D379 discrete salinity sampling document
Originator's protocol for data acquisition and analysis
The following information contains extracts from the D379 cruise report.
Discrete salinity samples were collected on the majority of CTD casts performed during the cruise. One sample was taken from each of the CTD Niskin bottles selected for analysis. Replicate samples from the same Niskin bottle were occasionally taken to monitor analytical quality. In addition, discrete samples were also drawn from the ship's non-toxic underway supply at approximately four hour intervals.
Sample collection was carried out carefully using clean glass sample bottles. Each of these was rinsed three times in the sample stream prior to being filled to below the neck of the bottle. After wiping residual droplets from the neck with clean tissue, a clean plastic stopper was placed in the top and the bottle cap fitted. Samples were taken to the constant temperature laboratory to stabilise prior to analysis.
The samples were analysed onboard using a Guildline Autosal 8400B (s/n 60839) salinometer in the constant temperature laboratory (kept at 24 °C). CTD bottle salinities were ultimately used by the data originator to calibrate both CTD conductivity sensors. Discrete underway salinity samples were used to calibrate the thermosalinograph conductivity sensor data stream.
BODC data processing procedures
The salinity data were supplied to BODC in Microsoft Excel format. Salinity values were extracted from the file and loaded into BODC's Oracle relational database. Replicate data were averaged (and population standard deviations calculated) prior to loading, where necessary. Data that were considered unrealistic were flagged suspect. Metadata collected from the various data files were favoured by BODC over the metadata recorded in the cruise report logs present in the D379 cruise report.
Content of data series
| Originator's Parameter | Unit | Description | BODC Parameter code | BODC Unit | Comments |
|---|---|---|---|---|---|
| Discrete CTD/underway salinity | - | Practical salinity of the water body by bench salinometer and computation using UNESCO 1983 algorithm | PSALBSTX | - | N/A |
| Standard deviation for CTD bottle salinity | - | Practical salinity standard deviation of the water body by bench salinometer | PSSDBSTX | - | Calculated for instances where duplicate CTD salinity samples were provided |
Data quality report
No problems reported and no significant issues encountered during BODC data banking procedures.
References cited
Griffiths C. R. et al. , (2012). RRS Discovery Cruise D379, 31 Jul 2012 - 17 Aug 2012. Southampton to Reykjavic - the Extended Ellett Line. Scottish Association for Marine Science, 184pp. (Scottish Marine Institute, Oban.)
Available - Cruise D379 Internal Report
