Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 5. Physical Conditions Compared With 



Previous Years 



John B. Hazelworth and Shailer R. Cumniings' 



CONTENTS 



Page 



125 Introduction 



126 Density (sigma-t) 

 129 Temperature 



129 Salinity 



135 Dissolved Oxygen 



135 Summary 



135 Acknowledgments 



' Atlantic Oceanographic and Meteorological Labo- 

 ratories, Environmental Research Laboratories, NOAA, 

 Miami, FL 33149 



INTRODUCTION 



Dissolved oxygen content of water in New York Bight 

 has an annual cycle. In general, it reaches its well-mixed 

 maximum during the winter, then gradually decreases dur- 

 ing spring, dropping to its minimum during summer. The 

 minimum is considerably lower at the bottom than at the 

 surface. In the autumn, cold air and storms cool surface 

 water, break down the thermocline, introduce oxygen into 

 the water, and cause mixing to greater depths. The oxygen 

 content in the water increases until it again reaches its 

 maximum during winter. The causes of the autumnal oxy- 

 gen increases are physical and fairly well understood. The 

 processes causing the spring and summer oxygen decline, 

 however, are not as well understood. Apparently, atmos- 

 pheric, biological, and chemical processes combine with 

 physical processes to bring about the oxygen decrease. 



To compare 1976 physical conditions with those of pre- 

 vious years, physical data were obtained from several 

 sources: 



1. Seven MESA expanded water-column character- 

 ization (XWCC) cruises in 1975, four XWCC 

 cruises in 1976, and nine water-column character- 

 izion (WCC) cruises in 1974, all by NOAA's At- 

 lantic Oceanographic and Meteorological Labo- 

 ratories (AOML); 



2. Monthly mean sea-surface temperatures, com- 

 piled by NOAA National Marine Fisheries Serv- 

 ice's (NMFS) Atlantic Environmental Group 

 (AEG) from ship reports, and from data provided 

 by NOAA Environmental Data and Information 

 Service's National Climatic Center (NCC); 



3. Oceanographic data from Lamont-Doherty Geo- 

 logical Observatory of Columbia University; 



4. Oceanographic data from NMFS laboratories at 

 Sandy Hook, N.J., and Woods Hole, Mass.; 



5. Oceanographic data from Virginia Institute of 

 Marine Science (VIMS); and 



125 



