CTD bottle samples of salinity, dissolved oxygen and chlorophyll collected on cruise D253 along Extended Ellett Line
Originator's Protocol for Data Acquisition and Analysis
A large scale CTD survey of the Iceland Basin and Rockall Trough was carried out during this cruise along the Extended Ellett Line, comprising a total of 153 CTD casts.
Salinity samples were drawn from the Niskin bottles mounted on the CTD rosette at all depths below and including 100 m, and from the surface bottle. A duplicate sample was drawn from the deepest Niskin bottle and occasionally, on the deeper stations, the Niskin fired at 1000 meters. Samples were taken using 200 ml glass sample bottles that were rinsed three times in the sample, filled to the shoulder and sealed with a disposable plastic insert and the bottle's screw cap. The samples were then analysed with a model 8400A and a model 8400 Autosal salinometer both fitted with peristaltic pumps. Analysis techniques are fully described in Allen (2001), pages 94 to 98.
Dissolved oxygen samples were drawn from each Niskin bottle. The Winkler whole bottle titration method with aperometric endpoint detection was used with equipment supplied by Metrohm, to analyse the samples onboard. Further details on analysis technique are in Allen (2001), pages 168 to 170.
Chlorophyll-a samples were obtained from each CTD bottle by filtering 100 ml of sea water onto Whatman 25 mm GF/F filters, acetone extraction and analysis on a Turner Designs AU-10 scaling Fluorometer following the Welschmeyer (1994) protocol. Further details on analysis techniques are in Allen (2001), page 140 to 141.
References
Welschmeyer, N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnol. Oceanogr. 39, 1995-1992.
Allen, J. T. 2001. RRS Discovery cruise 253 04 May - 20 Jun 2001 . Faeroes, Iceland, Scotland Hydrographic and Environemental Survey (FISHES). Southampton Oceanography Centre Cruise Report, No 37, 206pp.
Instrumentation Description
The samples were taken with a CTD frame with 24 position rosette and 24 Niskin bottles. The salinity analysis was performed using a Guildline Autosal 8400A bench salinometer. Chlorophyll-a analysis was done using Turner Designs AU-10 scaling fluorometer.
BODC Data Processing Procedures
Data were received at BODC in the form of pstar format sample files, and various spreadsheets containing nutrient, chl-a, TDN and DOC measurements. Bottle metadata were derived from the pstar files as these recorded rosette position and pressure, whereas some spreadsheets only recorded the nominal depths of bottle firing. Having combined the two data sources, the data were loaded into the BODC database using established BODC data banking procedures.
Where no pressure or depth information could be found from any source, a small number of bottles and measurements from them were discarded.
Parameters from the originator's source files were mapped to BODC parameter codes as follows:
| Originator's Parameter | Unit | Description | BODC Parameter Code | BODC Unit | Comments |
|---|---|---|---|---|---|
| botsal | pss-78 | Salinity from bottle sample determined by bench salinometer | PSALBSTX | dimensionless | n/a |
| botoxy | µmol/l | Dissolved oxygen from bottle sample determined by Winkler titration | DOXYWITX | Micromoles per litre | n/a |
| chl | mg/m3 | Chlorophyll-a from bottle sample determined by filtration, acetone extraction and fluorometry | CPHLFLP1 | Milligrams per cubic metre | n/a |
Data Quality Report
No report provided by the originator, but information about data quality is included in Allen (2001).
Problem Report
No problem report.
