*** Documentation for the CTD data collected on RRS John Biscoe Cruise  10                                                          
(11 Dec 1989 - 21 Mar 1990)  by the British Antarctic  Survey,  Cambridge,                                                          
U.K., under the direction of J. Priddle ***                                                                                         
                                                                                                                                    
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      *  WARNING: Salinity data are highly suspect, see note below  *                                                               
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DATA COLLECTION                                                                                                                     
The   instrument  used was a Neil Brown Instruments System Mark IIIB  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  accuracy  of  the temperature  data  is  thought  to  be                                                          
+/-0.01degC.                                                                                                                        
                                                                                                                                    
DATA PROCESSING                                                                                                                     
Calibrations  were applied and the data despiked by rejecting data  values                                                          
outside  of predetermined tolerances.  Data values were then  averaged  to                                                          
provide data at 1 decibar intervals.                                                                                                
                                                                                                                                    
** WARNING **                                                                                                                       
The  data  are derived from instruments which were  laboratory  calibrated                                                          
(for  pressure  and temperature anyway), but not  finally  adjusted  using                                                          
reversing thermometers or salinity derived from in situ samples.  The data                                                          
required  for  this final adjustment are either missing or of too  poor  a                                                          
quality for calibration. Therefore these CTD data are of varying quality -                                                          
the  temperature  data are reasonable,  but the salinity data  are  HIGHLY                                                          
SUSPECT and should not be used for detailed physical studies. The salinity                                                          
data  are  probably  just  about good enough for  setting  the  scene  for                                                          
biological  studies  since they can be used to show  relative  changes  in                                                          
space  or  time  but are not accurate enough  to  show  absolute  salinity                                                          
levels.                                                                                                                             
                                                                                                                                    
The  deep water salinity data from the CTD have been compared  with  other                                                          
measurements made in this region and also with the Levitus Atlas. They are                                                          
approximately  0.16 ppt  lower  than data  collected  on  various  cruises                                                          
including Discovery II (1929-31) and about 0.17 ppt lower than the Levitus                                                          
Atlas salinities.                                                                                                                   
                                                                                                                                    
References:                                                                                                                         
Levitus,  S.  1982  Climatological Atlas of the  World  Ocean.  NOAA  Pro-                                                          
fessional Paper No. 13. US Government Printing Office. 173pp                                                                        
