Semi-arid zone caves: evaporation and hydrological controls on δ18O drip water composition and implications for speleothem paleoclimate reconstructions

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dc.contributor.authorMarkowska, Men_AU
dc.contributor.authorBaker, AAen_AU
dc.contributor.authorAndersen, MSen_AU
dc.contributor.authorJex, CNen_AU
dc.contributor.authorCuthbert, MOen_AU
dc.contributor.authorRau, GCen_AU
dc.contributor.authorGraham, PWen_AU
dc.contributor.authorRutlidge, Hen_AU
dc.contributor.authorMariethoz, Gen_AU
dc.contributor.authorMarjo, CEen_AU
dc.contributor.authorTreble, PCen_AU
dc.contributor.authorEdwards, Nen_AU
dc.date.accessioned2016-05-19T02:02:09Zen_AU
dc.date.available2016-05-19T02:02:09Zen_AU
dc.date.issued2016-01-01en_AU
dc.date.statistics2016-05-19en_AU
dc.description.abstractOxygen isotope ratios in speleothems may be affected by external processes that are independent of climate, such as karst hydrology and kinetic fractionation. Consequently, there has been a shift towards characterising and understanding these processes through cave monitoring studies, particularly focussing on temperate zones where precipitation exceeds evapotranspiration. Here, we investigate oxygen isotope systematics at Wellington Caves in semi-arid, SE Australia, where evapotranspiration exceeds precipitation. We use a novel D2O isotopic tracer in a series of artificial irrigations, supplemented by pre-irrigation data comprised four years of drip monitoring and three years of stable isotope analysis of both drip waters and rainfall. This study reveals that: (1) evaporative processes in the unsaturated zone dominate the isotopic composition of drip waters; (2) significant soil zone ‘wetting up’ is required to overcome soil moisture deficits in order to achieve infiltration, which is highly dependent on antecedent hydro-climatic conditions; (3) lateral flow, preferential flow and sorption in the soil zone are important in redistributing subsurface zone water; (4) isotopic breakthrough curves suggest clear evidence of piston-flow at some drip sites where an older front of water discharged prior to artificial irrigation water; and (5) water residence times in a shallow vadose zone (<2 m) are highly variable and can exceed six months. Oxygen isotope speleothem records from semi-arid regions are therefore more likely to contain archives of alternating paleo-aridity and paleo-recharge, rather than paleo-rainfall e.g. the amount effect or mean annual. Speleothem-forming drip waters will be dominated by evaporative enrichment, up to ∼3‰ in the context of this study, relative to precipitation-weighted mean annual rainfall. The oxygen isotope variability of such coeval records may further be influenced by flow path and storage in the unsaturated zone that is not only drip specific but also influenced by internal cave climatic conditions, which may vary spatially in the cave.© 2015, Elsevier Ltd.en_AU
dc.identifier.citationMarkowska, M., Baker, A., Andersen, M. S., Jex, C. N., Cuthbert, M. O., Rau, G. C., Graham, P. W., Rutlidge, H., Mariethoz, G., Marjo, C. W., Treble, P. C, & Edwards, N. (2016). Semi-arid zone caves: evaporation and hydrological controls on δ18O drip water composition and implications for speleothem paleoclimate reconstructions. Quaternary Science Reviews, 131(Part B), 285-301. doi:10.1016/j.quascirev.2015.10.024en_AU
dc.identifier.govdoc6402en_AU
dc.identifier.issn0277-3791en_AU
dc.identifier.issuePart Ben_AU
dc.identifier.journaltitleQuaternary Science Reviewsen_AU
dc.identifier.pagination285-301en_AU
dc.identifier.urihttps://doi.org/10.1016/j.quascirev.2015.10.024en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/6821en_AU
dc.identifier.volume131en_AU
dc.language.isoenen_AU
dc.publisherElsevier B.V.en_AU
dc.subjectZonesen_AU
dc.subjectEvaporationen_AU
dc.subjectHydrologyen_AU
dc.subjectPaleoclimatologyen_AU
dc.subjectIsotopesen_AU
dc.subjectSoilsen_AU
dc.titleSemi-arid zone caves: evaporation and hydrological controls on δ18O drip water composition and implications for speleothem paleoclimate reconstructionsen_AU
dc.typeJournal Articleen_AU
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