Integrated analysis of carbon dioxide and oxygen concentrations as a quality control of ocean float data
Yingxu Wu, Dorothée C. E. Bakker, Eric P. Achterberg, Amavi N. Silva, Daisy Pickup, Xiang Li, Sue Hartman, David Stappard, Di Qi, Toby Tyrrell
Abstract
Abstract The distributions of dissolved O 2 and CO 2 have not previously been systematically compared across the global surface ocean, despite their significance for life and climate. Here we analyze carbon dioxide and oxygen concentrations relative to saturation (equilibrium with the atmosphere) in surface waters, using two large datasets (ship-collected and float-collected data). When applied to a high-quality global ship-collected dataset, CO 2 and O 2 concentrations relative to saturation exhibit large seasonal and geographic variations. However, linear fits of CO 2 and O 2 deviations from saturation (ΔCO 2 against ΔO 2 ) yield y-intercepts close to zero, which suggests a requirement for data validity. We utilize this finding to investigate the accuracy of carbonate system data from biogeochemical-Argo floats. We find significant discrepancies in ΔCO 2 -ΔO 2 y-intercepts compared to the global reference, implying overestimations of float-based CO 2 release in the Southern Ocean. We conclude that this technique can be applied to data from autonomous platforms for quality assessment.