Quantifying observational errors in Biogeochemical‐Argo oxygen, nitrate, and chlorophyll a concentrations

Biogeochemical (BGC)‐Argo floats observations are becoming a major data source for assimilation into and constraining of ocean biogeochemical models. An important prerequisite for a successful synthesis between models and observations is the characterization of the observational errors in BGC‐Argo float data. The root‐mean‐square error and multiplicative and additive biases in quality‐controlled data sets of oxygen, nitrate, and chlorophyll a concentrations collected with 17 BGC‐Argo floats in the Mediterranean Sea between 2013 and 2017 are assessed using the triple collocation analysis. The analysis suggests that BGC‐Argo float oxygen, nitrate and chlorophyll a concentrations data have an additive bias of 2.9 ± 5.5 μmol/kg, 0.46 ± 0.07 μmol/kg, and −0.06 ± 0.02 mg/m3, respectively. The root‐mean‐square error is evaluated at 5.1 ± 0.8 μmol/kg, 0.25 ± 0.07 μmol/kg, and 0.03 ± 0.01 mg/m3. Additional studies should determine whether these values are applicable to the global ocean.