Large-scale Pacific-sourced intrusion into the glacial South Atlantic

Abstract

The deep Southern Ocean (SO) circulation plays a key role in the storage and release of CO2 in Earth’s climate system. Uptake and release of CO2 strongly depend on the redistribution of well and poorly ventilated water masses. Here, we present new neodymium isotope data (εNd) from three sediment cores from the Atlantic sector of the SO to assess the distribution of water masses during the past 150 ka. ODP 1094 (2807 m) reveals a tremendous Holocene εNd-variability (-0.25 to -6.07), which most likely reflects local influences. PS 1768-8 (3299 m) and ODP 1093 (3624 m), show far more unradiogenic interglacial εNd-signatures, which are similar to the present-day Antarctic Bottom Water (AABW) (εNd~-8). During peak glacial periods, radiogenic εNd-values of ~-2.5 to -3.5 are recorded. This confirms a predominance of glacial Pacific-sourced deep water at depths of 3.3-3.6 km in the South Atlantic, with proportions close to 100% and lacking AABW. We advocate for the presence of Pacific Deep Water even during interglacials and further hypothesize that a possible intrusion due to a warming climate could accelerate climate warming. The persistent occurrence of such a highly radiogenic water mass substantially changes the view regarding the selection of the Southern Hemisphere εNd-endmember for the Atlantic Ocean and reinforces the major importance of carbon storage in the Glacial SO.