RRS Discovery Cruise D321B Discrete CTD Oxygen Samples
Originator's Protocol for Data Acquisition and Analysis
Discrete dissolved oxygen bottle samples were taken from two or three Niskin bottles (20 litre volumes) on each of 23 CTD casts performed during cruise D321B. This resulted in a total of 66 oxygen samples. Oxygen samples were collected first from the CTD package. Samples were drawn using a piece of rubber tubing connected to the bottom of the Niskin bottle. Sample bottles were filled, with water from the Niskin being allowed to overflow until the bottle had been flushed by approximately three times the amount of water required to fill it. Samples were immediately fixed using 1 ml of manganese chloride and 1 ml of alkaline iodide, with a further 1 ml of sulphuric acid being added after samples had been shaken and left for 2 hours. A Winkler titration technique was then performed by a Dissolved Oxygen Analyser (DOA) to produce dissolved oxygen measurements. These were used to calibrate the oxygen sensor on the CTD frame.
References Cited
Sherwin, T. A. et al, (2007) 'Cruise D321B Reykjavic to Clyde via Rockall, Scotland and the Wyville Thomson Ridge', Internal Report No 255, Scottish Association for Marine Science.
Available - Cruise D321B Internal Report
BODC Data Processing Procedures
Data were supplied to BODC as part of a bulk post-cruise archive submission. Oxygen data from both the stainless steel and titanium CTD frames were supplied within a single Excel spreadsheet. Values (and associated errors) were extracted and loaded to BODC's Oracle database. Values were mapped to standard BODC parameter codes, as recorded in the table below.
| Originator's Parameter | Originator units | Description | BODC Parameter Code | BODC units | Comments |
|---|---|---|---|---|---|
| O2 (µmol l -1 )(Winkler) | µmol l -1 | Concentration of oxygen per unit volume of the water body by Winkler titration | DOXYWITX | µmol l -1 | - |
| STDEV(Winkler) | µmol l -1 | Concentration standard deviation of oxygen per unit volume of the water body by Winkler titration | SDOXDITX | µmol l -1 | - |
