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CD176 Discrete Dissolved Oxygen Sampling Document

Originator's Protocol for Data Acquisition and Analysis

Dissolved oxygen samples were collected from multiple Niskin bottles on many of the CTD casts performed during CD176. Oxygen samples were collected before any others 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 30 minutes. 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 , (2005) 'Cruise CD176 Birkenhead to Falmouth via Rockall, Iceland and Oban', Internal Report No 248, Scottish Association for Marine Science.

Available - Cruise CD176 Internal Report

BODC Data Processing Procedures

Dissolved oxygen measurements were supplied to BODC in Microsoft Excel spreadsheets. Measurements in units of µmol/l and µmol/kg were supplied. The former were chosen for entry into the BODC database, copies of the latter remaining in our secure archive system. Extracted values were loaded into BODC's ocean database under an ORACLE Relational Database Management System. Data that were considered unrealistic were flagged suspect.

Content of data series

Originator's Parameter Unit Description BODC Parameter code BODC Unit Comments
Dissolved oxygen concentration µmol/l Concentration of oxygen per unit volume of the water body by Winkler titration DOXYWITX µmol/l n/a