Extensive Intrusion of Antarctic Intermediate Water into the Arabian Sea during Younger Dryas

Antarctic Intermediate Water (AAIW) plays a crucial role in the global thermohaline circulation and is a vital component of the Atlantic Meridional Overturning Circulation (AMOC). It significantly contributes to the redistribution of heat, oxygen, and nutrients across the global ocean. Understanding the dynamics of intermediate water circulation over millennial timescales is essential for evaluating how changes in the AMOC affect ocean heat transport during abrupt climatic events. Despite its importance, the relationship between global intermediate water circulation and abrupt high-latitude climatic events such as the Younger Dryas (YD) and Heinrich Stadials (HS) remains partly understood, particularly in the Indian Ocean. To address this gap, we present a high-resolution ~29 kyr record of Neodymium isotopes (Ɛ_Nd) from the authigenic phases of a sediment core (SK-17) collected at 840 m depth in the eastern Arabian Sea, off Goa. Our Ɛ_Nd data shows significant temporal variations from -9.5 to -6.1 throughout the core. Climatic periods (such as YD and HS) with enhanced radiogenic Nd signatures indicate increased northward penetration of AAIW into the northern Indian Ocean during these intervals. These episodes correspond to colder periods in the Northern Hemisphere, suggesting a direct linkage between Northern Hemisphere climate dynamics and the formation of AAIW in the Southern Ocean. Specifically, the enhanced formation of AAIW during these times may have been driven by warming-induced deceleration of the AMOC, which likely triggered increased AAIW production in the Southern Ocean. This connection highlights the interplay between the North Atlantic Deep-Water formation and Southern Ocean climate processes governed by the "bipolar seesaw" mechanism. By linking AAIW variability in the Arabian Sea to global climatic events, our study underscores the importance of intermediate water masses in understanding the mechanisms driving past and potential future changes in the AMOC.