Constraining the Variability of the Atlantic Meridional Overturning Circulation During the Holocene

Jörg Lippold,Marcus Gutjahr,Tyler J Goepfert,Jasmin M Link,Stefan Rheinberger,Frerk Pöppelmeier,Lukas Wacker,Patrick Blaser,Finn Süfke,Samuel L Jaccard,Oliver Friedrich

doi:10.1029/2019gl084988

Abstract

AbstractThere 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.

Highlights

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
The generally constant baseline during the Holocene suggests attenuated natural variability of the large‐scale Atlantic Meridional Overturning Circulation (AMOC) on submillennial timescales and calls for compensating effects involving the upstream components of North Atlantic Deep Water
Atlantic Meridional Overturning Circulation (AMOC) variability has been linked to changes in the formation rate of North Atlantic Deep Water (NADW)

Summary

Introduction

Atlantic Meridional Overturning Circulation (AMOC) variability has been linked to changes in the formation rate of North Atlantic Deep Water (NADW). Painstaking efforts have been devoted to reconstruct changes in AMOC dynamics in the recent geological past in order to better predict its future evolution. These investigations provide ample evidence for large‐scale glacial and deglacial AMOC reorganizations as inferred from independent proxy approaches (Howe, Piotrowski, Noble, et al, 2016; Lippold et al, 2016; Lynch‐Stieglitz, 2017; Marchitto & Broecker, 2006; McManus et al, 1999; Oppo et al, 2018; Praetorius et al, 2008; Roberts et al, 2010). Discrepancies remain regarding the timing, overall tendency, and amplitude of deep water export variations based on a wealth of various proxy records, mainly focusing on upstream tributaries of NADW including the Labrador Sea Water (LSW) and Nordic Seas Overflow Waters (Ellison et al, 2006; Hall et al, 2004; Hoogakker et al, 2011; Keigwin et al, 2005; Kissel et al, 2013; Kleiven et al, 2008; Mjell et al, 2015; Moffa‐Sánchez & Hall, 2017; Thornalley et al, 2013)

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