position and depth log for all hydrographic and 

 XBT stations. This log was periodically re- 

 viewed by USCGC EVERGREEN personnel. 



DATA PRESENTATION 



Data Listings 



The STD traces were read at the standard 

 depths of 0, 10, 20, 30, 40, 50, 75, 100, 150, 

 200, 250, 300, 400, 500, 600, 700, 800, 1,000, 

 1,100, 1,200, 1,300, 1,400 and 1,500 meters, and 

 at all inflection points. These data, along with 

 the dissolved oxygen, chlorophyll, time, posi- 

 tion, meteorological, and sea surface data were 

 entered on the NODC Form for Reporting 

 Electronically Obtained Serial Data. These 

 forms were submitted to the National Ocean- 

 ographic Data Center, which later provided 

 printed data listings. In addition to the data 

 submitted, the printed listings also contain 

 values for Sigma-t, specific volume anomaly, 

 dynamic height, and sound velocity computed 

 at NODC. The printed data listings for the 

 September and December cruise are contained 

 in Tables I and II of Appendix A. 



Surface Contours 



Surface values of temperature, salinity and 

 Sigma-t were plotted along the cruise track, 

 and surface contours were produced from these 

 values. Surface isotherms, isohalines and 

 isopycnals for September and December are 

 presented in Figures 3 through 8. 



Vertical Sections 



Vertical sections for temperature, salinity, 

 Sigma-t, oxygen, and chlorophyll were drawn 

 for both cruises. The sections were drawn for 

 those legs of the cruise track which were ap- 

 proximately normal to the coastline (figs. 1 

 and 2). For a meaningful presentation of 

 vertical section contours, the vertical distance 

 scale has been greatly exaggerated in com- 

 parison to horizontal distance scale (135:1). 

 Sections of temperature, salinity and Sigma-t 

 were drawn to a maximum depth of 500 

 meters. Temperature contours for the Septem- 

 ber and December cruises (figs. 9-24) were 

 constructed using all of the sources of tem- 

 perature data (STD, reversing thermometers 

 and XBT's) collected on these cruises. Salinity 

 sections (figs. 25-40) and Sigma-t sections 

 (figs. 41-56) were also drawn to a maximum 



depth of 500 meters. The sections of dissolved 

 oxygen (figs. 57-71) were drawn to a maxi- 

 mum depth of 250 meters and those of chloro- 

 phyll (figs. 72-86) were drawn to a maximum 

 depth of 100 meters. 



Water Masses 



Vertical sections of temperature and salinity 

 were inspected to determine the existence of 

 water masses having characteristic properties 

 of temperature or salinity. Isotherms and 

 isohalines which tended to form closed loops on 

 the vertical section contours were considered 

 to be the boundaries of water masses. When 

 "closed loop" isotherms (or isohalines) of iden- 

 tical value appear on successive sections, they 

 were joined together by smooth lines to give 

 a three dimensional perspective of the water 

 masses (figs. 87-90). These figures are not a 

 synoptic portrayal of the shape of the bound- 

 aries, but rather represent the extent of the 

 boundaries over the time period of the cruise. 



RESULTS 

 Temperature Distribution 



The physical properties of coastal waters of 

 the Mid-Atlantic Bight are subject to large sea- 

 sonal variations. In September surface waters 

 over the shelf ranged from 17^C to 20°C and 

 subsurface waters were 2C° to 40° cooler. In 

 December the shelf water was essentially 

 vertically isothermal and ranged from 6°C to 

 10°C. 



Using data from various sources, Bigelow 

 (1933) gave a description of the temperature 

 cycle for the Mid-Atlantic Bight waters. Sur- 

 face cooling and intense mixing of the vertical 

 column occur over the shelf during the winter 

 months. Shelf water temperatures reach a 

 minimum during February and March. This 

 minimum is followed by vernal warming oc- 

 curring more rapidly inshore and at the sur- 

 face. A thermocline of increasing steepness is 

 developed as the warming season progresses. 

 The thermocline is steepest in mid-September, 

 after which autumnal cooling begins and the 

 cycle is repeated. Daily water temperature and 

 .salinity at 13 locations along the Atlantic sea- 

 board were tabulated for 1966 and 1967 by 

 Chase (1969). The temperature cycles are 

 depicted graphically in an atlas of monthly 



