Deep-water coral records of glacial and recent ocean-atmosphere dynamics from the Perth Canyon in the southeast Indian Ocean

Abstract

We present radiocarbon and neodymium isotope records from accurately dated (U-series) live and fossil (<2 ka, 17.5 to 29.6 ka BP) deep-water corals, collected between 675 and 1788 m from the Perth Canyon, offshore southwest Australia. These records provide the first insights into recent and last glacial intermediate-deep water circulation and ventilation histories from the poorly represented southeast Indian Ocean. Ocean ventilation fluctuated significantly during the last glacial period, being highly ventilated during early Marine Isotope Stage 2 and the early deglaciation, yet less ventilated and more stratified during the Last Glacial Maximum. Furthermore, the Perth Canyon corals recorded a major and rapid (∼300 years) perturbation at 25 ka, indicating that mid-depth waters were exposed to poorly ventilated, unradiogenic Nd deeper waters. We link this to similar, age equivalent changes at geographically disparate sites from the southeast Atlantic to the Southern Ocean south of Tasmania, together with fluctuations in Antarctic sea-ice, oceanic fronts, and Atlantic Meridional Overturning Circulation (AMOC). This widespread Southern Ocean event indicates a transient breach in upper and lower ocean cell boundaries of the MOC, providing further evidence for the non-steady state, zonal dynamics of the glacial Southern Ocean.