Opposite to atmospheric CO
2 concentrations, which reach a minimum during the vegetation season (e.g., June–August in the Northern Hemisphere), soil CO
2 reaches a maximum in the same period due to the root respiration. In karst areas, characterized by high rock porosity,
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Opposite to atmospheric CO
2 concentrations, which reach a minimum during the vegetation season (e.g., June–August in the Northern Hemisphere), soil CO
2 reaches a maximum in the same period due to the root respiration. In karst areas, characterized by high rock porosity, this excess CO
2 seeps inside caves, locally increasing pCO
2 values above 1%. To better understand the role of karst areas in the carbon cycle, it is essential to understand the mechanisms of CO
2 dynamics in such regions. In this study, we present and discuss the spatial and temporal variability of air temperature and CO
2 concentrations in Samograd Cave, Croatia, based on three years of monthly spot measurements. The cave consists of a single descending passage, resulting in a characteristic bimodal climate, with stable conditions during summer (i.e., stagnant air inside the cave) and a strong convective cell bringing in cold air during winter. This bimodality is reflected in both CO
2 concentrations and air temperatures. In summer, the exchange of air through the cave’s main entrance is negligible, allowing the temperature and CO
2 concentration to equilibrate with the surrounding rocks, resulting in high in-cave CO
2 concentrations, sourced from enhanced root respiration. During cold periods, CO
2 concentrations are low due to frequent intrusions of fresh external air, which effectively flush out CO
2 from the cave. Both parameters show distinct spatial variability, highlighting the role of cave morphology in their dynamics. The CO
2 concentrations and temperatures have increased over the observation period, in line with external changes. Our results highlight the role of caves in transferring large amounts of CO
2 from soil to the atmosphere via caves, a process that could have a large impact on the global atmospheric CO
2 budget, and thus, call for a more in-depth study of these mechanisms.
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