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Highlights

  • Karst ventilation shows strong seasonal variability at massif scale
  • Summer airflow is dominated by chimney-effect ventilation
  • Winter ventilation is consistent with multiple driving mechanisms
  • Cold-air pooling modifies airflow in dolines and poljes
  • Ventilation may contribute to heat transfer in the karst vadose zone

Abstract

Karst systems are heterogeneous environments in which water flow is commonly assumed to control subsurface thermal dynamics. However, the role of air circulation at the system scale remains poorly constrained. This study presents a characterization of the thermal expression of ventilation processes in a western Betic Range (southern Spain) karst massif, based on the continuous monitoring of air temperature in multiple conduits distributed along an altitudinal gradient, combined with the analysis of external atmospheric conditions. Results show that ventilation is strongly seasonal and controlled by the interaction between thermal gradients, transient atmospheric variations and system geometry. The observations reveal recurrent spatial and seasonal patterns of ventilation across the monitored karst-atmosphere interfaces. These patterns are consistent with ventilation mechanisms previously described. During summer, ventilation appears to be dominated by the chimney effect, suggesting a coherent airflow pattern with air inflow in upper sectors and persistent outflow through low-elevation conduits. In contrast, the thermal expression of winter ventilation is weaker and more heterogeneous, with a greater influence of transient meteorological forcing and local modifications associated with cold-air pooling in topographic depressions, which may modify local airflow. The results also highlight the influence of conduit geometry and topographic setting on karst ventilation. Large conduits favor sustained thermally driven flow, whereas smaller conduits show more transient thermal responses associated with atmospheric-pressure variations or wind conditions.  From a thermal perspective, the discrepancy between expected and observed spring temperatures is consistent with an additional contribution from air-mediated heat transport beyond that accounted for by the simplified water-based thermal budget. Thus, the proposed ventilation model suggests that air circulation may contribute to the thermal regime of the massif potentially comparable to that of groundwater. These results highlight ventilation as a potentially important component of heat transfer within the karst vadose zone, with potential implications for hydrogeochemical processes.

DOI

https://doi.org/10.5038/1827-806X.ijs2615

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

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