OCEANOGRAPHIC CONDITIONS, 1970 



(Provided by U.S. Coast Guard Oceanographic Unit) 



Two oceanographic cruises were conducted dur- 

 ing the Ice Patrol season aboard USCGC Ever- 

 green (WAGO 295). The dynamic topography of 

 the sea surface relative to the 1000 decibar sur- 

 face was obtained from these cruises (figures 14- 

 17). The most prominent feature of the circula- 

 tion was the Labiador Current flowing south- 

 ward along the eastern slope of the Grand Banks. 

 Farther east was the dynamic trough that sep- 

 arates the Labrador Current from the northwest- 

 ward flowing North Atlantic Current. 



Conditions found during the 1970 season dif- 

 fered somewhat from the normal or average con- 

 ditions. There was evidence of an additional dy- 

 namic low in the vicinity of 44N, 47W (figures 

 15 and 16). This low was caused by an unusual 

 clockwise dynamic high to the north at 45N, 47W 

 (figures 16 and 17). The features of this high 

 could be observed at least as deep as 1200 meters. 

 The Labrador Current had a particularly intense 

 geostrophic current (2.5 knots) on 31 May-1 

 June at 44— SON 48-50W. This occurred because 

 the sea surface in the trough fell 10 dynamic 



centimeters during the preceding 6 days. 



A detailed survey off the southeast slope of 

 the Grand Banks was made to determine the cir- 

 culation over the Newfoundland Rise. The charts 

 of normal dynamic topography do not adequate- 

 ly define the circulation of this region because of 

 its high variability. The circulation indicated by 

 the mass distribution was much more complicated 

 than expected (figure 16). There was a great deal 

 of difference observed in the circulation by two 

 oceanographic surveys of roughly the same area 

 (figures 15 and 16). These differences may result 

 from two factors. First, the circulation may have 

 changed during the interval between the two 

 surveys. Second, the section spacing was greater 

 on the first cruise than on the second, thus much 

 of the detail may have been lost on the first 

 cruise. 



A more detailed analysis of the oceanography 

 of the Grand Banks and the Labrador Sea in 

 1970 will be published in the U.S. Coast Guard 

 Oceanographic Report Series (CG-373). 



17 



