Post-glacial coupling of the Australasian monsoon and teleconnections to the North Atlantic: new insights from Indonesian speleothems
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Date
2009-05-15
Journal Title
Journal ISSN
Volume Title
Publisher
GNS Science
Abstract
The Australasian monsoon system orchestrates rainfall variability and terrestrial
productivity in the densely populated region of the tropical Indo-Pacific. A clear
understanding of the dominant mechanisms governing its variability has been difficult
to resolve, partly because we currently lack high-resolution proxy records of past
monsoon behaviour, particularly for the southern tropics. Here we provide a
radiometrically dated reconstruction of Australian-Indonesian summer monsoon
(AISM) rainfall based on oxygen isotopes and trace element data in stalagmites from
southern Indonesia. The multi-proxy records are tied to age-depth models constructed
from 62 TIMS and MC-ICP-MS U-series ages, covering the period 0 to 12.6 ka B.P.
The record shows that the AISM was anti-phased with the East Asian summer
monsoon (EASM) on orbital to millennial-centennial timescales over the past 12.6 ka.
At the orbital-scale, local summer insolation was an important driver of opposing
changes in AISM and EASM rainfall. However, a slight mismatch between the AISM
and insolation from 9 to 11 ka B.P. is concurrent with the sharp rise in eustatic sealevel,
which apparently increased the supply of northwesterly summer monsoon
moisture to the Indonesian maritime continents.
At millennial-centennial timescales, the oxygen isotope and trace element records
show that periods of weakened North Atlantic meridional overturning circulation and
cooling, including the Younger Dryas cold stage, are in phase with sharp increases in
AISM rainfall. The connection between the AISM and a cooler North Atlantic is
probably due to enhanced outflow from the Asian winter monsoon and associated
southward migration of the intertropical convergence zone. These interhemispheric
connections were dominant until ~6.5 ka, when the El NiƱo-Southern Oscillation
became the governing influence on AISM variability.
Description
Keywords
Australia, Monsoons, Rain, Tropical regions, Elements, Trace amounts, Indonesia, Asia, Southern Oscillation
Citation
Griffiths, M., Drysdale, R., Gagan, M., Zhao, J.-x., Ayliffe, L., Hellstrom, J., Hantoro, W., Frisia, S., Feng, Y-x., Cartwright, I., St Pierre, E., Fischer, M., & Suwargadi, B. (2009). Post-glacial coupling of the Australasian monsoon and teleconnections to the North Atlantic: new insights from Indonesian speleothems. Paper presented at the Past Climates meeting, Wellington New Zealand, May 15-17, 2009.