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North Atlantic midlatitude surface-circulation changes through the Plio-Pleistocene intensification of northern hemisphere glaciation

North Atlantic midlatitude surface-circulation changes through the Plio-Pleistocene intensification of northern hemisphere glaciation
North Atlantic midlatitude surface-circulation changes through the Plio-Pleistocene intensification of northern hemisphere glaciation
The North Atlantic Current (NAC) transports warm salty water to high northern latitudes, with important repercussions for ocean circulation and global climate. A southward displacement of the NAC and Subarctic Front, which separate subpolar and subtropical water masses, is widely suggested for the last glacial maximum (LGM) and may have acted as a positive feedback in glacial expansion at this time. However, the role of the NAC during the intensification of northern hemisphere glaciation (iNHG) ~3.5 to 2.5 Ma, is less clear. Here, we present new records from IODP Site U1313 (41°N) spanning ~2.8‐2.4 Ma to trace the influence of Subarctic Front waters above this mid‐latitude site. We reconstruct surface and permanent pycnocline temperatures and seawater δ18O using paired Mg/Ca‐δ18O measurements on the planktic foraminifers Globigerinoides ruber and Globorotalia crassaformis, and determine abundances of the subpolar foraminifer Neogloboquadrina atlantica. We find that the first significant glacial incursions of Subarctic Front surface waters above Site U1313 did not occur until ~2.6 Ma. At no time during our study interval was (sub) surface reorganisation in the mid‐latitude North Atlantic analogous to the LGM. Our findings suggest that LGM‐like processes sensu stricto cannot be invoked to explain interglacial‐glacial cycle amplification during iNHG. They also imply that increased glacial productivity at Site U1313 during iNHG was not only driven by southward deflections of the Subarctic Front. We suggest nutrient injection from cold‐core eddies and enhanced glacial dust delivery may have played additional roles in increasing export productivity in the mid‐latitude North Atlantic from 2.7 Ma.
2572-4517
1186-1205
Bolton, Clara T.
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Bailey, Ian
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Friedrich, Oliver
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Tachikawa, Kazuyo
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De Garidel-thoron, Thibault
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Vidal, Laurence
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Sonzogni, Corinne
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Marino, Gianluca
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Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Robinson, Marci M.
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Ermini, Magali
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Koch, Mirjam
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Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Bolton, Clara T.
6308b9cd-c2e7-490e-9279-5b89c8ae909c
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Friedrich, Oliver
30dc21d4-6581-4b89-96b1-c11689e85078
Tachikawa, Kazuyo
b8dd7c88-d0a3-4144-9cd5-a625528a6699
De Garidel-thoron, Thibault
adbcc7e0-4fc8-48e6-86f5-5dad26c54822
Vidal, Laurence
6c601b85-3e74-412e-ac17-4ec10bea652d
Sonzogni, Corinne
f4c419ec-e483-4622-8af8-e7fa02278a7f
Marino, Gianluca
40d6f3f2-0905-4c0f-8eb9-6d577b2833bb
Rohling, Eelco J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Robinson, Marci M.
59f40b6d-1f67-4d3a-aadd-aa75393c9237
Ermini, Magali
e36764ba-f15e-4a50-80e4-57483d91d256
Koch, Mirjam
f06d41f6-5ace-46a3-be82-24b864ba4f0b
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Bolton, Clara T., Bailey, Ian, Friedrich, Oliver, Tachikawa, Kazuyo, De Garidel-thoron, Thibault, Vidal, Laurence, Sonzogni, Corinne, Marino, Gianluca, Rohling, Eelco J., Robinson, Marci M., Ermini, Magali, Koch, Mirjam, Cooper, Matthew J. and Wilson, Paul A. (2018) North Atlantic midlatitude surface-circulation changes through the Plio-Pleistocene intensification of northern hemisphere glaciation. Paleoceanography and Paleoclimatology, 33 (11), 1186-1205. (doi:10.1029/2018PA003412).

Record type: Article

Abstract

The North Atlantic Current (NAC) transports warm salty water to high northern latitudes, with important repercussions for ocean circulation and global climate. A southward displacement of the NAC and Subarctic Front, which separate subpolar and subtropical water masses, is widely suggested for the last glacial maximum (LGM) and may have acted as a positive feedback in glacial expansion at this time. However, the role of the NAC during the intensification of northern hemisphere glaciation (iNHG) ~3.5 to 2.5 Ma, is less clear. Here, we present new records from IODP Site U1313 (41°N) spanning ~2.8‐2.4 Ma to trace the influence of Subarctic Front waters above this mid‐latitude site. We reconstruct surface and permanent pycnocline temperatures and seawater δ18O using paired Mg/Ca‐δ18O measurements on the planktic foraminifers Globigerinoides ruber and Globorotalia crassaformis, and determine abundances of the subpolar foraminifer Neogloboquadrina atlantica. We find that the first significant glacial incursions of Subarctic Front surface waters above Site U1313 did not occur until ~2.6 Ma. At no time during our study interval was (sub) surface reorganisation in the mid‐latitude North Atlantic analogous to the LGM. Our findings suggest that LGM‐like processes sensu stricto cannot be invoked to explain interglacial‐glacial cycle amplification during iNHG. They also imply that increased glacial productivity at Site U1313 during iNHG was not only driven by southward deflections of the Subarctic Front. We suggest nutrient injection from cold‐core eddies and enhanced glacial dust delivery may have played additional roles in increasing export productivity in the mid‐latitude North Atlantic from 2.7 Ma.

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Accepted/In Press date: 29 September 2018
e-pub ahead of print date: 29 September 2018

Identifiers

Local EPrints ID: 425365
URI: http://eprints.soton.ac.uk/id/eprint/425365
ISSN: 2572-4517
PURE UUID: 7437a97b-92fe-4177-8f08-0d0780fcebfe
ORCID for Eelco J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158
ORCID for Matthew J. Cooper: ORCID iD orcid.org/0000-0002-2130-2759

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Date deposited: 16 Oct 2018 16:30
Last modified: 17 Dec 2019 05:11

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Contributors

Author: Clara T. Bolton
Author: Ian Bailey
Author: Oliver Friedrich
Author: Kazuyo Tachikawa
Author: Thibault De Garidel-thoron
Author: Laurence Vidal
Author: Corinne Sonzogni
Author: Gianluca Marino
Author: Marci M. Robinson
Author: Magali Ermini
Author: Mirjam Koch
Author: Paul A. Wilson

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