Variability in the southern margin of the Indo-Australian Summer Monsoon since 46 ka

The past ∼ 50,000 years encompass a series of major climatic transitions, including Marine Isotope Stage 2, the Marine Isotope Stage 2/1 transition, and the onset of the Holocene, when the Earth underwent large shifts in temperature, ice volumes, sea levels and atmospheric circulation patterns. There is a growing body of research focused on the behaviour of the Indo-Australian Summer Monsoon (IASM) during these periods from sites close to Australia’s northern coastlines and currently within the zone of direct monsoon precipitation. However, the relative contributions of latitudinal shifts and/or moisture carrying capacity of the monsoon system on changes in hydroclimate remain uncertain. Here, we present the results from a 46,000-year sediment record obtained at the modern southern extent of rainfall penetration into north-west Australia associated with the IASM. Our results show that the region experienced reduced precipitation until the end of the glacial. During the MIS 2/1 transition and the early Holocene, there is evidence of an increase in wet-season precipitation, likely limited to extreme events occasionally reaching the site. More pronounced and sustained shifts in precipitation were limited to the late Holocene, during which the variability recorded at the site aligned with that interpreted from records further to the north in Australia. We interpret this as reflecting a time-transgressive southward shift in the southern limit of the monsoon system.