Caves provide early warning of unprecedented decrease in rainfall recharge of groundwater
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Date
2022-05-02
Journal Title
Journal ISSN
Volume Title
Publisher
Research Square
Abstract
Billions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. In this study, five caves record a consistent response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s, characterised by a pronounced increase or ’uptick’ in dripwater and speleothem oxygen isotopic composition (δ18O). It is demonstrated that the uptick is in response to the shallow karst aquifers becoming disconnected from recharge due to regional drying. Our findings imply that rainfall recharge to groundwater across this region is no longer reliably occurring. Examination of the longer speleothem record shows that this is unprecedented over at least the last 800 years. A global network of cave dripwater monitoring would serve as an early warning of reduced groundwater recharge elsewhere, while evidence for upticks in speleothem paleoclimate records would provide a longer-term context to evaluate if current groundwater recharge changes are outside the range of natural variability. This study also validates speleothems as recorders of past hydroclimate via amplification of the δ18O signal by karst hydrology highlighting that speleothem δ18O are records of recharge, rather than a direct proxy for rainfall. © 2022 The Authors
Description
This preprint is a preliminary version of a manuscript that has not completed peer review at a journal. This work is licensed under a CC BY 4.0 License.
Keywords
Caves, Rain, Groundwater recharge, Climatic change, Oxygen isotopes, Paleoclimatology, Australia
Citation
Priestley, S., Treble, P., Griffiths, A., Baker, A., Abram, N., & Meredith, K. (2022). Caves provide early warning of unprecedented decrease in rainfall recharge of groundwater. (Preprint), Research Square. doi:10.21203/rs.3.rs-1556439/v1