Carbon dioxide is one of the climate-forming substances; its entry into the atmosphere and further redistribution in the waters of the World Ocean play a significant role in the formation of the climate on the Earth and affect water characteristics. The study of inland seas, such as the Black Sea, makes it possible to study the influence of atmospheric CO₂ on water characteristics and to assess the contribution of regional ecosystems to the total CO₂ budget of the World Ocean waters. The paper provides quantitative estimates of the sea-air CO₂ flux, analyses its direction, and identifies the factors determining the CO₂ flux in the northeastern part of the Black Sea during the cold period. The data obtained during the expeditionary studies on board the R/V Professor Vodyanitsky in December 2022 were used for the analysis. The value of the carbon dioxide flux at the water-atmosphere interface was calculated taking into account wind speed and the pCO₂ gradient between the sea surface and the near sea surface atmosphere. According to the direct determination of pCO₂, the CO₂ flux values in December 2022 varied widely from -0.05 to -8.74 mmol·m⁻²·day⁻¹, the average value being -2.11±1.79 mmol·m⁻²·day⁻¹. It was established that during the cold season, the CO₂ was directed from the atmosphere to the sea surface. Thus, the waters of the Crimean coast serve as a stock of atmospheric CO₂. Local flux minima were observed in the southeastern part of the Crimean coast. When analyzing the correlation of the CO₂ flux with temperature, wind speed and ΔpCO₂, the strongest relationship was found with wind speed (-0.93), while the weakest one was with ΔpCO₂ (0.22). Therefore, the intensity of the sea-air CO₂ flux was determined by wind speed, while the direction of the flux was determined by ΔpCO₂. The temperature contribution manifested as change in the concentration of CO₂ in the water column.