Middle Holocene expansion of Pacific Deep Water into the Southern Ocean

The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulatio...

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Published in:Proceedings of the National Academy of Sciences
Main Authors: Struve, T, Wilson, DJ, Van de Flierdt, T, Pratt, N, Crocket, KC
Other Authors: Natural Environment Research Council (NERC), Commission of the European Communities, The Leverhulme Trust
Format: Article in Journal/Newspaper
Language:English
Published: Proceedings of the National Academy of Sciences 2019
Subjects:
Online Access:http://hdl.handle.net/10044/1/76625
https://doi.org/10.1073/pnas.1908138117
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spelling ftimperialcol:oai:spiral.imperial.ac.uk:10044/1/76625 2023-05-15T18:24:04+02:00 Middle Holocene expansion of Pacific Deep Water into the Southern Ocean Struve, T Wilson, DJ Van de Flierdt, T Pratt, N Crocket, KC Natural Environment Research Council (NERC) Commission of the European Communities The Leverhulme Trust 2019-12-01 http://hdl.handle.net/10044/1/76625 https://doi.org/10.1073/pnas.1908138117 en eng Proceedings of the National Academy of Sciences Proceedings of the National Academy of Sciences 0027-8424 http://hdl.handle.net/10044/1/76625 doi:10.1073/pnas.1908138117 NE/F016751/1 PIRG03-GA-2008-230828 RPG-398 NE/N001141/1 © 2020 Published under the PNAS license (https://www.pnas.org/site/aboutpnas/licenses.xhtml). 894 889 Journal Article 2019 ftimperialcol https://doi.org/10.1073/pnas.1908138117 2020-02-13T23:38:12Z The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulation and mixing of water masses in this important location. While changes in SWW forcing during the Holocene (i.e., the last ∼11,700 y) have been documented, evidence of the oceanic response to these changes is equivocal. Here we use the neodymium (Nd) isotopic composition of absolute-dated cold-water coral skeletons to show that there have been distinct changes in the chemistry of the Southern Ocean water column during the Holocene. Our results reveal a pronounced Middle Holocene excursion (peaking ∼7,000–6,000 y before present), at the depth level presently occupied by Upper Circumpolar Deep Water (UCDW), toward Nd isotope values more typical of Pacific waters. We suggest that poleward-reduced SWW forcing during the Middle Holocene led to both reduced Southern Ocean deep mixing and enhanced influx of Pacific Deep Water into UCDW, inducing a water mass structure that was significantly different from today. Poleward SWW intensification during the Late Holocene could then have reinforced deep mixing along and across density surfaces, thus enhancing the release of accumulated CO2 to the atmosphere. Article in Journal/Newspaper Southern Ocean Imperial College London: Spiral Pacific Southern Ocean Proceedings of the National Academy of Sciences 117 2 889 894
institution Open Polar
collection Imperial College London: Spiral
op_collection_id ftimperialcol
language English
description The Southern Ocean is a key region for the overturning and mixing of water masses within the global ocean circulation system. Because Southern Ocean dynamics are influenced by the Southern Hemisphere westerly winds (SWW), changes in the westerly wind forcing could significantly affect the circulation and mixing of water masses in this important location. While changes in SWW forcing during the Holocene (i.e., the last ∼11,700 y) have been documented, evidence of the oceanic response to these changes is equivocal. Here we use the neodymium (Nd) isotopic composition of absolute-dated cold-water coral skeletons to show that there have been distinct changes in the chemistry of the Southern Ocean water column during the Holocene. Our results reveal a pronounced Middle Holocene excursion (peaking ∼7,000–6,000 y before present), at the depth level presently occupied by Upper Circumpolar Deep Water (UCDW), toward Nd isotope values more typical of Pacific waters. We suggest that poleward-reduced SWW forcing during the Middle Holocene led to both reduced Southern Ocean deep mixing and enhanced influx of Pacific Deep Water into UCDW, inducing a water mass structure that was significantly different from today. Poleward SWW intensification during the Late Holocene could then have reinforced deep mixing along and across density surfaces, thus enhancing the release of accumulated CO2 to the atmosphere.
author2 Natural Environment Research Council (NERC)
Commission of the European Communities
The Leverhulme Trust
format Article in Journal/Newspaper
author Struve, T
Wilson, DJ
Van de Flierdt, T
Pratt, N
Crocket, KC
spellingShingle Struve, T
Wilson, DJ
Van de Flierdt, T
Pratt, N
Crocket, KC
Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
author_facet Struve, T
Wilson, DJ
Van de Flierdt, T
Pratt, N
Crocket, KC
author_sort Struve, T
title Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
title_short Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
title_full Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
title_fullStr Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
title_full_unstemmed Middle Holocene expansion of Pacific Deep Water into the Southern Ocean
title_sort middle holocene expansion of pacific deep water into the southern ocean
publisher Proceedings of the National Academy of Sciences
publishDate 2019
url http://hdl.handle.net/10044/1/76625
https://doi.org/10.1073/pnas.1908138117
geographic Pacific
Southern Ocean
geographic_facet Pacific
Southern Ocean
genre Southern Ocean
genre_facet Southern Ocean
op_source 894
889
op_relation Proceedings of the National Academy of Sciences
0027-8424
http://hdl.handle.net/10044/1/76625
doi:10.1073/pnas.1908138117
NE/F016751/1
PIRG03-GA-2008-230828
RPG-398
NE/N001141/1
op_rights © 2020 Published under the PNAS license (https://www.pnas.org/site/aboutpnas/licenses.xhtml).
op_doi https://doi.org/10.1073/pnas.1908138117
container_title Proceedings of the National Academy of Sciences
container_volume 117
container_issue 2
container_start_page 889
op_container_end_page 894
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