Karst cave, a seasonal carbon dioxide exchanger: an example of Sloup-Šošůvka Caves (Moravian Karst)

Abstract Part of the gaseous carbon dioxide (CO2) produced in karst soils / epikarst is transported into underground cavities / caves during the growing season by advective flux, diffusive flux, and flux associated with the degassing of seeping water. Accumulated CO2 is released into the outside atmosphere during the autumn-winter period through advective fluxes associated with ventilation of the cave in the upward airflow mode. The case study from the Moravian Karst (MK) showed that the net weight of CO2 released annually from the Sloup-Šošůvka caves (total volume of 131,580 m3 and a total area of 17,950 m2) into the external atmosphere was 348 kg. Extrapolating this value to the known MK caves (area about 352,080 m2) yielded the total CO2 flux of 6820 kg yr− 1. This flux is not very significant, representing only 0.024‰ of the annual soil respiration from entire MK area (about 2.81×108 kgCO2 yr− 1). Globally, reduced summer flux with intensified winter flux out of cave could contribute to seasonal fluctuations in CO2 concentration in the external atmosphere.