Purpose. The study is purposed at assessing and analyzing spatial variability and seasonal dynamics of the carbonate system parameters in the fjords of Western Spitsbergen based on the results of field research in the spring (April) and summer (August) seasons, 2023.

Methods and Results. The physical and chemical parameters of water, such as total alkalinity, pH and nutrient contents were studied. The samples were analyzed in the chemical analytical laboratory of the Russian Scientific Center at Spitsbergen (RSCS). The pH was measured using a Mettler Tolledo Seven Compact S220 laboratory pH-meter, and total alkalinity -- by direct titration of a seawater sample with a 0.02 hydrochloric acid (the equivalence point was determined visually). The concentrations of phosphates and silicates, as well as chlorophyll a were measured by standard spectrometric methods. The carbonate system parameters and CO₂ flux direction and speed were calculated using the Program Developed for CO₂ System Calculations. The revealed seasonal dynamics and variability of the carbonate system parameters are closely related to the atmospheric conditions, water mass seasonal variability and intensity of bioproductivity. The estimates of carbon dioxide flux obtained using the data for August 2023 allow to conclude that during this period CO₂ is absorbed in Grønfjorden (−1.52 … −4.76 mmol m⁻²·day⁻¹) and Isfjorden (−0.12 … −1.0 mmol m⁻²·day⁻¹), whereas in Billefjorden a local area with positively directed CO₂ flux (1.2–2.6 mmol m⁻²·day⁻¹) was discovered.

Conclusions. The studies carried out in the fjords have resulted in revealing seasonal fluctuations in the carbonate system parameters and the carbon dioxide fluxes similar to other inner fjords of Spitsbergen. The obtained results highlight the importance of the carbonate system parameters in understanding the biogeochemical balance and the state of marine ecosystems in the context of climate change.