Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept
Résumé
Past variations in the dynamics of the Australian
monsoon have been estimated from multi-proxy analysis of
a core retrieved in the Eastern Banda Sea. Records of coccolith
and pollen assemblages, spanning the last 150 000
years, allow reconstruction of past primary production in the
Banda Sea, summer moisture availability, and the length of
the dry season in northern Australia and southeastern Indonesia.
The amount of moisture available during the summer
monsoon follows typical glacial/interglacial dynamics with
a broad asymmetrical 100-kyr cycle. Primary production
and length of the dry season appear to be closely related,
given that they follow the precessional cycle with the same
phase. This indicates their independence from ice-volume
variations. The present inter-annual variability of both parameters
is related to El Ni˜no Southern Oscillation (ENSO),
which modulates the Australian Winter Monsoon (AWM).
The precessional pattern observed in the past dynamics of
the AWM is found in ENSO and monsoon records of other
regions. A marked shift in the monsoon intensity occurring
during the mid Holocene during a period of constant ice volume,
suggests that low latitude climatic variation precedes
increases in global ice volume. This precessional pattern suggests
that a common forcing mechanism underlies low latitude
climate dynamics, acting specifically and synchronously
on the different monsoon systems.
Origine : Publication financée par une institution
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