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Transformation of ENSO‐related rainwater to dripwater δ 18 O variability by vadose water mixing
Author(s) -
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.
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl061696
Subject(s) - stalagmite , speleothem , vadose zone , rainwater harvesting , el niño southern oscillation , climatology , karst , geology , series (stratigraphy) , hydrology (agriculture) , residence time (fluid dynamics) , environmental science , atmospheric sciences , cave , soil water , soil science , holocene , geography , oceanography , ecology , paleontology , geotechnical engineering , archaeology , biology
Speleothem oxygen isotopes ( δ 18 O) are often used to reconstruct past rainfall δ 18 O 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 δ 18 O time series from northern Borneo and compare them to local rainfall δ 18 O variability. We demonstrate that vadose water mixing is the primary rainfall‐to‐dripwater transformation process at our site, where dripwater δ 18 O reflects amount‐weighted rainfall δ 18 O integrated over the previous 3–10 months. We document large interannual dripwater δ 18 O 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 δ 18 O time series given different dripwater residence times. Our study highlights the utility of generating multiyear, paired time series of rainfall and dripwater δ 18 O to aid interpretations of stalagmite δ 18 O reconstructions.