Expendable Bathythermograph Observations from 

 the NMFS/MARAD Ship of Opportunity Program 



for 1973 



STEVEN K.COOK 1 



ABSTRACT 



Results of the third year of operation of the NMFS/MARAD Ship of Opportunity Program are 

 presented in the form of vertical distributions of sea surface temperature and salinity. Included are 

 descriptive analyses of the most dynamic transects showing the Caribbean/Yucatan/Loop/Florida Current 

 regimes, the Gulf Stream, associated eddies, and the bottom cell of cold water off the U.S. east coast. 

 Operational and data management procedures also are discussed. 



INTRODUCTION 



In midyear of 1970 a cooperative expendable bathyther- 

 mograph (XBT) program was initiated between the National 

 Marine Fisheries Service (NMFS) and the Maritime 

 Administration (MARAD) of the U.S. Department of 

 Commerce. The program, conducted in support of the 

 Marine Resources Monitoring Assessment and Prediction 

 Program of NMFS, involved the use of Maritime Cadets 

 from 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 eastern tropical Atlantic, 

 Caribbean Sea, Gulf of Mexico, and western North Atlantic, 

 utilizing merchant ships as relatively inexpensive platforms 

 for the collection of data. The program objective has been 

 modified recently to eliminate the tropical Atlantic and most 

 of the Caribbean, concentrating on the western North 

 Atlantic and Gulf of Mexico. 



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 interest were the 

 Yucatan Current, Gulf 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 



Subsurface temperature data were obtained by use of 

 Sippican XBT systems. At the same time surface water 

 samples were collected with bucket thermometer units for 

 later analysis to determine salinity. The surface water 

 samples were analyzed on shore using a Beckman inductive 

 salinometer calibrated with standard (Copenhagen) water at 

 least once every 30 samples. The XBT traces were 



'Atlantic Environmental Group, National Marine Fisheries Service, 

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



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 essentially camera ready and needed little hand 

 correcting. The few corrections necessary were made by 

 discarding anomalous XBT observations that could not be 

 supported by other associated data such as sea surface 

 temperature or other nearby XBT observations. Conse- 

 quently a vertical section plot may have one or two missing 

 observations resulting from the deletion of inaccurate 

 subsurface data. 



All data collected were archived by the NODC and are 

 available to interested persons through the NODC, 

 Washington, D.C. 20235. Approximately 146 additional XBT 

 observations and associated surface data were archived at 

 the NODC, but not discussed in this report. The 

 observations were too scattered in time and space to be 

 formed into meaningful transects. 



Further details concerning the acquisition or processing 

 of data from the cruises considered here can be obtained 

 from the author. 



DISCUSSION 



This third year of operation of the NMFS/MARAD Ship 

 of Opportunity Program (SOOP) was highlighted by a major 

 program change. Instead of transoceanic XBT transects 

 consisting of 4-6 observations per day, a more intense 

 coverage over a smaller geographical area (hourly observa- 

 tions for the first 24 h after leaving port and the last 24 h 

 before reentering port) was initiated. This has made 

 possible the monitoring of portions of the Shelf Water-Slope 

 Water front, North Wall of the Gulf Stream, Gulf Loop 

 Current, and associated eddies. 



The SOOP effort for 1973 consisted of a total of 15 

 cruises, 7 sailing from New Orleans and 8 from New York. 

 Twenty-three transects of subsurface temperature data and 

 associated surface data were obtained. A total of 357 XBT's 

 were launched; of these, 211 (60%) were considered of 

 sufficient quality to be incorporated into the transects 

 presented in this report. Participation of midshipmen as 

 data collectors does not allow for year-round coverage, 



