OCEANOGRAPHY OF THE GRAND BANKS REGION 

 OF NEWFOUNDLAND 



APRIL-AUGUST 1971 

 ALAN DALE ROSEBROOK' 



INTRODUCTION 



Three cruises were conducted to the Grand 

 Banks of Newfoundland during 1971 to study 

 the circulation of the region (fig. 1). The 

 oceanographic cruises were conducted in support 

 of Commander International Ice Patrol for use 

 in predicting iceberg drift into the Xorth At- 

 lantic. The study included liydrographic sur- 

 veys, direct current measurements using para- 

 chute drogues, and direct current measurements 

 from taut-line instrumented arrays set at 46°- 

 40'N., 47"24'W. and 45°02'N., 48°55'W. 



April EVERGREEN Survey 



During the first Ice Patrol cruise aboard 

 USCGC EVERGREEX (WAGO 295), a survey 

 consisting of standard sections A2 and A3, and 

 special sections A2A, A2B, A3B, and Si was 

 completed (fig. 2). Seventy STD stations, con- 

 sisting of Ice Patrol stations 10808 through 

 10877, were occupied. The sections were occupied 

 in rapid sequence to furnish real-time analysis 

 of the current regime along the eastern edge of 

 the Grand Banks region. Commander Interna- 

 tional Ice Patrol utilized this information for tiie 

 prediction of iceberg movements. 



May Multishlp Survey 



During the first half of the second cruise, 

 technicians from Woods Hole Oceanographic 

 Institution (WHOI) established a subsurface 

 oceanogra[)hic buoy array near 39°52'X., 48°32'W. 

 to pi'ovide direct current measurements near the 



1. U.S. Coast Guard Oceanographic Unit, Bldg. 1.59-E, 

 Navy Yard Annex, Washington, D.C, 20390. Presently 

 Comni.indinK OfTicer, USCGC MESQUITE (WLH 30.'), 

 Sturgeon Bay, Wis., 542.35. 



ocean bottom. An expendable bathythermograph 

 survey was conducted by WHOI for two days 

 to chart the northern boundary of the Gulf 

 Stream by following the 15.0°C isotherm at a 

 depth of 200 meters. 



On 11 ]May 1971, the Coast Guard Oceano- 

 graphic Unit (CGOU) field party established 

 an oceanograjihic buoy system in the Labrador 

 Current. The array was set in 198 meters of 

 water at 45°02'N., 48°55'W. A second buoy 

 system was set on 12 May 1971 in the Labrador 

 Current in 205 meters of water at 46°40'N., 

 47°24'W. The current meter arrays were de- 

 signed by adopting and modifying a basic suc- 

 cessful array developed by WHOI (Berteaux 

 and Walden, 1969). A detailed discussion of the 

 design, construction, and deployment of the 1971 

 buoy arrays is presented in CGOU Technical 

 Report 72-1 (Vais et al., 1972). Prior to a port 

 call in St. John's, Newfoundland, EVERGREEN 

 occupied the east-west leg of standard section 

 A2, consisting of Ice Patrol stations 10878 

 through 10884. 



EVERGREEN occupied standard section A2 

 once, the east-west leg of A2 on two occasions, 

 and si^ecial sections AlC, AlB, and A2A (Ice 

 Patrol stations 10885 through 10944). On 25 

 May, the northern CGOU buoy array was suc- 

 cessfully recovered. Attempts to retrieve the 

 southern array were futile. Although the surface 

 float was missing, the acoustic release responded 

 to interrogation when EVERGREEN was di- 

 rectly over the buoy position, leading to specula- 

 tion that one of the many fishing vessels operat- 

 ing in the area may have accidentally cut the 

 surface float loose during one of the frequent 



