traverse of a large eddy would be marked by a 

 sudden decrease of temperature and salinity due 

 to the influx of Subarctic Water. 



The influence of the North Atlantic Current, 

 as it varies in strength and distance from OS 

 DELTA, can be monitored by a change in the 

 physical properties of the water in the vicinity 

 of OS DELTA. Data gathered from stations 

 occupied during the period covered by this report 

 have been investigated for significant temporal 

 variations as an indication of the influence of 

 the North Atlantic Current. 



Attention is directed to the USCGC HAM- 

 ILTON cruise of 6-9 July 1968 (figs. 36 and 

 49) and specifically to stations 5, 9, and 13, 

 separated by intervals of 23.5 and 30.2 hours. 

 Station five showed the reduced influence of 

 North Atlantic Central Water (NACW), possibly 

 due to an increase in intensity and /or a southeast 

 movement of the North Atlantic Current. An 

 apparent return of NACW was registered during 

 occupation of station 13. 



Observations made during the cruise of the 

 USCGC INGHAM (figs. 26 and 39) at stations 

 2,3, and 4 showed temperature and salinity values 

 indicative of NACW. Station 7, four days later, 

 indicated temperature and salinity minima in the 

 upper 800 meters as the Polar Front shifted 

 position towards OS DELTA. 



Similar distributions of properties were ob- 

 served during the September 1967 cruise of 

 USCGC CHINCOTEAGUE (figs. 27 and 40), May 

 1968 cruise of USCGC DALLAS (figs. 34 and 

 47), March 1968 cruise of USCGC ABSECON 

 (figs. 32 and 45), and July 1968 cruise of USCGC 

 DALLAS (figs. 37 and 50). 



Due to relatively few "off station" casts, little 

 can be evaluated concerning horizontal variations 

 in physical properties. Separations were limited 

 to 70 nautical miles in latitude with corresponding 

 temperature and salinity differences of 1.0C° and 

 0.5%o in the upper 50 m. Variations in tempera- 

 ture and salinity were not observed with longitu- 

 dinal differences of up to 90 nautical miles. 



The physical properties observed at OS DELTA 

 and those of the surrounding water masses can 

 best be compared by examining the observations 

 made at OS DELTA, OS ECHO, OS CHARLIE, 

 and selected stations along SSA3 (fig. 1). Obser- 

 vations at OS CHARLIE describe the water 

 masses peculiar to the subarctic; properties ob- 

 served at OS ECHO detail NACW characteristics, 

 and observations along SSA3 provide insight into 

 properties unique to the North Atlantic Current. 



Comparison of temperature and salinity vertical 

 distributions at the above locations was made for 

 February and August 1968 (figs. 52 and 53). 



Data from SSA3 and OS DELTA exhibit isoha- 

 line/ isothermal layers down to about 100 m 

 during February, with the greater depths display- 

 ing similar trends in their distributions. The 

 nearly uniform distribution of Subarctic Water 

 (especially at OS DELTA, OS CHARLIE, and 

 SSA3) below 800 m becomes clear and is supported 

 by the close coincidence of temperature and salin- 

 ity vertical distributions. 



During August, observations at SSA3 and OS 

 DELTA showed similar characteristics of temper- 

 ature and salinity versus depth, with the forma- 

 tion of definite thermoclines and haloclines down 

 to 100 m. As is typical of subarctic zones, salinity 

 increases slightly with depth at OS DELTA and 

 SSA3, but maximum salinities are observed at 

 the surface of OS ECHO (subtropic location). 



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