Multiproxy paleoceanographic study from the western Barents Sea reveals dramatic Younger Dryas onset followed by oscillatory warming trend

Magdalena Łącka,Witold Szczuciński,Matthias Forwick,Danuta Michalska,Marek Zajączkowski,Natalia Szymańska,Joanna Pawłowska

doi:10.1038/s41598-020-72747-4

Abstract

The Younger Dryas (YD) is recognized as a cool period that began and ended abruptly during a time of general warming at the end of the last glacial. New multi-proxy data from a sediment gravity core from Storfjordrenna (western Barents Sea, 253 m water depth) reveals that the onset of the YD occurred as a single short-lived dramatic environment deterioration, whereas the subsequent warming was oscillatory. The water masses in the western Barents Sea were likely strongly stratified at the onset of the YD, possibly due to runoff of meltwater combined with perennial sea-ice cover, the latter may last up to several decades without any brake-up. Consequently, anoxic conditions prevailed at the bottom of Storfjordrenna, leading to a sharp reduction of benthic biota and the appearance of vivianite microconcretions which formation is favoured by reducing conditions. While the anoxic conditions in Storfjordrenna were transient, the unfavorable conditions for benthic foraminifera lasted for c. 1300 years. We suggest that the Pre-Boreal Oscillation, just after the onset of the Holocene, may have been a continuation of the oscillatory warming trend during the YD.

Highlights

The Atlantic Meridional Overturning Circulation (AMOC) transports heat and salt northwards throughout the southern and northern Atlantic Ocean
At the very beginning of the Younger Dryas (YD), foraminifera were absent and ice-rafted debris (IRD) flux was low, the latter likely resulting from suppressed iceberg drift due to perennial sea ice[13]
The identification of vivianite was confirmed by X-ray diffraction and semiquantitative geochemical composition analyses using scanning electron microscope energy dispersive spectroscopy

Summary

Introduction

The Atlantic Meridional Overturning Circulation (AMOC) transports heat and salt northwards throughout the southern and northern Atlantic Ocean. Numerous climate predictions using numerical and theoretical models of ocean circulation suggest that the AMOC will weaken over the coming century due to glacial meltwater runoff and decreases in sea ice cover under global warming[1]. As earlier investigations focused mainly on overviews of Late Glacial and Holocene paleoceanography of the Nordic Seas, the YD interval in marine records was presented in low temporal resolution (several hundreds of years). An earlier study of sediment gravity core JM09-020-GC from Storfjordrenna (western Barents Sea; Fig. 1) revealed that the YD was not uniformly cold as had earlier been proposed and that at least some warmer periods occurred[13]. Higher temporal resolution than that presented in Łącka et al.[13] consisting of sedimentological (ice-rafted debris counts), mineralogical (analyses of vivianite), micropaleontological (benthic foraminifera counts) and geochemical (Mn/Fe, oxygen stable isotopes, composition of microconcretions) analyses and we compare our results to other paleoclimatic records. The aim of this study is to provide a more detailed understanding of the oceanographic variability that occurred in the western Barents Sea during this stadial

Objectives

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Results

Conclusion