High-Frequency Correlations Between Winds and pCO2 Change the California Coastal Upwelling System From a CO2 Sink to a Source

Net sea-air CO₂ flux can be calculated from observations of seawater and atmosphere partial pressure of CO₂ (pCO₂) and estimates of the gas transfer velocity. Typically, these quantities are calculated at a monthly resolution, which misses potentially important high-frequency temporal variability. Here, we calculated sea-air CO₂ flux at a 3-hourly resolution using a 10-year mooring data set (2011–2020) from the central California coastal upwelling region. We identified a significant flux of CO₂ from the ocean to the atmosphere due to a positive correlation between seawater pCO₂ and wind speed at timescales of hours to days, particularly during the late spring and early summer upwelling season. Accounting for this variability changes the region from a net sink to a net source of CO₂ to the atmosphere. These findings imply that CO₂ fluxes computed from monthly-resolution data may miss important shorter-term variability that contributes to a net outgassing of CO₂ from the ocean.