Scaling and intermittent properties of atmospheric and oceanic turbulent pCO2 time series and their difference

The oceans interact and exchange CO₂ with the atmosphere through different processes that form the biological and physical pumps. The atmospheric and oceanic partial pressures of CO₂ are therefore chemical tracers impacted by numerous forcing processes, including turbulence. Turbulence thus has an impact on the fluctuations of pCO₂ and on their difference, the sign of which determines the direction of the air-sea flux of CO₂.

Here, we used a published database (Sutton et al., 2019) to study the scaling properties of sea temperature, sea salinity, atmospheric and oceanic pCO₂ and their difference ∆pCO₂ time series recorded at 38 locations every 3 hours. Fourier spectral analysis revealed scaling for ranges between 3 days and 3 months approximately. The statistics of spectral slopes over this scaling range has been considered. Then, empirical mode decomposition and Hilbert spectral analysis were used to study the intermittency properties of the time series of 3 buoys having a large enough data points. For all three locations the intermittent multifractal properties of pCO₂ were considered. Some main parameters were extracted assuming a lognormal multifractal model.