Publikationsdatum:
2016-07-06
Beschreibung:
Orbital to millennial scale variations in Asian monsoon speleothem δ 18 O have been widely interpreted as records of monsoon intensity and/or rainfall amount. To assess the influence of these and other mechanisms on higher-frequency δ 18 O variability, we utilize simulations from a spectrally nudged isotope-enabled general circulation model coupled with instrumental climate data to investigate the climatic controls on interannual precipitation δ 18 O (δ 18 O p ) variability at four key cave locations affected by the Asian monsoon: Qunf Cave, Oman; Mawmluh Cave, India; Tham Mai Cave, Laos; and Dongge Cave, China. Comparison with instrumental climate data show that interannual δ 18 O p variations are only weakly related to local precipitation amount at the four sites, and are instead controlled primarily by large-scale monsoon intensity and upstream precipitation over the tropical Indo-Pacific region, which influence the δ 18 O of incoming moisture. Spatial correlations with sea surface temperature and precipitation, composite analyses, and time series analyses show that the El Niño Southern Oscillation (ENSO) also plays a key role in modulating interannual precipitation δ 18 O p variability in the region, especially in northern India and Southeast Asia, with positive δ 18 O p anomalies during El Niño years reflecting increased contribution of high δ 18 O moisture from the nearby Bay of Bengal. Coherent interannual to decadal δ 18 O variations seen in high-resolution proxy records from across the Asian Monsoon region, likely record monsoon intensity and upstream rainout, whereas ENSO related variability is likely to be strongest in records from northern India and Southeast Asia, with the largest anomalies expected when weak monsoons and El Niño occur together.
Print ISSN:
0148-0227
Thema:
Geologie und Paläontologie
,
Physik
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