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Geochemical response of the mid-depth Northeast Atlantic Ocean to freshwater input during Heinrich events 1 to 4

Geochemical response of the mid-depth Northeast Atlantic Ocean to freshwater input during Heinrich events 1 to 4
Geochemical response of the mid-depth Northeast Atlantic Ocean to freshwater input during Heinrich events 1 to 4
Heinrich events are intervals of rapid iceberg-sourced freshwater release to the high latitude North Atlantic Ocean that punctuate late Pleistocene glacials. Delivery of fresh water to the main North Atlantic sites of deep water formation during Heinrich events may result in major disruption to the Atlantic Meridional Overturning Circulation (AMOC), however, the simple concept of an AMOC shutdown in response to each freshwater input has recently been shown to be overly simplistic. Here we present a new multi-proxy dataset spanning the last 41,000 years that resolves four Heinrich events at a classic mid-depth North Atlantic drill site, employing four independent geochemical tracers of water mass properties: boron/calcium, carbon and oxygen isotopes in foraminiferal calcite and neodymium isotopes in multiple substrates. We also report rare earth element distributions to investigate the fidelity by which neodymium isotopes record changes in water mass distribution in the northeast North Atlantic. Our data reveal distinct geochemical signatures for each Heinrich event, suggesting that the sites of fresh water delivery and/or rates of input played at least as important a role as the stage of the glacial cycle in which the fresh water was released. At no time during the last 41 kyr was the mid-depth northeast North Atlantic dominantly ventilated by southern-sourced water. Instead, we document persistent ventilation by Glacial North Atlantic Intermediate Water (GNAIW), albeit with variable properties signifying changes in supply from multiple contributing northern sources.
Heinrich events, North Atlantic palaeoceanography, Last glacial period, Neodymium isotopes, B/Ca, Carbon and oxygen isotopes, Ice-rafted debris, ODP Site 980
0277-3791
236-254
Crocker, Anya J.
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Chalk, Thomas B.
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Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Spencer, Megan R.
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Gutjahr, Marcus
5babbbc4-2a1a-48df-a2e3-d87b2483ea9c
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Crocker, Anya J.
1215fbdd-ad43-408a-bd79-c54c6847e68c
Chalk, Thomas B.
0021bbe6-6ab1-4a30-8542-654d0f2d1a0a
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Spencer, Megan R.
15e775ce-fdea-4050-8ec8-e701029fccd7
Gutjahr, Marcus
5babbbc4-2a1a-48df-a2e3-d87b2483ea9c
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Crocker, Anya J., Chalk, Thomas B., Bailey, Ian, Spencer, Megan R., Gutjahr, Marcus, Foster, Gavin L. and Wilson, Paul A. (2016) Geochemical response of the mid-depth Northeast Atlantic Ocean to freshwater input during Heinrich events 1 to 4. Quaternary Science Reviews, 151, 236-254. (doi:10.1016/j.quascirev.2016.08.035).

Record type: Article

Abstract

Heinrich events are intervals of rapid iceberg-sourced freshwater release to the high latitude North Atlantic Ocean that punctuate late Pleistocene glacials. Delivery of fresh water to the main North Atlantic sites of deep water formation during Heinrich events may result in major disruption to the Atlantic Meridional Overturning Circulation (AMOC), however, the simple concept of an AMOC shutdown in response to each freshwater input has recently been shown to be overly simplistic. Here we present a new multi-proxy dataset spanning the last 41,000 years that resolves four Heinrich events at a classic mid-depth North Atlantic drill site, employing four independent geochemical tracers of water mass properties: boron/calcium, carbon and oxygen isotopes in foraminiferal calcite and neodymium isotopes in multiple substrates. We also report rare earth element distributions to investigate the fidelity by which neodymium isotopes record changes in water mass distribution in the northeast North Atlantic. Our data reveal distinct geochemical signatures for each Heinrich event, suggesting that the sites of fresh water delivery and/or rates of input played at least as important a role as the stage of the glacial cycle in which the fresh water was released. At no time during the last 41 kyr was the mid-depth northeast North Atlantic dominantly ventilated by southern-sourced water. Instead, we document persistent ventilation by Glacial North Atlantic Intermediate Water (GNAIW), albeit with variable properties signifying changes in supply from multiple contributing northern sources.

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Crocker et al 16 QSR for REF.pdf - Accepted Manuscript
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Accepted/In Press date: 26 August 2016
Published date: 1 November 2016
Keywords: Heinrich events, North Atlantic palaeoceanography, Last glacial period, Neodymium isotopes, B/Ca, Carbon and oxygen isotopes, Ice-rafted debris, ODP Site 980
Organisations: Geochemistry, Paleooceanography & Palaeoclimate

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Local EPrints ID: 401247
URI: https://eprints.soton.ac.uk/id/eprint/401247
ISSN: 0277-3791
PURE UUID: 5083fd1f-9349-4f49-8d8e-e1831adb3fb6
ORCID for Thomas B. Chalk: ORCID iD orcid.org/0000-0002-2880-3847
ORCID for Megan R. Spencer: ORCID iD orcid.org/0000-0003-0063-2238
ORCID for Gavin L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

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Date deposited: 06 Oct 2016 13:17
Last modified: 15 Aug 2019 05:17

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Contributors

Author: Anya J. Crocker
Author: Thomas B. Chalk ORCID iD
Author: Ian Bailey
Author: Marcus Gutjahr
Author: Gavin L. Foster ORCID iD
Author: Paul A. Wilson

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