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Climate-induced variability in Mediterranean outflow to the North Atlantic Ocean during the late Pleistocene

Climate-induced variability in Mediterranean outflow to the North Atlantic Ocean during the late Pleistocene
Climate-induced variability in Mediterranean outflow to the North Atlantic Ocean during the late Pleistocene
Mediterranean Outflow Water (MOW) adds salt and density to open ocean intermediate waters and is therefore an important motor of Atlantic meridional overturning circulation (AMOC) and climate variability. However, the variability in strength and depth of MOW on geological timescales is poorly documented. Here we present new detailed records, with excellent age control, of MOW variability from 416 ka to present from rapidly accumulated marine sediments recovered from the West Iberian Margin during Integrated Ocean Drilling Program (IODP) Expedition 339. Our records of x-ray fluorescence (XRF), physical grain size and palaeocurrent information from the anisotropy of magnetic susceptibility (AMS) indicate (i) a close relationship between the orientation of principle AMS axes and glacial-interglacial cycles and (ii) two distinct regimes of MOW behaviour over the last ~416 kyrs in grain size and AMS variability at orbital (mainly precessional) and suborbital timescales. Between marine isotope stages (MIS) 10 and MIS 4, MOW was focused at a generally shallow depth on the West Iberian Margin, and changes in MOW strength were strongly paced by precession. A transition interval occurred during MIS 5 and 4, when MOW deepened and millennial-scale variability in strength flow strength was superimposed on orbitally paced change. During MIS 11 and from MIS 3 to present, MOW was deeply focused and millennial-scale variability dominated. We infer that late Pleistocene variability in MOW strength and depth were strongly climate- influenced and that changes in circum-Mediterranean rainfall climate were likely a primary control.
2572-4525
Nichols, Matthew
5acc6e34-770c-4f9a-8016-e73f3e1b8363
Xuan, Chuang
3f3cad12-b17b-46ae-957a-b362def5b837
Crowhurst, Simon
386e0ab1-a26d-430d-9229-c049d0c84006
Hodell, David A.
c9977ae9-d52c-4d74-8f01-08391ec61066
Richter, Carl
9e605d8a-fea5-49ee-9193-ee8ea3dccca9
Acton, Gary
eb3c996f-b2b0-4845-96db-439f6c275a02
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Nichols, Matthew
5acc6e34-770c-4f9a-8016-e73f3e1b8363
Xuan, Chuang
3f3cad12-b17b-46ae-957a-b362def5b837
Crowhurst, Simon
386e0ab1-a26d-430d-9229-c049d0c84006
Hodell, David A.
c9977ae9-d52c-4d74-8f01-08391ec61066
Richter, Carl
9e605d8a-fea5-49ee-9193-ee8ea3dccca9
Acton, Gary
eb3c996f-b2b0-4845-96db-439f6c275a02
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Nichols, Matthew, Xuan, Chuang, Crowhurst, Simon, Hodell, David A., Richter, Carl, Acton, Gary and Wilson, Paul A. (2020) Climate-induced variability in Mediterranean outflow to the North Atlantic Ocean during the late Pleistocene. Paleoceanography and Paleoclimatology, 35 (9), [e2020PA003947]. (In Press)

Record type: Article

Abstract

Mediterranean Outflow Water (MOW) adds salt and density to open ocean intermediate waters and is therefore an important motor of Atlantic meridional overturning circulation (AMOC) and climate variability. However, the variability in strength and depth of MOW on geological timescales is poorly documented. Here we present new detailed records, with excellent age control, of MOW variability from 416 ka to present from rapidly accumulated marine sediments recovered from the West Iberian Margin during Integrated Ocean Drilling Program (IODP) Expedition 339. Our records of x-ray fluorescence (XRF), physical grain size and palaeocurrent information from the anisotropy of magnetic susceptibility (AMS) indicate (i) a close relationship between the orientation of principle AMS axes and glacial-interglacial cycles and (ii) two distinct regimes of MOW behaviour over the last ~416 kyrs in grain size and AMS variability at orbital (mainly precessional) and suborbital timescales. Between marine isotope stages (MIS) 10 and MIS 4, MOW was focused at a generally shallow depth on the West Iberian Margin, and changes in MOW strength were strongly paced by precession. A transition interval occurred during MIS 5 and 4, when MOW deepened and millennial-scale variability in strength flow strength was superimposed on orbitally paced change. During MIS 11 and from MIS 3 to present, MOW was deeply focused and millennial-scale variability dominated. We infer that late Pleistocene variability in MOW strength and depth were strongly climate- influenced and that changes in circum-Mediterranean rainfall climate were likely a primary control.

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Accepted/In Press date: 18 August 2020

Identifiers

Local EPrints ID: 443243
URI: http://eprints.soton.ac.uk/id/eprint/443243
ISSN: 2572-4525
PURE UUID: 1cb859b4-90e8-4ce5-b5ba-d1d97a6e7d40
ORCID for Chuang Xuan: ORCID iD orcid.org/0000-0003-4043-3073

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Date deposited: 18 Aug 2020 16:32
Last modified: 18 Feb 2021 17:22

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Contributors

Author: Matthew Nichols
Author: Chuang Xuan ORCID iD
Author: Simon Crowhurst
Author: David A. Hodell
Author: Carl Richter
Author: Gary Acton
Author: Paul A. Wilson

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