Transformation of ENSO-related rainwater to dripwater [delta]18O variability by vadose water mixing

Speleothem oxygen isotopes ([delta]18O) are often used to reconstruct past rainfall [delta]18O variability, and thereby hydroclimate changes, in many regions of the world. However, poor constraints on the karst hydrological processes that transform rainfall signals into cave dripwater add significan...

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Bibliographic Details
Published inGeophysical research letters Vol. 41; no. 22; p. 7907
Main Authors Moerman, Jessica W, Cobb, Kim M, Partin, Judson W, Meckler, A Nele, Carolin, Stacy A, Adkins, Jess F, Lejau, Syria, Malang, Jenny, Clark, Brian, Tuen, Andrew A
Format Journal Article
LanguageEnglish
Published Washington John Wiley & Sons, Inc 28.11.2014
Subjects
Amplitudes
Asymmetry
Correlation
El Nino
El Nino phenomena
El Nino-Southern Oscillation event-rainfall relationships
Genetic transformation
Hydroclimate
Hydrology
Isotopes
Karst
Meteorology
Offsets
Oxygen
Oxygen isotopes
Rain
Rain water
Rainfall
Southern Oscillation
Time series
Uncertainty
Vadose water
Variability
Water mixing
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Summary:Speleothem oxygen isotopes ([delta]18O) are often used to reconstruct past rainfall [delta]18O variability, and thereby hydroclimate changes, in many regions of the world. However, poor constraints on the karst hydrological processes that transform rainfall signals into cave dripwater add significant uncertainty to interpretations of speleothem-based reconstructions. Here we present several 6.5 year, biweekly dripwater [delta]18O time series from northern Borneo and compare them to local rainfall [delta]18O variability. We demonstrate that vadose water mixing is the primary rainfall-to-dripwater transformation process at our site, where dripwater [delta]18O reflects amount-weighted rainfall [delta]18O integrated over the previous 3-10 months. We document large interannual dripwater [delta]18O variability related to the El Niño-Southern Oscillation (ENSO), with amplitudes inversely correlated to dripwater residence times. According to a simple stalagmite forward model, asymmetrical ENSO extremes produce significant offsets in stalagmite [delta]18O time series given different dripwater residence times. Our study highlights the utility of generating multiyear, paired time series of rainfall and dripwater [delta]18O to aid interpretations of stalagmite [delta]18O reconstructions.
ISSN:0094-8276
1944-8007
DOI:10.1002/2014GL061696