Oceanography of the Grand Banks Region of 

 Newfoundland m 1967 



Bij Charles W. Morgan, U.S. Coast Guard 



INTRODUCTION 



Ice Patrol cruises in 1967 continued the 

 practice initiated in 1966, in that three section 

 surveys replaced the old area survey method 

 (Wolford, in press). Calibrating the normal 

 topography is the term for comparing the sur- 

 face dynamic heights at these three standard 

 sections with the charts of average monthly 

 surface dynamic topography off the Grand 

 Banks prepared by Soule (1964). Figures 1, 

 3, and 5 show the standard sections occupied. 

 The reason for the change to calibration sur- 

 veys is that research shows large short-term 

 (1- to 2-week) fluctuations in the volume flow 

 of the Labrador Current, and therefore, cali- 

 bration type surveys, frequently repeated, give 

 better data for the prediction of iceberg move- 

 ment in the Grand Banks area, as well as re- 

 duce the ship time necessary for routine sur- 

 veying. 



The time required for a calibration survey 

 varies from 4 to 7 days. This compares with 

 about 7 days for the 1965 cruises which used 

 a modified area survey and the pre-1965 cruises 

 which required about 14 days for an area 

 survey. 



NARRATIVE 

 General 



The USCGC EVERGREEN (WAGO-295), 

 a 180-foot oceanographic vessel, made three 

 cruises to the Grand Banks in the spring and 

 summer of 1967. Real-time oceanographic sup- 

 port was furnished to Commander, Interna- 

 tional Ice Patrol on the first two cruises. The 

 third cruise was a post-season research cruise 

 in late July. 



The first cruise lasted from 28 March to 1 

 May 1968. Weather, sea, and ice conditions 

 were bad, and on occasion forced the CGC 

 EVERGREEN to heave to. During 2 to 8 

 April the CGC EVERGREEN made a calibra- 

 tion survey of standard sections A2, A3, and 

 A4, occupying stations 9849-9893. After com- 

 pletion of the survey the ship reoccupied 

 standard section A3 on 9 April with stations 

 9884-9890. The period from 10 to 21 April 

 was devoted to iceberg drift studies and to 

 putting in to Saint John's and Argentia, New- 

 foundland. A time-series study of standard 

 section A3 commenced on 22 April with station 

 9891. This section was occupied four times 

 during the time-series study. A pair of ref- 

 erence markers, which were later lost in a 

 storm before the fourth time-series occupation, 

 marked the western end of the section. During 

 the reoccupation on 25 April, expendable BT 

 casts were made every mile to define details 

 of temperature structure. The STD shorted out 

 during station 9911 necessitating the use of 

 Nansen casts for the rest of the cruise. On 

 27 April the CGC EVERGREEN completed 

 station 9916 and set sail for Boston with the 

 first cruise of the season behind her. 



After departing Boston on 8 May for the 

 second cruise, the CGC EVERGREEN began 

 a survey of standard section A2, A3, and A4 

 on 12 May with station 9917. Completing sta- 

 tion 9949, the calibration survey was finished 

 on 15 May, and the CGC EVERGREEN com- 

 menced an iceberg drift study which lasted 

 until 20 May. A second time-series study was 

 then initiated on standard section A3 with 

 reference markers again placed at the western 

 end of the section. The four occupations of 



