75 m; instead they included a 1,250 m sample. 

 For deep casts, the desired depths were 2,000 m, 

 2,500 m, 3,000 m, 3,500 m, 4,000 m, and 150 

 m and 50 m off the bottom. Attempts were made 

 to complete at least one deep cast during each 

 patrol. 



A pair of protected deep sea reversing ther- 

 mometers was fitted on each Nansen bottle. Four 

 or five bottles at 200 m and below were each 

 fitted with an unprotected thermometer for the 

 thermometric determination of the sampling 

 depths. Field observations of temperature were 

 transmitted via radioteletype to the Coast Guard 

 Oceanographic Unit for real time data processing 

 and quality control. The reductions to in situ 

 temperatures were accomplished with the use of 

 a Digital Equipment Corporation PDP-5 com- 

 puter. 



Salinity samples were drawn from each Nansen 

 bottle, and salinity values were determined at 

 sea using an inductive salinometer. Duplicate 

 samples were drawn from the top and bottom 

 bottles of each cast and were analyzed by the 

 Oceanographic Unit for quality control. 



Processed temperature and salinity data for 



each cruise were submitted to the National 

 Oceanographic Data Center (NODC), Washing- 

 ton, D.C. The interpolated temperatures, salini- 

 ties, sigma-t values, geopotential anomalies, and 

 sound velocities for the standard depths were 

 computed by NODC and are listed in Tables I 

 through XIII of Appendix A. 



ANALYSIS OF DATA 



OS DELTA provides an opportunity to investi- 

 gate the surface (600 m) effects of a shifting 

 current regime which separates the Subarctic 

 Water mass to the north and the North Atlantic 

 Central Water mass to the south. Prior to discus- 

 sion of this system, a brief description of the 

 influencing current and water masses is provided. 



Northern Gulf Stream Extension 



Just off the Tail of the Banks (43°N, 51°W) 

 the eastward flowing Gulf Stream develops large 

 fluctuations in stream position as it migrates 

 northeastward. Iselin (1936) defined these fluctu- 

 ations as an extension of the Gulf Stream called 



