Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

International audiencePast variations in the dynamics of the Australianmonsoon have been estimated from multi-proxy analysis ofa core retrieved in the Eastern Banda Sea. Records of coccolithand pollen assemblages, spanning the last 150 000years, allow reconstruction of past primary production in theBanda Sea, summer moisture availability, and the length ofthe dry season in northern Australia and southeastern Indonesia.The amount of moisture available during the summermonsoon follows typical glacial/interglacial dynamics witha broad asymmetrical 100-kyr cycle. Primary productionand length of the dry season appear to be closely related,given that they follow the precessional cycle with the samephase. This indicates their independence from ice-volumevariations. The present inter-annual variability of both parametersis related to El Ni˜no Southern Oscillation (ENSO),which modulates the Australian Winter Monsoon (AWM).The precessional pattern observed in the past dynamics ofthe AWM is found in ENSO and monsoon records of otherregions. A marked shift in the monsoon intensity occurringduring the mid Holocene during a period of constant ice volume,suggests that low latitude climatic variation precedesincreases in global ice volume. This precessional pattern suggeststhat a common forcing mechanism underlies low latitudeclimate dynamics, acting specifically and synchronouslyon the different monsoon systems