Oxygen Optode Profiles - A Closer Look on Facts and Artefacts

Oxygen optodes have over time replaced the Clark type electrode oxygen sensors in many instances. This article will look into the performance of one type of these optodes over more than ten years of intermittent use in a profiling mooring in the Baltic Sea. We take a look at the signal processing and the calibration coefficients and the long term signal drift of a JFE Alec Rinko III optode sensor that has been in water with intermissions for a total of 696 days over a span of 13.5 years, mostly in anoxic waters at a depth of around 180 to 200 m. The temporal response of the sensor is evaluated and the reconstruction of the “true” dissolved oxygen concentration from the measurements is discussed.