reached a maximum of 34. 84 °/oo- Freshening of 

 the upper portion of the water column occurred 

 until a surface salinity minimum of 34.04°/oowas 

 attained in July 1968 (fig. 40). The seasonal 

 increase of the surface salinity reached a max- 

 imum of 35.607ooin April 1969 (fig. 52). Sea- 

 sonal freshening then occurred again until a sur- 

 face minimum of 34. 10°/oo occurred in September 

 1969 (fig. 59). 



Selected levels of monthly temperature aver- 

 ages are shown for January 1964 through 

 November 1969 (fig. 62). The variations from 

 January 1964 through September 1967 have al- 

 ready been discussed (Shuhy 1969). The same 

 annual variations continued through 1968 and 

 1969 as in previous years, however the minimum 

 surface temperatures during November 1967 

 through November 1969 were about 1°C cooler 

 than during the 1964-1967 period. 



A monthly average surface salinity maximum 

 of 34.8l7oooccurred in February 1968 (fig. 63) 

 after which time the surface waters began to 

 freshen until a minimum of 34.31°/oowas ob- 

 served in August 1968. After August 1968 the 

 surface waters became more saline until a max- 

 imum of 34.557oowas attained in April 1969. 

 This maximum of 34.55°/oowas only 0.03°/oosal- 

 tier than the minimum salinity of 34.52°/ooob- 

 served during the months of August and Sep- 

 tember during the previous four years (annual 

 range of average surface salinity was 0.28%oin 

 1967). The average surface salinity then de- 

 creased to a low of 34.25°/ooin September 1969; 

 this was 0.2 7 °/oo fresher than has been observed 

 since 1964 when the program of oceanographic 

 observations started on O.S. BRAVO. 



The seasonal cooling cycle of the surface wat- 

 ers at Ocean Station BRAVO begins in the 

 months of August and September. As the surface 

 temperature decreases, the surface water be- 

 comes more dense and sinks mixing with the 

 deeper more saline water, thereby causing the 

 surface water to become more saline. This mixing 

 by the anomalously fresh surface water at 



BRAVO in the summer of 1968 also caused the 

 deeper water to become noticeably fresher than in 

 previous years. The anomalously tresh water that 

 was observed at the surface in August 1968 was 

 observed at the 50 meter level in November 1968, 

 at the 100 meter level in January 1969 and the 

 200 meter level two months later in March 1969. 

 It appears as though there may have been a slight 

 influence of the surface waters at the 300 and 400 

 meter levels. 



The water column was nearly isopycnal (27.75 

 sigma-t) to a depth of 400 meters from about 

 January to April during 1964 through 1968 (fig. 

 64), indicating that the surface waters had 

 thoroughly mixed down to that depth. Howevei, 

 such was not the case in 1969. The extremely low 

 surface salinities in 1968/1969 did not allow the 

 surface waters to become as dense as previous 

 years. This slowed down the vertical mixing proc- 

 ess and resulted in a stratification of density in the 

 upper 400 meters. 



If the phenomenon of low surface salinities 

 accompanies colder surface temperatures, the 

 overall result would be less dense surface water at 

 BRAVO which would discourage the formation of 

 North Atlantic Deep and Bottom water in this 

 vicinity. 



REFERENCES 



Husby. D. M. (1967). Oceanographic Observations at 

 North Atlantic Ocean Station BRAVO, August 

 1964-Noveniber 1965, U.S. Coast Guard Oceano- 

 graphic Data Report, CG 373-9. 



Husby, D. M. (1968). Oceanographic Observations, North 

 Atlantic Ocean Station BRAVO, October 1965-1966. 

 U.S. Coast Guard Oceanographic Report, CG 373-14. 



McGary, J. W. (1965). Oceanographic Observations at 

 North Atlantic Ocean Station BRAVO, January-April 

 1964. U.S. Coast Guard Oceanographic Report, CG 

 373-7. 



Shuhy, J. L. (1969). Oceanographic Observations at North 

 Atlantic Ocean Station BRAVO. October 1966-October 

 1967. U.S. Coast Guaid Oceanographic Report, CG 

 373-20. 



