CO2 Flux on the Black Sea Surface according to Data of 2015–2024

The intra-annual course of CO2 flux at the boundary with the atmosphere for the northern part of the Black Sea is studied on the basis of direct measurements of CO2 concentration. The analysis of seasonal variability showed a significant flux dynamics: its values calculated from cruise data ranged from –17.7 to 14.3 mmol m‒2 day‒1 (the negative and positive values indicate the atmosphere-to-water and water-to-atmosphere CO2 flux, respectively). The intensity of the CO2 flux on the sea surface largely depends on regional hydrometeorological conditions (a sea surface temperature and a wind speed), as well as a pCO2 gradient between the sea surface and the atmosphere. Based on the field pCO2 data for 2015–2024 and the average monthly climate wind speed and sea surface temperature, the average annual value of the CO2 flux (–1.20 mmol m‒2 day‒1) was calculated, i.e., the study area absorb ~2.30 Mt CO2 annually, while the waters of the Black Sea absorb at least 8.03 Mt CO2.