PROCEDURES 



Oceanographic Sampling 



Temperature and Salinity 



At each station an STD (Salinity-Tempera- 

 ture-Depth system) cast was taken to the 

 bottom or to the maximum STD operating 

 depth of 1,500 meters, yielding a continuous 

 trace of temperature and salinity as a function 

 of depth. In shoal waters where there was 

 danger of losing the STD "fish" on the bottom, 

 or when the seas were too rough to permit safe 

 shipboard handling of the STD, a standard 

 Nansen cast with reversing thermometers was 

 taken to determine the temperature and sal- 

 inity profiles (computation of salinity from 

 conductivity based on tables published by 

 UNESCO/NIO, 1966). A Nansen cast to col- 

 lect water samples at standard depths of 1, 10, 

 20, 30, 40, 50, 75, 100, 200, and 250 meters (as 

 depths permited) was also taken for each sta- 

 tion. Midway between stations expendable 

 bathythermograph (XBT) casts were made. 

 The positions at which the XBT's were dropped 

 are indicated on the cruise tracks for Septem- 

 ber and December (figs. 1 and 2). On the re- 

 turn leg of the December cruise, XBT's were 

 dropped every 3 hours. 



Chemical Analyses 



Water samples were analyzed for dissolved 

 oxygen using the modified Winkler method 

 (Carpenter, 1965). Aliquots of 125 ml of sea 

 water were taken from water samples collected 

 at the standard depths down to 100 meters for 

 a determination of the cholorophyll content. 

 The aliquots were filtered and the filters were 

 frozen and stored in the ship's freezer. The 

 filters were later analyzed ashore at the BCF 

 Biological Laboratory, Woods Hole, Mass. 

 Chlorophyll (total pigment) determinations 

 were made according to the method of Yentsch 

 and Menzel (1963) as modified by Yentsch 

 (1965). 

 Bathymetry and Meteorology 



A continuous sonic sounding program was 

 carried out by bridge personnel, and LOR AN 

 C was used for navigation. Meteorological and 

 sea surface conditions were likewise recorded 

 at each station by bridge personnel. These data 

 included cloud type and coverage, wind speed 



and direction, air temperature, barometric 

 pressure, wave height, wave direction, and 

 wave period. The weather data were combined 

 with the water temperature data and sent by 

 radio message to the Fleet Numerical Weather 

 Facility, Monterey, Calif., after completion of 

 each station deeper than 100 fathoms. 



Operational Summary 



September December 

 Hydrographic stations 



occupied 61 34 



STD casts 58 32 



XBT casts 34 35 



Nansen casts 48 31 



Dissolved oxygen analyses 350 220 

 Chlorophyll (total pigment) 



analyses 286 183 



Quality Control 



Every 24 hours a complete Nansen cast, with 

 reversing thermometers, was made in conjunc- 

 tion with an STD cast. Water samples were 

 drawn for a determination of salinity by ship- 

 board salinometers. The control salinities and 

 the corrected thermometer temperatures were 

 then compared with the STD readings at cor- 

 responding depths. Attempts were made to 

 take the quality control Nansen casts at the 

 deeper stations in order to obtain comparisons 

 over the widest range possible. The disad- 

 vantage of this method is that the STD and 

 Nansen casts cannot be made simultaneously. 

 Changes in the water column between casts and 

 error in determining sampling depth limit the 

 value of quality control data acquired by this 

 technique in the thermocline and halocline. A 

 Nansen bottle was hung directly above the STD 

 during the December cruise, and data from this 

 single bottle were used on each STD cast, along 

 with the 24. hour quality control Nansen cast 

 data, for calibration. 



All STD traces were read twice by different 

 personnel to reduce the possibility of reading 

 errors. Sigma-t values were determined by 

 computer to indicate the existence of density 

 inversions. The salinity and temperature data 

 which produced these inversions were then re- 

 checked for reading errors. When the existence 

 of density inversions could not be resolved, the 

 data were marked as questionable. The Coast 

 Guard Field Party maintained a time adjusted 



