A total of 78 bottle salinity samples were taken from a SeaBird SBE45 thermosalinograph (S/N 4524698-0016) non-toxic supply (depth of 6 m) approximately every 4 hours during the cruise. The tap supplying the underway water was open constantly and the flow rate was monitored and logged every 4 hours as part of the underway data logging procedure. All samples were taken using 200 ml glass sample bottles with plastic lids in cases of 24 bottles. Bottles were filled in order to leave minimal air for evaporation to occur, whilst leaving enough air to allow for adequate mixing of the sample before sampling to counteract any stratification which may have developed. The bottle necks and lids were dried thoroughly before plastic caps and placed inside the bottle necks immediately after sampling to seal the air within the bottles. The sample bottle was filled and emptied 3 times to ensure minimum contamination, before being filled. Once a case of sample bottles was full, it was transferred to the temperature controlled laboratory, where it remained for a minimum of 24 hours before being sampled.
Salinity measurements were taken using a Guildline AutoSal Salinometer model 8400B, S/N 68959. At the beginning of the cruise and at the beginning and end of each sampling run, the instrument was standardised using a bottle of IAPSO Standard Seawater, batch P151, conductivity ratio K15 = 0.99997, provided by OSIL. The temperature of the water bath in the salinometer was kept at 20°C throughout the cruise and the salinometric analysis was carried out as per the manufacturers recommendations. Before measurements were made, the sample bottle was gently agitated by inversion 3 times to remove any stratification, and the measurement cell was filled using the peristaltic pump and flushed three times with the relevant sample in order to avoid any contamination from previous samples. The analyst ensured that no bubbles were present in the cell before measuring the sample. Three separate measurements for each sample were made which were then averaged. All recorded measurements were converted into salinity using the UNESCO algorithm for practical salinity (UNESCO, 1981).
Further details of all the originator's analysis is detailed in the cruise report page 30.
The time, bottle number, crate number and salinity data were supplied as a csv and mstar file. BODC created originator references using the crate number together with the bottle number. The latitude and longitude for each sample were determined using the underway navigation data for the corresponding times. Data were loaded into BODC's database from the csv file without any changes. Suspect data were marked with the appropriate quality control flag.
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 |
|---|---|---|---|---|---|
| bottle 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.
UNESCO, 1981. The Practical Salinity Scale 1978 and the International Equation of State of Seawater 1980. Technical Papers in Marine Science, 36.
The bottle samples were compared to the underway TSG data and were discrepancies between the values were found, the bottle values were flagged as suspect. This affected 23 samples mostly between the 16th and 19th April, none of these values were used for the underway salinity calibration.
None (BODC assessment).