In this article, we present the first climatological map of air–sea CO₂ flux over the Baltic Sea based on remote sensing data: estimates of pCO₂ derived from satellite imaging using self-organizing map classifications along with class-specific linear regressions (SOMLO methodology) and remotely sensed wind estimates. The estimates have a spatial resolution of 4 km both in latitude and longitude and a monthly temporal resolution from 1998 to 2011. The CO₂ fluxes are estimated using two types of wind products, i.e. reanalysis winds and satellite wind products, the higher-resolution wind product generally leading to higher-amplitude flux estimations.

Furthermore, the CO₂ fluxes were also estimated using two methods: the method of Wanninkhof et al. (2013) and the method of Rutgersson and Smedman (2009). The seasonal variation in fluxes reflects the seasonal variation in pCO₂ unvaryingly over the whole Baltic Sea, with high winter CO₂ emissions and high pCO₂ uptakes. All basins act as a source for the atmosphere, with a higher degree of emission in the southern regions (mean source of 1.6 mmol m⁻² d⁻¹ for the South Basin and 0.9 for the Central Basin) than in the northern regions (mean source of 0.1 mmol m⁻² d⁻¹) and the coastal areas act as a larger sink (annual uptake of −4.2 mmol m⁻² d⁻¹) than does the open sea (−4 mmol m⁻² d⁻¹). In its entirety, the Baltic Sea acts as a small source of 1.2 mmol m⁻² d⁻¹ on average and this annual uptake has increased from 1998 to 2012.