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Increased deep ocean carbon storage is often invoked as the major sink for lower atmospheric CO2 concentrations during past ice ages. In order to improve the understanding of the changes in ocean dynamics facilitating such increased oceanic carbon storage, we assess the variability of deep water provenance in the Atlantic by reconstructing authigenic Nd isotopes from North Atlantic site U1313 over the past ∼100 kyr. Under consideration of these new constraints for the northern Nd isotope end-member, we find only limited long-term variations in the meridional and intra-basin water-mass gradients suggesting a prevalence of northern-sourced water (NSW) throughout the past 100 kyr. Tentative results suggest that during the glacial period of Marine Isotope Stage 4 NSW proportions even increased by additional ∼15% in the equatorial and Northeast Atlantic, calling into question the notion that cold climates promote the expansion of southern-sourced water.

There is a converging body of evidence supporting a measurable slowdown of the Atlantic Meridional Overturning Circulation (AMOC) as climate warms and Northern Hemisphere ice sheets inexorably shrink. Within this context, we assess the variability of the AMOC during the Holocene based on a marine sediment core retrieved from the deep northwest Atlantic, which sensitively recorded large‐scale deglacial transitions in deep water circulation. While there is a diffuse notion of Holocene variability in Labrador and Nordic Seas overturning, we report a largely invariable deep water circulation for the last ~11,000 years, even during the meltwater pulse associated with the 8.2‐ka event. Sensitivity tests along with high‐resolution 231Pa/230Th data constrain the duration and the magnitude of possible Holocene AMOC variations. The generally constant baseline during the Holocene suggests attenuated natural variability of the large‐scale AMOC on submillennial timescales and calls for compensating effects involving the upstream components of North Atlantic Deep Water.

Global climatic changes during the last Glacial and Deglacial have been related to variations of the Atlantic Meridional Overturning Circulation (AMOC). Here, we present new and refined 231Pa/230Th down‐core profiles extending back to 30 ka BP from the northwestern Atlantic along the Atlantic Deep Western Boundary Current (DWBC), which is the main component of the southward deep backflow of the AMOC. Besides the well‐known Bermuda Rise records, available high‐resolution 231Pa/230Th data in the northwestern Atlantic are still sparse. Our new records along with reconstructions of deep water provenance from Nd isotopes constrain the timing and magnitude of past changes in AMOC from an additional northwestern Atlantic region forming a depth transect between 3000 and 4760 m water depth. Our extended and improved dataset confirms the weakening of the AMOC during deglacial cold spells such as Heinrich Event 1 and the Younger Dryas interrupted by a reinvigoration during the Bølling‐Allerød interstadial as seen in the prominent 231Pa/230Th records from the Bermuda Rise. However, in contrast to the Bermuda Rise records we find a clearly reduced circulation strength during the Last Glacial Maximum in the deep Atlantic.