Indonesian Throughflow variability during the last 140 ka: the Timor Sea outflow

Abstract

Abstract The transfer of surface and intermediate water from the Pacific to Indian Ocean through the Indonesian passages (Indonesian Throughflow: ITF) strongly influences the heat and freshwater budgets of tropical water masses, in turn affecting global climate. Here, we use combined δ 18 O and Mg/Ca analyses of surface and thermocline planktonic foraminifers to estimate variations in sea surface temperature, salinity and mixed layer thickness over the last 140 ka. Comparison of water mass properties reveals a steeper thermocline temperature gradient in the Timor Strait than in the eastern Indian Ocean during glacials, implying a decrease in ITF cool thermocline outflow. A major freshening and cooling of thermocline waters occurred at c . 9.5 ka, when sea level rose above a critical threshold, allowing establishment of a shallow marine connection from the South China Sea to the Java Sea. Comparison of benthic δ 13 C profiles ( c . 1800 to 3000 m water depth) suggests vigorous mixing of Indian Ocean and ITF outflow intermediate waters during interglacials. In contrast, deep and intermediate water masses became more stratified during glacials. Lower δ 13 C values at c . 3000 m water depth reflect a decrease in deepwater ventilation, probably related to slowdown of the global thermohaline circulation during glacials.