The Australian-Indonesian monsoon is an important component of the climate system in
the tropical Indo-Pacific region. However, its past variability, relation with northern
and southern high latitude climate and connection to the other Asian monsoon systems
are poorly understood. Here we present high-resolution records of monsoon-controlled
austral winter upwelling during the past 22,000 years, based on planktic foraminiferal
oxygen isotope and faunal composition in a sedimentary archive collected offshore
southern Java. We show that glacial-interglacial variations in the Australian-Indonesian
winter monsoon were in phase with the Indian summer monsoon system, consistent with
their modern linkage through cross-equatorial surface winds. Likewise, millennial-scale
variability of upwelling shares similar sign and timing with upwelling variability in the
Arabian Sea. On the basis of element composition and grain-size distribution as
precipitation-sensitive proxies in the same archive, we infer that (austral) summer
monsoon rainfall was highest during the Bølling-Allerød period and the past 2,500 years.
Our results indicate drier conditions during Heinrich Stadial 1 due to a southward shift
of summer rainfall and a relatively weak Hadley Cell south of the Equator. We suggest
that the Australian-Indonesian summer and winter monsoon variability were closely
linked to summer insolation and abrupt climate changes in the northern hemisphere.
