Cave Ventilation and Dripwater Geochemistry: Modern Time Series Speleothem Paleoproxy Calibration

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The research team aims to study cave aerodynamics and dripwater chemistry to better understand how speleothems grow and how they incorporate paleoclimate signals into their calcite bands. This research complements an ongoing monitoring campaign established in Hollow Ridge Cave (HRC), Marianna, Florida. As part of ongoing efforts, the researchers have been able to establish a simple model for cave air exchange with outside air and, thus, the rate of carbon dioxide ventilation in and out of this cave as it breathes. This has been achieved by continuously measuring 222Rn (radon), carbon dioxide, temperature, barometric pressure, relative humidity (in situ air density), rainfall (cave drip rates), wind speed and direction (cave air flow), and solar irradiance.By expanding this array of in situ cave monitoring instruments to determine high resolution 3D and temporal air and water (drip) flow and chemistry through the cave (hydraulics), the researchers aim to provide a better understanding of the processes and environmental controls on using speleothems as paleoclimate proxies. In effect, the research team will calibrate the isotopic and chemical signals preserved in ?modern? calcite precipitated in a well-understood cave with the isotopic and chemical signatures in the cave air and drip.The researchers plan several specific experiments that include: (1) deploying a dense array of micro-scale temperature and air flow sensors to map ventilation; (2) measuring existing active stalagmites for growth rates and isotopic and trace element compositions; (3) analyzing rainwater and drip water for chemistry and isotopic composition (time series); (4) running benthic flux experiments to establish rates of 222Rn emanation into the cave from limestone walls and drips; (5) establishing internal exchangeable cave air volume; (6) dye-chasers to estimate the epikarst volume and flow patterns; and (7) hydraulic groundwater gradients around the cave.The primary broader impacts involve the potential for improved understanding of the limitations and utility of a widely used climate proxy and the support of undergraduate and graduate students.