Modeling the impacts of cave ventilation and CO2 dynamics on speleogenesis

Approximately 10 years worth of field observations of dissolved and gaseous CO₂ within caves and karst springs across a variety of settings suggest that CO₂ dynamics provide a first-order control on both the spatial and temporal variability in dissolution rates within karst systems. Three primary effects emerge from the field studies: 1) Changes in stream slope, sediment characteristics, and resulting CO₂ production and exchange can drive longitudinal variability in dissolution rates along cave streams; 2) Cave airflow patterns, and resulting cave gaseous CO₂ concentrations, can be the primary control on the variability of in-stream dissolution rates over storm to seasonal timescales; 3) The maturation of karst systems and resulting increases of permeability within the vadose zone can increase ventilation of the subsurface, reduce the PCO₂ of water flowing through cave passages, and ultimately reduce dissolution rates within these passages. While these effects are evident from the field data, it is difficult to quantify the long-term impacts of these effects on the evolution of karst systems using field data alone. The processes of CO₂ production, cave ventilation, and CO₂ exchange between gas and liquid phases have not been included in previous numerical models of speleogenesis. Here we extend existing models of speleogenesis to incorporate a suite of processes that are relevant for simulating physically realistic CO₂ dynamics. We use this new model to explore the impacts of ventilation and CO₂ exchange over timescales relevant for the evolution of karst aquifers.