OCEANOGRAPHY OF THE GRAND BANKS REGION OF NEWFOUNDLAND 



APRIL-JULY 1974 



CHARLES R. WEIR 1 



INTRODUCTION 



During 1974 Ice Patrol Season the CGC 

 EVERGREEN (WAGO-295) conducted two 

 oceanographic cruises near the Grand Banks of 

 Newfoundland (Fig. 1). These studies aided 

 Commander, International Ice Patrol (CUP) by 

 providing him with real-time ocean current 

 analysis. Experiments were also conducted to 

 study the effect of ocean currents and wind on the 

 drift of icebergs and to measure ocean currents 

 directly with the use of current meters. 



The geostrophic component of the surface 

 currents was computed from salinity and 

 temperature data collected with an S/T/D 

 Environmental Profiling System (STD). A level of 

 no motion was assumed at 1000 meters. In water 

 shallower than this depth, STD casts were taken as 

 close to the bottom as practicable, normally 20 

 meters. All data were processed real-time aboard 

 ship using a Digital Data Logger/Computer 

 System and the evaluated current information was 

 transmitted to CUP. The method of calculating the 

 dynamic height for each station is described by 

 Kollmeyer, et al. (1967). 



8-15 APRIL CGC EVERGREEN SURVEY 



From 8 April to 15 April the USCGC 

 EVERGREEN conducted a survey along Standard 

 Sections A3, A2B, A2A, and A2 mod. (Fig. 2). 

 Fifty-two STD stations corresponding to Ice 

 Patrol Station numbers 11491 through 11542 were 

 occupied. The Labrador Current can normally be 

 found flowing along the eastern edge of the Grand 

 Banks (Scobie and Schultz, 1976). During this 

 survey a portion of the Labrador Current was 

 found to be flowing easterly, south of Flemish Cap. 

 In addition the trough, or area that separates the 

 North Atlantic Current and the Labrador Current, 

 was unusually wide when compared to the normal 

 pattern. For the southerly flowing portion of the 

 Labrador Current, the maximum surface current 



was calculated to be 47.5 cm /sec between station 

 11495 and 11496. The volume transport between 

 these stations was 1.56 Sverdrups. This is 

 comparable to past April surveys. That portion of 

 the Labrador Current flowing eastward, south of 

 Flemish Cap has a maximum calculated current of 

 6 cm/sec between station 11519 and 11520. 

 Although this was not a very strong current, it 

 could have caused an iceberg to drift about 3 

 nautical miles per day. 



At about 44°30'N, 45°30'W the North Atlantic 

 Current divided into two separate patterns. The 

 northerly arm of this warmer current was greatly 

 intensified by the end of the month as was shown 

 by the next survey. The maximum current velocity 

 of the northerly area was 14.5 cm/sec between 

 stations 11518 and 11519. Between stations 11504 

 and 11505 the current was calculated to be 47 

 cm/ sec. 



The volume transport of the southward flowing 

 Labrador Current was as follows: 



29 APRIL-1 MAY 



CGC EVERGREEN SURVEY 



During this survey Standard Sections A2A and 

 A2 mod were completed in addition to a special 

 section connecting these standard sections: SSI. 

 Thirty-six STD stations consisting of Ice Patrol 

 Stations 11547 through 11578 were occupied. The 

 purpose of the special section was to better 

 measure the eastward flowing Labrador Current 

 south of Flemish Cap. As can be seen from figure 

 3, the current system was more complicated 



1 U.S. Coast Guard Oceanographic Unit, Bldg. 159-E, 

 Navy Yard Annex, Washington, D.C. 20593. 



