Samples for salinity were taken from a Sea-Bird 32, 24-bottle rosette sampling system mounted on a lowered Sea-Bird 9/11 plus CTD. In total, 109 salinity samples were taken from the CTD niskin bottles and analysed, excluding 8 niskin bottles which failed to close properly. The samples were taken from 6 CTD casts and 2 towyo casts. Samples were collected on the last up-cast of each towyo.
The water samples from the niskin bottles were collected in 200 ml flat bottles. The samples were stored upside down at a controlled temperature (19.5 °C ± 0.5) for at least 24 hours before analysing, in order to adjust to the ambient laboratory temperature. Each sample was analysed in the laboratory using an Autosal 8400B Salinometer OSIL (serial number 65764). The conductivity cell was kept in a water bath at a constant temperature of 21.588 °C (± 0.002). For each sample, three separate readings were taken, with the conductivity cell being flushed between each reading. The data logger software (OSIL Salinometer Data Logger version 2009) acquired ten values for each reading and calculated the average of these. An average of the three individual readings was calculated to give an overall conductivity value for the sample, resulting in a single average salinity value for each bottle. Three sets of analysis were done in total which comprised of three crates (around 45 sampling bottles). At the beginning of each analysis the salinometer was calibrated using OSIL IAPSO standard seawater (batch P150). Standard water was also analysed as a normal sample at the beginning and the end of each analysis.
Further details of all the originator's analysis is detailed in the cruise report page 34.
The bottle reference number and salinity data were supplied as Excel files with further information compiled from CTD data from the Sea-Bird 911plus and the CTD logsheets. The bottle position and pressure data were retrieved from .btl files which were generated from the .conn and .ros files provided, using the 'bottle summary' module in SBEDataProcessing-Win32 software. The pressure was converted into depth using the standard UNESCO (1983) algorithm. The start and end times for each profile were gathered from the CTD logsheets and all the data were compiled and converted to an ASCII format file.
Suspect samples documented in the cruise report were flagged as such before the data were loaded into the BODC database.
The following table shows how the variable was mapped to appropriate BODC parameter code:
| Originator's Parameter | Units | Description | BODC Parameter Code | BODC Unit | Comments |
|---|---|---|---|---|---|
| Salinity | Dimensionless | Practical salinity of the bottle sample by bench salinometer and computation using UNESCO 1983 algorithm. | PSALBSTX | Dimensionless | n/a |
Fofonoff N.P. and Millard R.C., 1983. Algorithms for computation of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, 44, 53.
Two out of 109 samples have been flagged based upon the originator's comments supplied in the cruise report, which stated that the bottles did not have caps and that there were large offsets between the sample salinities and the CTD salinities. No further quality control flags were added by BODC.