Expendable Bathythermograph Observations From 

 the NMFS/MARAD Ship of Opportunity Program 



for 1974 



STEVEN K. COOK and KEITH A. HAUSKNECHT 1 



ABSTRACT 



Results of the fourth year of operation of the NMFS/MARAD Ship of Opportunity Program 

 (SOOP) are presented in the form of vertical distributions of temperature and horizontal dis- 

 tributions of sea surface temperature and salinity. Operational and data management procedures also 

 are discussed. Included are descriptive analyses of the most dynamic transects showing the Yucatan, 

 Loop, Florida, and Gulf Stream currents and related eddies. Also, characteristics of the cold cell of 

 bottom water on the Atlantic continental shelf are discussed. 



INTRODUCTION 



In midyear of 1970 a cooperative expendable bathy- 

 thermograph (XBT) program was initiated between the 

 National Marine Fisheries Service (NMFS) and the 

 Maritime Administration (MARAD) of the U.S. Depart- 

 ment of Commerce (Cook 1973, 1975, 1976). The 

 program, conducted in support of the Marine Resources 

 Monitoring Assessment and Prediction Program (MAR- 

 MAP) of the NMFS, involved the use of maritime cadets 

 from the Kings Point Maritime Academy to collect XBT 

 data on board merchant ships operating along the east 

 and Gulf coasts of the United States. The objective of 

 this cooperative program was to identify and describe 

 seasonal and year-to-year variations of temperature and 

 circulation in the major current regimes of the western 

 tropical Atlantic, Caribbean Sea, Gulf of Mexico, and 

 western North Atlantic, utilizing merchant ships as 

 relatively inexpensive platforms for the collection of 

 data. 



AREAS OF STUDY 



Ship routes were selected to obtain regular sampling in 

 the most dynamic areas of the Gulf of Mexico and 

 western North Atlantic. The features of principal in- 

 terest were the Yucatan Current, Loop Current, Florida 

 Current, Gulf Stream, Shelf Water-Slope Water front, 

 and a cold-water cell in the Middle Atlantic Bight. 



DATA ACQUISITION AND PROCESSING 



The Ship of Opportunity effort for 1974 consisted of a 

 total of 34 cruises — 18 sailing from New Orleans, 12 from 

 New York, and 4 from Norfolk. Fifty-three transects of 

 subsurface temperature observations and associated sur- 



'Atlantic Environmental Group, National Marine Fisheries Service, 

 NOAA, R.R. 7A, Box 522-A, Narragansett, RI 02882. 



face data were obtained. A total of 739 XBT's were 

 launched; of these 514 (70%) were considered of suf- 

 ficient quality to be incorporated into the transects 

 presented. 



Subsurface temperature data were obtained by use of 

 Sippican XBT systems. At the same time, surface water 

 samples were collected with bucket thermometers for 

 salinity determination ashore using a Beckman induc- 

 tive salinometer calibrated with standard (Copenhagen) 

 water at least once every 30 samples. 



The XBT traces were submitted to the National 

 Oceanographic Data Center (NODC) where they were 

 digitized, key punched, and quality controlled. Finally, 

 these processed data were listed in printout form and 

 machine plotted. The plots produced by NODC were es- 

 sentially camera-ready and needed little hand cor- 

 recting. The few corrections necessary were made by dis- 

 carding anomalous XBT observations that could not be 

 supported by other associated data such as sea surface 

 temperature or other nearby XBT observations. Con- 

 sequently a vertical section plot may have one or two 

 missing observations, resulting from the deletion of inac- 

 curate subsurface data. 



The fourth year of operation of the NMFS/MARAD 

 Ship of Opportunity Program (SOOP) was enhanced by 

 the inclusion of Coast Guard cutters as ships of oppor- 

 tunity. The Coast Guard cutters that occupy Ocean 

 Weather Station HOTEL (OWSH) (lat. 37°N, long. 

 71°W) began taking hourly XBT observations between 

 Norfolk, Va., and OWSH in August. This transect was 

 occupied monthly while OWSH was being maintained, 

 usually from August through April. We plan to resume 

 this section when OWSH is again occupied. 



Approximately 225 XBT drops and associated surface 

 data are not included because the observations were 

 much too widely separated in time and space to be useful 

 in the analysis. All data collected were archived by the 

 NODC and are available to interested persons through 

 the NODC, Washington, D.C. 20235. 



