Proxy records of the Indonesian Low and the El Nino-Southern Oscillation (ENSO) from stable isotope ...

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منو

" Proxy records of the Indonesian Low and the El Nino-Southern Oscillation (ENSO) from stable isotope measurements of Indonesian reef corals "
M. D. Moore J. H. Lipps

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113283
Doc. No	:	TLpq304185470
Main Entry	:	J. H. Lipps
	:	M. D. Moore
Title & Author	:	Proxy records of the Indonesian Low and the El Nino-Southern Oscillation (ENSO) from stable isotope measurements of Indonesian reef corals\ M. D. MooreJ. H. Lipps
College	:	University of California, Berkeley
Date	:	1995
student score	:	1995
Degree	:	Ph.D.
Page No	:	357
Abstract	:	The Earth's largest atmospheric convective center is the Indonesian Low. It generates the Australasian monsoon, drives the zonal tropospheric Walker Circulation, and is implicated in the genesis of the El Nino-Southern Oscillation (ENSO). The long-term variability of the Indonesian Low is poorly characterized, yet such information is crucial for evaluating whether changes in the strength and frequency of ENSO events are a possible manifestation of global warming. Stable oxygen isotope ratios (usd\delta\spusdO) in shallow-water reef coral skeletons track tropical convective activity over hundreds of years because the input of isotopically-depleted rainwater dilutes seawater usd\delta\spusdO. Corals also impose a temperature-dependent fractionation on usd\delta\spusdO, but where annual rainfall is high and sea surface temperature (SST) variability is low the freshwater flux effect dominates. The Indonesian Seaway has high annual precipitation, large precipitation seasonality, minor SST variability and short surface water residence times. These factors maximize the sensitivity of seawater water usd\delta\spusdO to freshwater flux and thus provide an opportunity to use coral usd\delta\spusdO to study the past variability of the Indonesian LOW. Monthly-resolution stable isotope records were developed from Porites cores from key sites by automated gas-source mass spectrometry. The usd\delta\spusdO records were examined for their reproducibility, noise levels, periodicities, secular trends, and fidelity to the Australasian instrument record. The usd\delta\spusdO records are most reproducible and reliable on interannual timescales. Cross-spectral analysis reveals significant coherency to the Darwin SLP pressure record at ENSO periodicities. Singular-spectrum analysis reveals that the time-evolution of ENSO-bandwidth modes in the coral usd\delta\spusdO records are nearly identical to those in the Darwin SLP record. The most accurate coral usd\delta\spusdO records are from sites on the Pacific-Indian Ocean throughflow route with either large seasonal salinity variability or strong air-sea interactions. Secular trends in the usd\delta\spusdO records are inconsistent and are considered artifacts of coral growth dynamics. These results provide a foundation for extending the Indonesian coral usd\delta\spusdO records into the pre-historical period, and suggest that hindcasting of the ENSO-related variability of the Indonesian Low can be achieved with acceptable levels of confidence.
Subject	:	Earth sciences
	:	Geochemistry
	:	Oceanography
	:	Paleontology
	:	Paleontology