A saltier glacial Mediterranean outflow
A saltier glacial Mediterranean outflow
©2018. American Geophysical Union. The state of Atlantic Meridional Overturning Circulation (AMOC) is influenced by both the strength and the location of the Mediterranean Outflow Water (MOW) plume in the Gulf of Cadiz. To evaluate the influence of MOW on AMOC over deglaciations, precise and accurate salinity and temperature reconstructions are needed. For this purpose, we measured Mg/Ca and clumped isotopes of several benthic foraminiferal species at Integrated Ocean Drilling Program Site U1390 in the Gulf of Cadiz. The clumped isotope results of Cibicidoides pachyderma, Uvigerina mediterranea, and Pyrgo spp. are consistent between species and record no significant difference in Last Glacial Maximum to Holocene deep water temperature. Over the deglaciation, the Mg/Ca-based temperatures derived from U. mediterranea indicate three periods of MOW absence at Site U1390. Mg/Ca-based temperatures of Hoeglundina elegans and C. pachyderma are on average 6°C too cold when compared to the present core-top temperature, which we explain by a carbonate ion effect on these epibenthic species related to the high alkalinity of the MOW. Combining deep water temperature estimates with the benthic oxygen isotope data and considering different relationships between seawater oxygen isotopes and salinity, we infer a salinity decrease of MOW by three to eight units over the deglaciation and four units during Sapropel 1, accounting for the global δ 18 O depletion due to the decrease in ice volume. Our findings confirm that the Mediterranean Sea accumulates excess salt during a glacial low stand and suggest that this salt surged into the Atlantic over the deglaciation, presumably during Heinrich Stadial 1.
Gibraltar buoyancy exchange, Heinrich events, Mediterranean salinity
179-197
van Dijk, J.
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Ziegler, M.
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de Nooijer, L.J.
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Reichart, G.J.
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Xuan, C.
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Ducassou, E.
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Bernasconi, S.M.
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Lourens, L.J.
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February 2018
van Dijk, J.
f05f1de9-1157-4aea-9d15-56be79468946
Ziegler, M.
803ba330-20ad-426a-9f0d-c3164f927812
de Nooijer, L.J.
ff491e03-c179-4239-94a9-e30016f31cba
Reichart, G.J.
dd155475-f861-47d6-9a00-d1a927bb4d08
Xuan, C.
3f3cad12-b17b-46ae-957a-b362def5b837
Ducassou, E.
b92cc04f-1c63-47c6-b1a8-d3ea9d12f1d4
Bernasconi, S.M.
d60685c9-9440-45e1-a27e-9e9e1c872082
Lourens, L.J.
d3c5b95b-b14d-4f5f-8ec1-f3f517335ca1
van Dijk, J., Ziegler, M., de Nooijer, L.J., Reichart, G.J., Xuan, C., Ducassou, E., Bernasconi, S.M. and Lourens, L.J.
(2018)
A saltier glacial Mediterranean outflow.
Paleoceanography and Paleoclimatology, 33 (2), .
(doi:10.1002/2017PA003228).
Abstract
©2018. American Geophysical Union. The state of Atlantic Meridional Overturning Circulation (AMOC) is influenced by both the strength and the location of the Mediterranean Outflow Water (MOW) plume in the Gulf of Cadiz. To evaluate the influence of MOW on AMOC over deglaciations, precise and accurate salinity and temperature reconstructions are needed. For this purpose, we measured Mg/Ca and clumped isotopes of several benthic foraminiferal species at Integrated Ocean Drilling Program Site U1390 in the Gulf of Cadiz. The clumped isotope results of Cibicidoides pachyderma, Uvigerina mediterranea, and Pyrgo spp. are consistent between species and record no significant difference in Last Glacial Maximum to Holocene deep water temperature. Over the deglaciation, the Mg/Ca-based temperatures derived from U. mediterranea indicate three periods of MOW absence at Site U1390. Mg/Ca-based temperatures of Hoeglundina elegans and C. pachyderma are on average 6°C too cold when compared to the present core-top temperature, which we explain by a carbonate ion effect on these epibenthic species related to the high alkalinity of the MOW. Combining deep water temperature estimates with the benthic oxygen isotope data and considering different relationships between seawater oxygen isotopes and salinity, we infer a salinity decrease of MOW by three to eight units over the deglaciation and four units during Sapropel 1, accounting for the global δ 18 O depletion due to the decrease in ice volume. Our findings confirm that the Mediterranean Sea accumulates excess salt during a glacial low stand and suggest that this salt surged into the Atlantic over the deglaciation, presumably during Heinrich Stadial 1.
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Accepted/In Press date: 1 January 2018
e-pub ahead of print date: 10 February 2018
Published date: February 2018
Keywords:
Gibraltar buoyancy exchange, Heinrich events, Mediterranean salinity
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Local EPrints ID: 418705
URI: http://eprints.soton.ac.uk/id/eprint/418705
PURE UUID: 69cd1d35-5e0d-4199-a854-8c59d4bd61a1
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Date deposited: 19 Mar 2018 17:30
Last modified: 16 Apr 2024 04:01
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Contributors
Author:
J. van Dijk
Author:
M. Ziegler
Author:
L.J. de Nooijer
Author:
G.J. Reichart
Author:
E. Ducassou
Author:
S.M. Bernasconi
Author:
L.J. Lourens
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