Northern source for Deglacial and Holocene deepwater composition changes in the Eastern North Atlantic Basin

Repschlaeger, Janne, Weinelt, Mara, Andersen, Nils, Garbe-Schönberg, Dieter and Schneider, Ralph (2015) Northern source for Deglacial and Holocene deepwater composition changes in the Eastern North Atlantic Basin Earth and Planetary Science Letters, 425 . pp. 256-267.

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Abstract

Over the last decades extensive research has been carried out on changes in the Atlantic Meridional Overturning Circulation and its role during the last deglacial period. At present, only a few high-resolution data sets from the deep eastern North Atlantic exist for this period. It therefore remains uncertain whether deepwater changes in the Eastern North Atlantic Basin were governed by alternating contributions of northern and southern deepwater or whether the Eastern North Atlantic Basin reflects changes in the initial composition and source of North Atlantic deepwater. Furthermore, it is still debated whether such changes are triggered by Northern or Southern Hemisphere climatic changes. In this centennial to decadal scale resolution study we investigate deepwater composition changes in the Eastern North Atlantic Basin over the last 15 ka BR We used sediment cores GEOFAR KF16 and MD08-3180 (37.984 degrees N; 31.118 degrees W, wd 3050 m/37.999 degrees N; 31.134 degrees W, wd 3064 m), obtained from a small basin at the eastern flank of the Mid Atlantic Ridge south of the Azores Islands. Under modern conditions the coring site is situated at the boundary between southern Lower Deep Water and northern Eastern North Atlantic Deep Water consisting of Iceland Scotland Overflow Water and Labrador Sea Water. Distinct differences between the three water masses in terms of ventilation state, temperature and salinity signatures are ideal for tracking changes in the deglacial North Atlantic deepwater distribution using paired benthic foraminiferal stable isotopes (delta C-13, delta O-18) and Mg/Ca bottom water temperature reconstructions. The results show a close coupling of low bottom water temperature (1.5 degrees C) and delta C-13 (0-0.5 parts per thousand) values during cold Heinrich event 1, the Younger Dryas and the Preboreal, that were coeval with a major delta O-18 depletion of deepwater. The strong similarities between subtropical Eastern North Atlantic Deep Water and subpolar North Atlantic surface and deepwater changes indicate that deglacial changes in Eastern North Atlantic Deep Water distribution were triggered in the North Atlantic. Consequently, this would imply that changes in the North Atlantic also contributed to deglacial changes in Antarctic bottom water composition. During the early Holocene stepwise increasing delta C-13 values suggest increasing Eastern North Atlantic Deep Water production and/or increasing Eastern North Atlantic Deep Water ventilation with minor but distinct interruptions (at 10.8, 10.6, 9.1, 8.4, 8.1 and 7.2 ka BP), which were most probably also triggered in the subpolar North Atlantic. (C) 2015 Elsevier B.V. All rights reserved.

Document Type: Article
Additional Information: Times Cited: 1
Research affiliation: Kiel University > Faculty of Mathematics and Natural Sciences > Institute of Geosciences
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University > Other > Leibniz-Laboratory for Radiometric Dating and Isotope Research
Refereed: Yes
ISSN: 0012-821X
Projects: Future Ocean
Date Deposited: 18 Oct 2016 03:46
Last Modified: 27 Feb 2017 15:18
URI: http://eprints.uni-kiel.de/id/eprint/32654

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