Neodymium isotopic evidence for linked changes in Southeast Atlantic and Southwest Pacific circulation over the last 200 kyr

摘要: Knowledge of the geometry and strength deep overturning circulation is central to understanding past climate variability on glacial–interglacial (G–I) timescales. In this study, neodymium (Nd) isotopic ratios planktonic foraminifera are used reconstruct water mass source mixing history intermediate in Southeast (SE) Atlantic Southwest (SW) Pacific over 200 kyr from five sediment cores. Nd isotopes a depth transect cores SE displayed stronger geochemical gradient around 3.5 km at LGM, with higher eNd values ∼−6.0 below that boundary than those ∼−7.8 above. contrast, similar value (∼−9.5) observed both abyssal depths Holocene. The glacial upper ocean 1.8 units less radiogenic lower ocean, reflecting an increase amount North Component Water (NACW) Atlantic. A coherent isotope change was SW major excursion more during Marine Isotope Stage (MIS) 2, 4 6. This suggests flux NACW Southern Ocean reduced cold marine stages, possibly accompanied by changes geometry. constant 2 eNd-unit offset between persistent propagation last cycle. Moreover, larger vertical gradients waters indicate decreased proportion entrainment into oceans, consistent studies proposing meridional cells.