Metrological traceability path for marine pCO2 measurement results

Despite the increasing availability of sensors for gathering data on the partial pressure of CO2 (pCO2) in the waters of the world's seas and oceans, there is a growing awareness within the scientific community of the pressing need for very high quality measurements of the variable to help monitor the Ocean Acidification threat and, more generally, the effectiveness of overall global CO2 emission mitigation strategies. This is because discriminating observed variations ascribable to long-term trends from the ones due to natural fluctuations and meeting established criteria to reach the “Climate goal” for marine carbonate system research and monitoring require extremely accurate and traceable pCO2 measurements to be useable. Here, we present some details on work being done to expand the use of reference-grade CO2 gas mixtures to help calibrate and/or assess the performances of marine sensors employed for measuring seawater pCO2.