Patrick Blaser, Jörg Lippold, Claire Waelbroeck, David J. Thornalley, Frerk Pöppelmeier, Stefanie Kaboth-Bahr, Janne Repschläger, Samuel L. Jaccard

Changes in the configuration and properties of deep ocean water masses modulated Quaternary climate transitions between ice ages and interglacials. For example, it is thought that North Atlantic Deep Water (NADW) was volumetrically reduced during the last glacial period. Yet, reconstructions based on individual types of proxy observations yield diverging results about the past spatial extent and properties of NADW.
Here we combine observations from five different proxies for the reconstruction of Atlantic source water distributions during the Last Glacial Maximum and Heinrich Stadial 1 (23.0 – 14.6 thousand years before present). We find evidence that NADW prevailed in a similar manner as today, albeit both upper and lower NADW existed in two distinct source water modes each, one cold and well ventilated and another less ventilated and possibly warmer.
The inclusion of all four glacial NADW components in estimations of Atlantic deep water
provenance suggest that NADW was prevalent during both time periods, even though significant freshwater fluxes presumably perturbed NADW formation during Heinrich Stadial 1. We hence suggest that NADW during the last glacial was surprisingly prevalent and resilient to disturbance on millennial time scales, which is important for our understanding of the Atlantic overturning circulation.