The station spacing was controlled by radar 

 ranges and bearings taken periodically on the 

 reference buoy. Because only one reference 

 buoy was used, the orientation of the sections 

 could not be exactly reproduced, and from the 

 bottom topography it is believed that the first 

 section was to the north of the last two. The 

 vertical temperature and salinity structure for 

 these three partial occupations are shown in 

 Figures 33 through 38. A plot of the surface 

 dynamic heights observed during each occupa- 

 tion is shown in Figure 32. Charts of the dy- 

 namic topography observed during these 

 occupations are shown in Figures 2A, 2B, and 

 2C. 



During these three occupations the shelf 

 dynamic height value increased continuously 

 while the trough value decreased. At first it 

 was thought this might have been normal 

 spring infusion of colder, fresher water. Fig- 

 ures 33 through 38 show a freshening oc- 

 curred, but both the mean temperature and 

 the mean salinity remained higher than nor- 

 mal. During 16-17 April the minimum temper- 

 ature observed was 1.48° C at the bottom of 

 station 9535 and the minimum salinity was 

 33.54%,, at the surface of station 9536. 



The 18-19 April partial occupation showed 

 a continuing cooling and freshening. The 

 minimum temperature 1.19° C and the mini- 

 mum salinity 33.50%o both occurred at station 

 9543. They were just east of the continental 

 shelf edge and they were in the southerly cur- 

 rent. During the 21 April 1966 partial occupa- 

 tion of Standard Section 3 the water was more 

 saline than during either of the previous oc- 

 cupations. The minimum temperature was 

 1.37° C and the minimum salinity was 33.56%o. 

 Both of these values were observed at a station 

 on the Grand Banks. All three occupations 

 showed anomalously high values of tempera- 

 ture and salinity when compared with the 

 typical vertical cross sections of 1964 and 

 1954. 



Figure 32 shows that the dynamic topo- 

 graphy changes significantly with time. It is 

 realized that these variations are a combina- 

 tion of the local time rate of change plus 

 changes due to slight horizontal displacement 

 of the station positions. Comparison of the sur- 

 face dynamic heights observed from these 

 three occupations with those of the 4-5 April 



1966 occupation showed that the dynamic 

 heights of the stations located on the continen- 

 tal shelf had increased by three dynamic centi- 

 meters in 12 days. The trough had deepened 

 from 970.97 to 970.90 dynamic meters, a 

 change of 7 dynamic centimeters. This value 

 was closer to the average trough value of 

 970.924 dynamic meters calculated by KoUmeyer 

 et al, 1965. This return to a near normal trough 

 value coincided with the disappearance of the 

 intrusion of 7° C water of atypical character 

 observed previously. 



These three serial occupations showed that 

 significant property changes can occur over a 

 relatively short time interval. They also showed 

 that a return to a normal dynamic height 

 topography did not require the cold tempera- 

 ture usually found in the core of the Labrador 

 Current. 



CGC EVERGREEN 25-26 MAY 1966 

 OCCUPATION OF STANDARD SECTION 3 



The next occupation of Standard Section 3 

 occurred on 25-26 May 1966. The surface dy- 

 namic heights along the section are shown in 

 Figure 39. The vertical temperature and salin- 

 ity structures are shown in Figures 40 and 41. 



A comparison of Figures 32 and 39 shows 

 that the trough values have remained rela- 

 tively unchanged, but the western station 

 value has decreased from 971.106 to 971.012 

 dynamic meters, a significant decrease of ap- 

 proximately 9 dynamic centimeters. From the 

 trough the dynamic topography slopes gently 

 upward to the east to a maximum value of 

 971.131. Again the 7.0° C isotherm intruded 

 westward to station 9572. The warm water 

 mass found in the surface layer at station 

 9573 had atypical temperature-salinity char- 

 acteristics. The minimum temperature of 

 0.92° C and the minimum salinity of 33.10%o 

 both occurred at station 9570. Since the mean 

 temperature of the inshore station had in- 

 creased, the factor that contributed to the 

 lower than normal value for dynamic heights 

 must be the persistently high salinity values 

 on the continental shelf. 



As during the previous occupations the tem- 

 peratures in the core of the Labrador Current 

 were anomalously warm and the southward 

 flow of cold water was smaller than expected. 



11 



