Abstract

Understanding changes in ocean circulation during the last deglaciation is crucial to unravelling the dynamics of glacial-interglacial and millennial climate shifts. Neodymium (Nd) isotope records measured on Fe-Mn oxide leaches from marine sediment cores have been used to reconstruct changes in Atlantic deep water mixing and structure. We present new tests of marine Nd extraction, and new widely distributed records. Taken as a whole, these records provide a coherent reconstruction of glacial Atlantic deep circulation, which is consistent with benthic d13C reconstructions, and suggests major changes in water mass strength and structure during the last deglaciation. Neodymium isotope measurements from deep western North Atlantic at the Bermuda Rise allow comparison of our deep water source record with overturning strength proxies. This comparison shows that both deep water mass source and overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast any freshwater perturbation caused by Heinrich event 1, could have only affected shallow overturning illustrating the difference between changes in upper-ocean overturning associated with millennial-scale events, and whole ocean deglacial climate events.