Global Analysis of Surface Ocean CO2 Fugacity and Air‐Sea Fluxes With Low Latency.

The Surface Ocean CO2 Atlas (SOCAT) of CO2 fugacity (fCO2) observations is a key resource supporting annual assessments of CO2 uptake by the ocean and its side effects on the marine ecosystem. SOCAT data are usually released with a lag of up to 1.5 years which hampers timely quantification of recent variations of carbon fluxes between the Earth System components, not only with the ocean. This study uses a statistical ensemble approach to analyze fCO2 with a latency of one month only based on the previous SOCAT release and a series of predictors. Results indicate a modest degradation in a retrospective prediction test for 2021–2022. The generated fCO2 and fluxes for January–August 2023 show a progressive reduction in the Equatorial Pacific source following the La Niña retreat. A breaking‐record decrease in the northeastern Atlantic CO2 sink has been diagnosed on account of the marine heatwave event in June 2023. Plain Language Summary: There is a growing need to monitor carbon emissions and removals over the globe in near real time in order to correctly interpret changes in CO2 concentrations as they unfold. For the oceans, the best information comes from measurements of the surface ocean CO2 fugacity (fCO2) by the international marine carbon research community. So far, this data is mostly available 6 to 18 months behind real time after collection, qualification, harmonization, and processing. Here, we show that a set of biological, chemical, and physical predictors available in near real time, allows the information contained in the "old" fCO2 measurements to be transferred over time. Based on a statistical technique, we combine all these data sources to estimate global monthly maps of fCO2 and of CO2 fluxes at the air‐sea interface within one month behind real time and with good accuracy. Key Points: We demonstrate the capacity of statistical models to generate global maps of fCO2 and air‐sea flux with a latency reduced to one monthA decrease in the CO2 source for January to August 2023 diagnosed in the tropical Pacific coheres with the retreat of the La Niña eventAn unusual northeastern Atlantic sink reduction diagnosed for June 2023 is linked to record heat and exceptionally low winds [ABSTRACT FROM AUTHOR]