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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 11
Hydrol. Earth Syst. Sci., 20, 4625–4640, 2016
https://doi.org/10.5194/hess-20-4625-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 20, 4625–4640, 2016
https://doi.org/10.5194/hess-20-4625-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Nov 2016

Research article | 17 Nov 2016

ENSO–cave drip water hydrochemical relationship: a 7-year dataset from south-eastern Australia

Carol V. Tadros1,2, Pauline C. Treble1,2, Andy Baker2, Ian Fairchild3,4, Stuart Hankin1, Regina Roach5, Monika Markowska1,2, and Janece McDonald6 Carol V. Tadros et al.
  • 1Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
  • 2Connected Waters Initiative Research Centre, UNSW Australia, Kensington NSW 2052, Australia
  • 3School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
  • 4Birmingham Institute for Forest Research, University of Birmingham, Edgbaston, Birmingham, UK
  • 5NSW National Parks and Wildlife Service, Sydney, NSW, Australia
  • 6Environmental and Climate Change Research Group, School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia

Abstract. Speleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. This paper presents the first extensive hydrochemical and δ18O dataset from Harrie Wood Cave, in the Snowy Mountains, south-eastern (SE) Australia. Using a 7-year long rainfall δ18O and drip-water Ca, Cl, Mg / Ca, Sr / Ca and δ18O datasets from three drip sites, we determined that the processes of mixing, dilution, flow path change, carbonate mineral dissolution and prior calcite precipitation (PCP) accounted for the observed variations in the drip-water geochemical composition. We identify that the three monitored drip sites are fed by fracture flow from a well-mixed epikarst storage reservoir, supplied by variable concentrations of dissolved ions from soil and bedrock dissolution. We constrained the influence of multiple processes and controls on drip-water composition in a region dominated by El Niño–Southern Oscillation (ENSO). During the El Niño and dry periods, enhanced PCP, a flow path change and dissolution due to increased soil CO2 production occurred in response to warmer than average temperatures in contrast to the La Niña phase, where dilution dominated and reduced PCP were observed. We present a conceptual model, illustrating the key processes impacting the drip-water chemistry. We identified a robust relationship between ENSO and drip-water trace element concentrations and propose that variations in speleothem Mg / Ca and Sr / Ca ratios may be interpreted to reflect palaeorainfall conditions. These findings inform palaeorainfall reconstruction from speleothems regionally and provide a basis for palaeoclimate studies globally, in regions where there is intermittent recharge variability.

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We investigated the potential use of trace element and stable oxygen-isotope variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. Using 7 years of cave monitoring data, we constrained the hydrological processes impacting the drip-water composition and identified a robust ENSO–drip water hydrochemical relationship. These findings are fundamental for reconstructing past ENSO variability from speleothems (cave deposits) regionally and globally.
We investigated the potential use of trace element and stable oxygen-isotope variations in cave...
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