An isotopic calibration study of precipitation, cave dripwater, and climate in west‐central Florida

Abstract

Abstract:A calibration study of oxygen and hydrogen isotopic composition from precipitation and cave dripwater was conducted in westcentral Florida at Legend Cave during 2007. This study was performed to better understand how modern precipitation patterns can be discerned through examination of cave dripwater and speleothem calcite for paleoclimate reconstruction. The 'amount effect' was shown to be a dominant control on the oxygen isotopic composition of precipitation for the study area. A meteoric water line with a slope of 6Ð7 suggests evaporative effects occur either during precipitation or subsequent hydrological processes. However, υ18 O values of cave dripwater averaged near the mean annual amount-weighted average of precipitation, suggesting that the isotopic composition of dripwater tracks the long-term average of rainfall. An observed weak seasonal influence occurred in the d-excess values, with summer precipitation being more enriched due to increased evaporative effects. Comparison of precipitation υ18 O values to synoptic weather data shows the dominant amount effect influence occurs due to strong convective storms producing highly 18 O-depleted rainfall at greater amounts during the year. Constant υ 18 O values of the dripwater indicate that paleoclimate reconstructions using speleothems from this area would record changes in annual to interannual shifts in precipitation amount above the cave.

Drivers of precipitation stable oxygen isotope variability in an alpine setting, Snowy Mountains, Australia

“…Amour et al, 2010;Polk et al, 2012]. Suitable archives which preserve both hydrogen ( O) stable isotope data include polar ice sheets, midlatitude and low-latitude glaciers, and groundwater [Rozanski et al, 1997].…”

“…Stable isotopic signatures preserved in natural archives are routinely used to reconstruct palaeoenvironmental conditions [Rozanski et al, 1997;McDermott, 2004;St. Amour et al, 2010;Polk et al, 2012]. Suitable archives which preserve both hydrogen ( 2 H/ 1 H) and oxygen ( 18 O/ 16 O) stable isotope data include polar ice sheets, midlatitude and low-latitude glaciers, and groundwater [Rozanski et al, 1997].…”

Use of Molecular Markers to Compare Escherichia coli Transport with Traditional Groundwater Tracers in Epikarst

“…Water and contaminants can be stored in epikarst for considerable periods of time (White, 1988; Aley, 1997; Polk et al, 2012), as seen in studies where dyes and other solute tracers were flushed by storm discharge as long as 1 yr after tracer application (Ravbar et al, 2012; Kogovsek and Petric, 2014; Lauber and Goldscheider, 2014). The storage capacity of epikarst depends on its maturity (Klimchouk, 2000) and is controlled by its thickness, porosity, and the relative rates of inflow and outflow (Ford and Williams, 2007).…”

A multimethod approach to inform epikarst drip discharge modelling: Implications for palaeo‐climate reconstruction

“…A recent study from Harrie Wood Cave at the Yarrangobilly Caves found only a weak link between depth (−18 to −32 m) and mean ( r 2 = .3), and maximum discharge ( r 2 = .31), and the link between depth and discharge lag time was only marginally stronger ( r 2 = .52; Markowska et al, ). Markowska et al () did not consider isotopic variability of drip waters; however, other work from around the world has shown that drip‐water geochemical and isotopic values can vary over a range of temporal and spatial scales, and that these values can be impacted by subsurface processes (e.g., mixing and evaporation; Baldini, Mcdermott, & Fairchild, ; Cobb et al, ; Fairchild et al, ; Polk, van Beynen, & Wynn, ; Riechelmann et al, ). Clearly, the heterogeneity of the medium does not allow for generalised assumptions between depth, hydrological pathways, and associated palaeo‐climate proxy records.…”