Macovei V. A., Lefèvre Nathalie, Diverrès Denis, Kinski N., Listing O., Voynova Y. G. (2025). At-sea intercomparison of a membrane-based pCO2 sensor and a traditional showerhead equilibrator system on a Ship-of-Opportunity. Limnology and Oceanography : Methods, [Early access], p. [13 p.]. ISSN 1541-5856.
Titre du document
At-sea intercomparison of a membrane-based pCO2 sensor and a traditional showerhead equilibrator system on a Ship-of-Opportunity
Macovei V. A., Lefèvre Nathalie, Diverrès Denis, Kinski N., Listing O., Voynova Y. G.
Source
Limnology and Oceanography : Methods, 2025,
[Early access], p. [13 p.] ISSN 1541-5856
The seawater partial pressure of carbon dioxide (pCO2) is an essential ocean variable needed to calculate air-sea gas exchange and to identify marine carbon sinks and sources. Recent technological developments support autonomous pCO2 measurements with sensors that are smaller and cheaper. In July 2021, these differences were highlighted during the Integrated Carbon Observation System-Ocean Thematic Centre laboratory intercomparison exercise. A key message from the intercomparison was the need for further field comparisons. Here we present the results from a field test of two generations of -4H-Jena HydroC CO2-FT membrane-based sensors alongside a General Oceanics equilibrator system. The intercomparisons were done onboard a ship-of-opportunity regularly traveling between Europe and South America. The first phase of the experiment took place in 2021, when the difference between the two instruments was within +/- 10 mu atm during 53% of the intercomparison time. For the second phase, improvements were made, including the addition of an automated cleaning routine for the membrane-based sensor, the installation of a new sensor prototype with the ability to measure a reference gas, and an updated data processing method. These changes improved the performance and, during the last 2023 journey, the mean difference decreased to 2.0 +/- 5.0 mu atm, and was within +/- 10 mu atm during 97% of the deployment time. This experiment revealed that with a suitable deployment approach considering biofouling and reference gas measurements, membrane-based sensors can measure seawater pCO2 within the Global Ocean Acidification Observing Network weather goal of 2.5% relative uncertainty on autonomous installations.
