Updated climatological mean delta fCO₂ and net sea–air CO₂ flux over the global open ocean regions

Abstract. The late Taro Takahashi (LDEO/Columbia University) provided the first near-global monthly air-sea CO₂ flux climatology in Takahashi et al. (1997), based on available surface water partial pressure of CO₂ measurements. This product has been a benchmark for uptake of CO₂ in the ocean. Several versions have been provided since, with improvements in procedures and large increases in observations, culminating in the authoritative assessment in Takahashi et al. (2009). Here we provide and document the last iteration using a greatly increased dataset (SOCATv2022) and determining fluxes using air-sea partial pressure differences as a climatological reference for the period 1980–2021. The resulting net flux for the open ocean region is estimated as -1.79 PgC yr^-1 which compares well with other global mean flux estimates. While global flux results are consistent, differences in regional means and seasonal amplitudes are discussed. Consistent with other studies, we find the largest differences in the data-sparse southeast Pacific and Southern Ocean.