Glacial Indonesian Throughflow weakening across the Mid-Pleistocene Climatic Transition

The Indonesian Throughflow (ITF) is a gateway controlling the flow of heat and salt between the Pacific and Indian Oceans and is thought to play an important role in modulating the meridional overturning circulation. However, the behavior of the ITF across the Mid-Pleistocene Climatic Transition (MPT), is unknown. Here we report new sea surface temperature (SST) and aridity (Ti/Ca) records from the west coast of Australia (IODP Site U1460), spanning the past 2.5 Ma. Our records show a decrease in glacial temperatures around 1.5 Ma, and 0.6 Ma, suggesting a restriction of the ITF during these intervals. These SST drops coincide with changes in benthic d¹³C gradients across the Atlantic and Pacific basins, suggesting that the restriction of the ITF could have influenced the evolution of global ocean circulation. This is the first evidence of possible influence of the ITF on the thermohaline circulation over the MPT. In addition, our Ti/Ca record provides evidence of a long-term increase in glacial aridity and an intensification of G/IG oscillations that mirrors the evolution of the SST changes, suggesting that the dynamics of the ITF could have impacted the development of the hydrological cycle in Western Australia.