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Modern speleothem oxygen isotope hydroclimate records in water-limited SE Australia

Markowska, Monika, Cuthbert, Mark O., Baker, Andy, Treble, Pauline C., Andersen, Martin S., Adler, Lewis, Griffiths, Alan and Frisia, Silvia 2020. Modern speleothem oxygen isotope hydroclimate records in water-limited SE Australia. Geochimica et Cosmochimica Acta 270 , pp. 431-448. 10.1016/j.gca.2019.12.007

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Dryland regions are generally projected to become drier under future climate change scenarios. Understanding the long-term natural variability of dryland regions via paleo-reconstructions is therefore highly desirable. The δ18O of two coeval modern speleothems from Cathedral Cave, Wellington, in semi-arid SE Australia are compared to the instrumental record to assess its efficacy as a proxy of past hydrological variability. Stalagmite δ18O was modulated by the frequency of recharge events and epikarst evaporation of storage water. Prolonged intervals between recharge events, such as droughts, resulted in higher stalagmite δ18O. Conversely, periods with more frequent recharge events and a positive water balance, resulted in lower δ18O. Disequilibrium cave processes are likely to be enhanced during dry conditions, although it is argued that these will modulate δ18Ospel in the same direction as epikarst evaporation, effectively amplifying the response of δ18Ospel. Extreme events, such as floods and droughts, were also captured in the stalagmite records, although potentially with a lag of several years. We verify that modern speleothems from semi-arid regions can be used to reconstruct hydroclimate due to variations in δ18Ospel modulated by karst processes. Such records are archives of past changes in recharge rather than precipitation amount or surface temperature, as is commonly applied to speleothem records from non-water-limited regions.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Environmental Sciences
Publisher: Elsevier
ISSN: 0016-7037
Date of First Compliant Deposit: 13 December 2019
Date of Acceptance: 7 December 2019
Last Modified: 13 Dec 2020 03:05

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