***  Documentation for the CTD data collected on RRS John Biscoe Cruise 02                                                          
(27 Feb - 15 Apr 1980) by the British Antarctic Survey,  Cambridge,  U.K.,                                                          
under the direction of R.B. Heywood.  ***                                                                                           
                                                                                                                                    
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       *  WARNING: The salinity data are of unknown quality. In  *                                                                  
          addition the salinity data are noisy (+/-0.02psu) for  *                                                                  
       *  all profiles from this cruise, particularly between    *                                                                  
       *  the surface and 500 dbar                               *                                                                  
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DATA COLLECTION                                                                                                                     
The  instrument  used was a Plessey 90/40 CTD.   Observed parameters  were                                                          
pressure,  temperature  and  conductivity.  All  sensors  were  calibrated                                                          
before  and after the cruise.   Up to 12 water bottles were mounted  on  a                                                          
Rosette  sampler  and  4 pairs of reversing  thermometers  were  attached.                                                          
Water  bottles were triggered on the downcast at 10m and at the bottom  of                                                          
the  cast,  the remainder being fired on the upcast (mainly  for  chemical                                                          
samples).  Data were collected on the downcast.                                                                                     
                                                                                                                                    
CALIBRATION                                                                                                                         
Reversing  thermometers  were calibrated at the Deacon Laboratory  of  the                                                          
Institute  of Oceanographic Sciences.   The pressure sensor  was  compared                                                          
with  a Bourdon gauge which had been calibrated at the  National  Physical                                                          
Laboratory.   The  salinities  were determined at  the  British  Antarctic                                                          
Survey  using a Guildline Salinometer.   Some time after these  data  were                                                          
supplied  to BODC the salinometer was found to have been  faulty.  However                                                          
the  original data were no longer recoverable from the  original  magnetic                                                          
tapes  to be reprocessed,  so this version of the data has been  retained.                                                          
The salinities should be treated with great caution.  The accuracy of  the                                                          
temperature data is thought to be +/-0.01deg C.                                                                                     
                                                                                                                                    
DATA PROCESSING                                                                                                                     
Calibrations  were  applied and derived  quantities were   computed   from                                                          
algorithms  published  by  Fofonoff  and Millard (1983).  Data  were  then                                                          
averaged  into  1 decibar intervals,  centred on unit  values.   BODC  has                                                          
visually inspected the data and flagged spikes in the data as appropriate.                                                          
However the salinity data from this cruise are very noisy (+/- 0.02  psu),                                                          
especially between 0 and 500 decibars.                                                                                              
                                                                                                                                    
The salinity data from the CTD have been compared with other  measurements                                                          
made in the same region and also with the Levitus Atlas. Deep water values                                                          
are within 0.01 ppt of other data, for example that collected on Discovery                                                          
II (1929-1931) and within 0.02 ppt of Levitus Atlas values.                                                                         
                                                                                                                                    
References:                                                                                                                         
Fofonoff,  N.P.  and Millard Jr., R.C. 1983 Algorithms for the computation                                                          
of  fundamental  properties  of  sea water.  UNESCO Technical   Paper   on                                                          
Marine Science 44                                                                                                                   
                                                                                                                                    
Levitus,  S.  1982  Climatological Atlas of the  World  Ocean.  NOAA  Pro-                                                          
fessional Paper No. 13. US Government Printing Office. 173pp                                                                        
