CHAPTER 5 



greater than any other month. However, in 1976, an ab- 

 normally high discharge rate was recorded during Feb- 

 ruary, and was largely sustained into May. Thus, near- 

 surface waters, especially at station 23, should show un- 

 usually low salinity with correspondingly greater stratifi- 

 cation. This is in part corroborated by the April high- 

 density ratio (1976/1975) value of 15 at station 23 (table 

 1). The April and May 1976 salinity differences (fig. 5-7) 

 are relatively higher than in 1975, implying that the dis- 

 charge of the Hudson River was either greater or more 

 confined to the Bight Apex during 1976. 



DISSOLVED OXYGEN 



In April 1976 surface oxygen values were higher and 

 bottom oxygen values lower than in April 1975 (fig. 5-8). 

 Consequently, oxygen stratification was pronounced by 

 April 1976, but a well-mixed condition existed in April 

 1975. Stratification development was not apparent until 

 June or July 1975. 



As summer progressed, surface oxygen decreased in 

 both years, but generally continued over 100 percent sat- 

 uration. The only exception was at station 88, where sur- 

 face oxygen values fell slightly below lOU percent satu- 

 ration during July, August, and September 1975. 



As summer advanced in both years, bottom oxygen val- 



ues decreased at rapid rates, but the 1976 rate was con- 

 siderably greater. (See chapter 4.) 



SUMMARY 



Seasonal density stratification began about 1 month ear- 

 lier in 1976 than in 1975 (April vs. May), because of early 

 seasonal heating (thermal stratification) and, more im- 

 portantly, strong and sustained river discharge (salinity 

 stratification). Subsequently, the rate of bottom replen- 

 ishment of dissolved oxygen from the sea surface was less 

 than that of 1975. 



ACKNOWLEDGMENTS 



Adriana Cantillo and Dennis Mayer of ERL/AOML 

 and Steacy Hicks of NOS provided necessary data. The 

 following individuals contributed data sets used in the 

 analysis: Tom Azarovitz of NMFS, Woods Hole; Art Ken- 

 dall, Frank Steimle, and W. G. Smith of NMFS, Sandy 

 Hook; Frank Aikman of Lamont-Doherty Geological 

 Observatory; and E. P. Ruzecki of Virginia Institute of 

 Marine Science. D. V. Hansen made helpful suggestions. 

 The officers and crew of NOAA ships George B. Kelez 

 and Researcher devoted long and diligent hours in ac- 

 quiring data. 



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