Wave effect mechanisms enhancing sea–air CO₂ exchange and modulating seawater carbonate–pH adaptation in the POP2–waves coupled model

Abstract. Wave and bubble mechanisms have demonstrated their impact on sea–air CO₂ flux by enhancing gas transfer velocity (K_w) through significant wave height (H_s). Neglecting wave and bubble processes may lead to an underestimation of CO₂ flux under high 10-m wind speeds (U₁₀) in most state-of-the-art climate models. In this study, a waves module from the Princeton Ocean Model (POM) has been incorporated into the Parallel Ocean Program version 2 (POP2), referred to as POP2–waves, in the Community Earth System Model version 1.2.2 (CESM1.2.2) framework. The POP2–waves and a control run of CESM1.2.2 (B–CTL) CO₂ flux simulations are compared with the National Oceanic and Atmospheric Administration’s (NOAA) CarbonTracker, version 2022 (CT2022) data. Overall, bubbles contribute up to 41.3 % to the total sea–air CO₂ flux, consistent with recent studies, and POP2–waves exhibits a stronger CO₂ flux than B–CTL under high U₁₀. Likewise, the spatial distribution of POP2–waves CO₂ flux is broadly agrees with that of NOAA CT2022, although some discrepancies remain. Under the sea–air partial pressure differences (dpCO₂) negative feedback associated with the interaction between CO₂ fluxes and the carbonate–pH system, POP2–waves show increases of 11.8 %, 41.6 %, and 1.8 % in the CO₂ sink, source, and global average, respectively, compared to the B–CTL. The dpCO₂ (pH) exhibits the strongest positive (negative) regression coefficient with CO₂ flux across the global ocean. Additionally, K_w shows a positive (negative) regression coefficient with CO₂ flux in source (sink) regions, while SST displays the opposite pattern relative to K_w.