The modern assessment of climate, calcite growth, and the geochemistry of cave drip waters as a precursor to paleoclimate study
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The overall goal of this study is to determine the resolution and type of proxy that any one drip site can provide for the determination of past climate. The study examines surface conditions (effective rainfall, temperature, PDSI), cave characteristics (cave geometry, cave air CO2, location), drip site characteristics (drip rate, drip rate response to rainfall), and drip water characteristics (pH, trace element ratios, alkalinity, temperature). The study encompasses two distinctly different caves, Inner Space Cavern (Chapter 2) and Westcave (Chapter 3). A goal of Chapter 2 is to identify drip sites where there is an intra-annual climate signal, which can assist with high resolution paleo-drought reconstructions when extended to speleothem studies. To be considered an intra-annual climate sensitive drip site, a site should display statistically significant correlations between (1) effective rainfall and drip rate; (2) effective rainfall and Mg/Ca; (3) drip rate and Mg/Ca; (4) Palmer Drought Severity Index (PDSI) and drip rate; and (5) PDSI and Mg/Ca. These relationships can be explained by the extent to which water flux in the karst overburden influences flow path characteristics, water residence time, and water-rock interactions. The data in Chapter 3 will indicate that (1) variations in trace element/Ca values in cave drip waters are temperature dependent and vary on a seasonal time scale, (2) the standardization of trace element/Ca values allows for between drip site comparisons, (3) the standardization of trace element/Ca values can add statistical power to statistical analyses by increasing the sample size, (4) calcite growth rates follow a seasonal pattern based on variations in surface temperature, (5) a regional drought indicator provides correlation with trace element/Ca values at some drip sites and this relationship is most likely dependent upon temperature.