Data-based estimates of ocean carbon uptake biased high from neglect of submonthly atmospheric pressure variability

Current estimates of the global ocean carbon sink based on measurements of CO2 fugacity are inconsistent with those obtained from global ocean biogeochemistry models. Here we investigate how this gap might be partially closed by more fully accounting for submonthly variability in observation-based estimates. While these estimates compute the air-sea CO2 flux based on hourly wind speed, other variables have only monthly resolution. Thus they neglect some high-frequency variability from short-term events such as storms. To evaluate this error, we compare fluxes at different temporal resolutions between 2009 and 2018. We find that accounting for hourly variations in atmospheric pressure and daily variations in sea surface temperature decreases the global carbon uptake estimate by 5% (0.12 Pg C yr-1) which is driven by the submonthly covariance between wind speed and atmospheric pressure, particularly in the southern extratropics. This represents 25% of the average gap between observation-based and model estimates.