Global distribution and controls on cave drip water oxygen isotope composition
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Date
2018-12-10
Journal Title
Journal ISSN
Volume Title
Publisher
Australasian Quaternary Association Inc
Abstract
The oxygen isotope composition of speleothems is a widely utilised paleoclimate proxy that is
responsible for the current state-of-knowledge of past Asian monsoon dynamics, the timing of
glacial-interglacial cycles, and the insolation control on inter-tropical convergence zone position,
among other climate processes. Because speleothems are deposited by cave drip water, and this is
derived from meteoric precipitation, it is critical to understand the empirical relationship between
precipitation and cave drip water d18O. Here, we present the first global analysis, based on data
from 148 drip sites, 38 caves, and five continents. Globally, drip water d18O is most similar to the
amount-weighted precipitation d18O where mean annual temperature (MAT) is < 10 °C. For
seasonal climates with MAT > 10 °C and < 16 °C, we demonstrate that drip water d18O records
the recharge-weighted d18O. Our analysis implies that speleothems (formed in near isotopic
equilibrium) are most likely to have d18O that directly reflect meteoric precipitation only in cool
climates. In warmer and drier environments, speleothems will have a seasonal bias toward the
precipitation d18O of recharge periods and, in some cases, the extent of evaporative fractionation of
stored karst water. We highlight the implications of our analysis for the interpretation of oxygen
isotope records in Australasian speleothems. © The Authors
Description
Keywords
Caves, Australia, Water, Oxygen, Isotopes, Climates, Monsoons, Asia, Glaciers, Thermodynamic cycles, Precipitation
Citation
Baker, A., Hartmann, A., Duan, W., Hankin, S., Comas-Bru, L., Cuthbert, M. O., Treble, P. C., Banner, J., Genty, D., Baldini, L., Bartolomé, M., Moreno, A., & Pérez-Mejías, C. (2018). Global distribution and controls on cave drip water oxygen isotope composition. Paper presented at the AQUA Biennial Conference, Canberra, 10-14th December 2018. (pp. 21). https://aqua.org.au/wp-content/uploads/2019/10/AQUA-2018-Program.pdf