between the intensive surveys (fig. 7) 

 suggest that the curving of the North Atlantic 

 Current in figs. 6 and 8 was part of an eddy/ 

 meander feature similar to that observed in the 

 April surveys. 



The standard sections occupied in February. 

 August, and November do not allow contouring 

 of the dynamic topography due to the large 

 spatial separation between the sections. The 

 dynamic height values for each survey are plotted 

 in figs. 9, 10, and 11, with the direction of the 

 surface geostrophic current indicated by an 

 arrowhead. 



LABRADOR CURRENT TRANSPORT 



The spatial and temporal variations of the 

 transport of water by the Labrador Current may 

 be investigated by comparing the calculated geo- 

 strophic volume transports at the various sections 

 occupied. Due to inherent inaccuracies in the 

 method of ralrulation. tlie variations are likely 

 significant only in their general ti-end and not in 

 their exact magnitude. The minimum tempera- 



