Paper No. 335-3
Presentation Time: 2:05 PM
INTERACTIONS AMONG CAVE AIRFLOW, CARBON DIOXIDE, AND DISSOLUTION RATES WITHIN KARST CONDUITS
Models of both speleogenesis and carbon dynamics within karst systems are often generalized to large spatial and temporal scales that obscure short-term variability. The controls on short-term and small-scale variability in dissolution rates within natural karst settings are not well-constrained, even though such variations may ultimately control the long-term and large-scale rates. Understanding spatial and temporal variability in dissolution rates is crucial to quantifying the role of karst within Earth's carbon cycle. Here we use a combination of theoretical and observational studies to demonstrate that buoyantly driven airflow within karst systems can be a primary driver of short- and long-term carbon dioxide (CO2) dynamics. Consequently, airflow also provides a strong control on variations in calcite dissolution rates within karst conduits. We used a recently developed sensor technology, encasing CO2 gas sensors within a waterproof breathable membrane, to obtain high temporal resolution measurements of dissolved CO2. These sensors were deployed at two karst springs and one cave stream, along with other water quality sensors, to obtain multi-year records of carbon dioxide and dissolution rate dynamics. Airflow velocity and other meteorological parameters were also monitored at the in-cave site. The three sites illustrate the influence of air-water CO2 exchange on both short-term variability and long-term averages of calcite dissolution rates. Theoretical considerations suggest that, in many cases, such effects should also be active within fractures and small conduits within the karst vadose zone. Therefore, buoyantly-driven airflow is an important control on the carbon cycle within karst systems and subsequently on the spatial and temporal patterns of karst system evolution. This research highlights the need for a better understanding of gas dynamics within karst systems to enable quantification of the role of karst within the global carbon cycle.