Reconstructing deglacial North and South Atlantic deep water sourcing using foraminiferal Nd isotopes

Piotrowski, A. M. and Galy, A. and Nicholl, J. A. L. and Roberts, N. and Wilson, D. J. and Clegg, J. A. and Yu, J. (2012) Reconstructing deglacial North and South Atlantic deep water sourcing using foraminiferal Nd isotopes. Earth and Planetary Science Letters, 357–35. pp. 289-297. ISSN 0012-821X DOI 10.1016/j.epsl.2012.09.036

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Abstract

During the last few decades, neodymium isotopes have been increasingly used as a paleoceanographic and paleoclimate proxy on million-year through millennial time-scales. The widespread use of the Nd isotope proxy depends on whether the Nd isotopic composition of past seawater can be reliably extracted from authigenic sediment phases. Here we show evidence that planktonic foraminifera with authigenic coatings preserve a deep water Nd isotopic signature and thus can be used to reconstruct past deep water Nd isotopes. Applying this method downcore on South Atlantic Deep Cape Basin core TNO57-21 (41.1°S, 7.9°E, 4981 m), the Nd isotopic composition of the planktonic foraminiferal Fe–Mn oxide coatings is identical with and confirms that of the reductively leached bulk sediment fraction (Piotrowski et al., 2004, 2005, 2008) as reflecting changes in bottom water sourcing. In the case of northeastern North Atlantic core BOFS 8K (52.5°N 22.1°W, 4045 m), the planktonic foraminiferal Fe–Mn oxide coatings have different Nd isotopes from reductive sediment leaches. Clearly acid-reductive leaching must be tested in more detail. We observe that the Nd isotopic composition of the deep northeastern Atlantic core shifted during the deglaciation, from glacial values similar to the South Atlantic Cape Basin towards Holocene values similar to the Bermuda Rise (Roberts et al., 2010). Taken as a whole, the Nd isotope record from foraminiferal authigenic coatings suggests large-scale changes in the proportion of northern and southern deep water sources occurred throughout the Atlantic Ocean, with substantial chemical gradients at times, during the last deglaciation.

Item Type: Article
Uncontrolled Keywords: 2012AREP; IA64;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 357–35
Page Range: pp. 289-297
Identification Number: 10.1016/j.epsl.2012.09.036
Depositing User: Sarah Humbert
Date Deposited: 29 Oct 2012 17:24
Last Modified: 23 Jul 2013 10:04
URI: http://eprints.esc.cam.ac.uk/id/eprint/2609

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