Oceanography of the Grand Banks Region 

 and the Labrador Sea 



April-June and October 1968 



Henry S. Andersen > and Martin J. Moynihan ' 



INTRODUCTION 



This description of the physical oceanography 

 of the Grand Banks Region and the Labrador 

 Sea for 1968 is based on three International Ice 

 Patrol cruises to the Grand Banks of New- 

 foundland from April through June, and an 

 occupation of a section from South Wolf Island, 

 Labrador to Cape Farewell, Greenland in late 

 October. 



The oceanographic cruises in support of the 

 International Ice Patrol during the spring of 

 1968 were conducted by USCGC EVERGREEN 

 (WAGO 295), Commander Arthur J. Solvang, 

 USCG, Commanding. These cruises followed 

 the practice of the two preceding years in that 

 surveys were conducted along three standard 

 monitoring sections for the purpose of cali- 

 brating Soule's (1964) normal dynamic topog- 

 raphy charts. The sections were occupied in 

 rapid sequence during three cruises to furnish 

 real-time analysis of the marine environment 

 to Commander, International Ice Patrol for the 

 prediction of iceberg movements in the Grand 

 Banks region. Additional stations were occupied 

 in the area southeast of the Grand Banks to 

 locate and describe the semipermanent meander 

 of the Nortii Atlantic Current, which has a 

 significant effect on the strength and location 

 of the Labrador Current. 



The first cruise left Boston, Mass., on 29 

 March 1968 and returned on 27 April. Three 

 surveys of Standard Sections A2, A3 and A4, 

 consisting of Ice Patrol stations 10041 through 

 10147 (for convenience, the first two digits of 

 the station numbers are not used in the ac- 

 companying figures), were completed between 

 2 and 24 April 1968. During the period 17-20 

 April, the USCGC EVERGREEN visited Saint 

 John's, Newfoundland. 



On the second cruise, which lasted from 7 

 May to 4 June 1968, the USCGC EVERGREEN 

 occupied stations 10148 through 10254, com- 



pleting three occupations of Standard Sections 

 A2 and A3 and a single occupation of Section 

 A4. This cruise was marked by severe weather 

 and sea conditions which forced the ship to 

 heave-to for a total of 91 hours. It was necessary 

 to put into Argentia, Newfoundland on 27 May 

 1968 to replenish the fresh water supply and 

 avoid the heavy weather. 



During the second cruise, on 11 May 1968, 

 an oceanographic buoy system was established 

 in the Labrador Current in 500 fathoms of 

 water east of the Grand Banks at 45°02.5'N, 

 48°53'W. A current meter and temperature re- 

 corder were attached to a tautline moor from a 

 subsurface buoy. A depth-positioning device 

 was incorporated into the system to position the 

 recording instruments at a depth of approxi- 

 mately 75 meters. The mooring system consisted 

 of one-quarter inch "Al-u-flex" cable attached 

 with anchor chain to a 6000 pound concrete 

 sinker. Two mechanical time releases were con- 

 nected in parallel and set to release the sub- 

 surface buoy on 24 June 1968. The location of 

 the system was marked by a toroidal surface 

 buoy connected to the subsurface buoy by a 

 500-foot pendant of %" nylon line. Both buoys 

 were equipped with lights. 



After the buoy system had been moored for 

 about one hour, the subsurface buoy surfaced 

 unexpectedly. During the next 35 hours, the 

 positions of the buoys were monitored and a 

 series of 26 oceanographic casts (stations 10148 

 through 10173) were made adjacent to them. 

 The surveillance of the buoys indicated they 

 were still on station, leading to the conclusion 

 that a malfunction of the depth-positioning 

 device was the most probable cause of the sur- 

 facing of the subsurface buoy. The buoy system 



' U.S. Coast Guard Oceanographic Unit, Washington, 

 D.C. 20390. 



