A new publication with acknowledgement to OC4C has been published in Nature Communications.
The paper is highly relevant to Option 1 of our project. Among the named scientists involved are three from our OC4C project Mingxi Yang, Thomas Bell, and David Woolf. The findings suggest that bubble-induced asymmetry (favoring gas invasion over evasion) may increase data-based estimates of oceanic CO2 fluxes by approximately 0.3–0.4 Pg C yr-1.
The image above shows the impact of asymmetric transfer on the sea-air CO2 flux estimate (∆Flux). A Map of ∆Flux; B 1°-latitude mean of ∆Flux and ERA5 wind speed; C Temporal trend in annual mean ∆Flux; D Seasonal variations of ∆Flux in northern (green) and southern (purple) hemispheres (1–12 corresponding to January-December). The results shown here represent the ensemble mean ∆Flux estimated from two different ∆s parameterisations (Eqs. 5 and 6). The ∆Flux shown in (A, B, and D) is averaged from 1991 to 2020. A negative ∆Flux means enhanced ocean CO2 uptake.
Abstract: Sea-air carbon dioxide (CO2) flux is typically estimated from the product of the gas transfer velocity (K) and the CO2 fugacity difference between the ocean surface and atmosphere. Total gas exchange comprises interfacial transfer across the unbroken surface and bubble-mediated transfer from wave breaking. While interfacial transfer is symmetric for invasion and evasion, bubble-mediated transfer theoretically favours invasion due to hydrostatic pressure, though field evidence has been lacking. Here we provide direct field evidence of this asymmetry and develop an asymmetric flux equation. Applying the asymmetric equation reduces bias in K, and increases global oceanic CO2 uptake by 0.3-0.4 Pg C yr-1 (~15% on average from 1991 to 2020) relative to conventional estimates. Further evasion data are needed to better quantify the asymmetry factor. Our study suggests that the ocean may have absorbed more CO2 than previously thought, and the asymmetric equation should be used for future CO2 flux assessments.