HIGH RESOLUTION TEMPERATURE SAMPLING OF CAVE CLIMATE VARIATION AS A FUNCTION OF ALLOGENIC RECHARGE, COLDWATER CAVE, IOWA, USA

Factors affecting contemporary cave climate within a fluvio-karst cave system are air flow from open surface entrances, and allogenic recharge. Cave airflow in this setting is a function of air exchange with the surface environment predominantly driven by barometric fluctuations. Variations in cave stream temperature from allogenic recharge can also cause significant fluctuations in cave air temperature. Coldwater Cave, Iowa, is a dendritic cave system draining a 50-km² watershed shown to be recharged by a series of sinking/loosing streams, and a network of sinkholes. The cave has two spring entrances that are completely water filled and two closed man-made shafts. This hydrologically dynamic system provides a unique opportunity to study the affects of allogenic recharge on cave climate. Data loggers, recording at 10-minute intervals, were installed at six in-cave sites to measure air and stream temperatures, and at the two springs to measure water temperature. Weather stations located above the cave and from a local climate station documented surface air temperature. This seven-year study demonstrated that both resurgences, and in-cave sites proximal to surface recharge points displayed significant variation in water and air temperature hourly, daily and seasonally as well as during storm events. In-cave sites that were located farthest from surface recharge showed very little fluctuation in water and air temperature and corresponded to the mean annual temperature of the area. These results offer important implications in terms of the study of aquifer vulnerability to surface contaminants, cave ecosystems, speleothem development, and thermodynamic controls on subterranean karst processes.