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Diurnal to interannual rainfall δ^(18)O variations in northern Borneo driven by regional hydrology

Moerman, Jessica W. and Cobb, Kim M. and Adkins, Jess F. and Sodermann, Harald and Clark, Brian and Tuen, Andrew A. (2013) Diurnal to interannual rainfall δ^(18)O variations in northern Borneo driven by regional hydrology. Earth and Planetary Science Letters, 369 . pp. 108-119. ISSN 0012-821X. doi:10.1016/j.epsl.2013.03.014.

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The relationship between climate variability and rainfall oxygen isotopic (δ^(18)O) variability is poorly constrained, especially in the tropics, where many key paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate. Here we present a daily-resolved, 5-yr-long timeseries of rainfall δ^(18)O from Gunung Mulu National Park, located in northern Borneo (4°N, 114°E) in the heart of the West Pacific Warm Pool, and compare it to local and regional climatic variables. Daily rainfall δ^(18)O values range from +0.7‰ to −18.5‰ and exhibit a weak but significant inverse relationship with daily local precipitation amount (R=−0.19, p<0.05), consistent with the tropical amount effect. Day-to-day δ^(18)O variability at Mulu is best correlated to regional precipitation amount averaged over the preceding week (R=−0.64, p<0.01). The inverse relationship between Mulu rainfall δ^(18)O and local (regional) precipitation amount increases with increased temporal averaging, reaching R=−0.56 (R=−0.72) on monthly timescales. Large, negative, multi-day rainfall δ^(18)O anomalies of up to 16‰ occur every 30–90 days and are closely associated with wet phases of the intraseasonal Madden–Julian Oscillation. A weak, semi-annual seasonal cycle in rainfall δ^(18)O of 2–3‰ bears little resemblance to seasonal precipitation variability, pointing to a complex sequence of moisture sources and/or trajectories over the course of the year. Interannual rainfall δ^(18)O variations of 6–8‰ are significantly correlated with indices of the El Niño Southern Oscillation, with increased rainfall δ^(18)O during relatively dry El Niño conditions, and vice versa during La Nina events. We find that Mulu rainfall δ^(18)O outperforms Mulu precipitation amount as a tracer of basin-scale climate variability, highlighting the time- and space-integrative nature of rainfall δ^(18)O. Taken together, our results suggest that rainfall δ^(18)O variability at Mulu is significantly influenced by the strength of regional convective activity. As such, our study provides further empirical support for the interpretation of δ^(18)O-based paleo-reconstructions from northern Borneo stalagmites as robust indicators of regional-scale hydroclimate variability, where higher δ^(18)O reflects regional drying.

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Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2013 Elsevier B. V. Received 4 October 2012; Received in revised form 11 March 2013; Accepted 13 March 2013; Editor: G. Henderson. Available online 25 April 2013. The authors gratefully acknowledge the Mulu Meteorological Station staff for overseeing the collection of the daily rainfall samples, as well as Jenny Malang, Syria Lejau, and the staff at Gunung Mulu National Park for their dedicated assistance during fieldtrips. Permits for this work were granted by the Malaysian Economic Planning Unit, the Sarawak State Planning Unit, and the Sarawak Forestry Department. We also thank Aaron van Pelt of Picarro, Inc., Bruce Vaughn of INSTARR at UC Boulder, and Krystle Stewart for their invaluable assistance during sample analysis and Dr. Emanuele Di Lorenzo for his assistance with the TRMM dataset. This research was supported by NSF Grant 0645291 to KMC, and JWM was funded by a NSF Graduate Research Fellowship.
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NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:rainfall oxygen isotopes; Madden–Julian oscillation; amount effect; stalagmite; paleoclimate; El Niño southern oscillation
Record Number:CaltechAUTHORS:20130820-091932864
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Official Citation:Jessica W. Moerman, Kim M. Cobb, Jess F. Adkins, Harald Sodemann, Brian Clark, Andrew A. Tuen, Diurnal to interannual rainfall δ18O variations in northern Borneo driven by regional hydrology, Earth and Planetary Science Letters, Volumes 369–370, May 2013, Pages 108-119, ISSN 0012-821X,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40729
Deposited On:20 Aug 2013 21:35
Last Modified:10 Nov 2021 00:07

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