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On climate and abyssal circulation in the Atlantic Ocean during late Pliocene marine isotope stage M2, ∼3.3 million years ago

On climate and abyssal circulation in the Atlantic Ocean during late Pliocene marine isotope stage M2, ∼3.3 million years ago
On climate and abyssal circulation in the Atlantic Ocean during late Pliocene marine isotope stage M2, ∼3.3 million years ago

Marine Isotope Stage (MIS) M2, 3.3 Ma, is an isolated cold stage punctuating the benthic oxygen isotope (δ 18O) stratigraphy of the warm Piacenzian interval of the late Pliocene Epoch. The prominent (∼0.65‰) δ 18O increase that defines MIS M2 has prompted debate over the extent to which it signals an early prelude to the rhythmic extensive glaciations of the northern hemisphere that characterise the Quaternary and raised questions about the forcing mechanisms responsible. Recent work suggests that CO 2 storage in the deep Atlantic Ocean played an important role in these events but detailed reconstructions of deep ocean chemical stratification are needed to test this idea and competing hypotheses. Here we present new records of the Nd isotope composition of fish debris and δ 13C and B/Ca ratios of benthic foraminifera from the northwest and southeast Atlantic Ocean. Our novel geochemical data show that, in contrast to major Quaternary glaciations such as MIS 2 (∼21 ka) and MIS 100 (∼2.52 Ma), the deep North Atlantic Ocean was weakly chemically stratified during MIS M2. We show that Southern Component Water incursion into the Atlantic Ocean was limited to the deep South Atlantic basin during MIS M2 and peaked well before (∼10-15-kyr) the atmospheric CO 2 minimum. Our findings imply that the deep Atlantic Ocean was not the principle sink of CO 2 sequestered from the atmosphere during MIS M2, implicating a different CO 2 storage deep-water reservoir mechanism, presumably Southern Component Water incursion into the Pacific Ocean. Weak chemical stratification in the deep Atlantic Ocean during MIS M2 relative to MIS 100 and 2 suggests comparatively active Atlantic meridional overturning circulation. That suggestion is consistent with the warmth of the high latitude North Atlantic during MIS M2 – surface water temperatures cooled during M2 but only close to Holocene values. Our findings may help to explain the paucity of evidence for extensive early glaciation of the northern hemisphere during M2 but leave open the possibility of ice sheet advance on Antarctica.

AABW, AMOC, Atlantic circulation, Last glacial, MIS 100, MIS M2, NADW
0277-3791
Kirby, Nicola
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Bailey, Ian
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Lang, David C.
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Brombacher, Anieke
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Chalk, Thomas B.
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Parker, Rebecca L.
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Crocker, Anya J.
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Taylor, Victoria E.
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Milton, James A.
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Foster, Gavin L.
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Raymo, Maureen E.
eda6af85-8c8a-40d8-8777-a262b1e03ab4
Kroon, Dick
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Bell, David B.
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Wilson, Paul A.
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Kirby, Nicola
1e007e60-389e-4334-889b-c42ba855c83b
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Lang, David C.
930ac2ed-a575-419f-af64-a7965a161638
Brombacher, Anieke
2a4bbb84-4743-4a36-973b-4ad2bf743154
Chalk, Thomas B.
b8efb41d-0365-43fe-b98b-272f8b755f3f
Parker, Rebecca L.
88389e23-2b38-4b92-b7c4-43556a3a7a66
Crocker, Anya J.
49f1d398-25e9-4729-9ef9-f477c8fb122f
Taylor, Victoria E.
b6b7825e-b779-4dc7-b58e-cad8a87a0752
Milton, James A.
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Raymo, Maureen E.
eda6af85-8c8a-40d8-8777-a262b1e03ab4
Kroon, Dick
0b73c1aa-21fe-4d70-b46e-2a8e8a84abc7
Bell, David B.
d33b8fe2-a171-4593-b68d-59380fc77b4f
Wilson, Paul A.
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Kirby, Nicola, Bailey, Ian, Lang, David C., Brombacher, Anieke, Chalk, Thomas B., Parker, Rebecca L., Crocker, Anya J., Taylor, Victoria E., Milton, James A., Foster, Gavin L., Raymo, Maureen E., Kroon, Dick, Bell, David B. and Wilson, Paul A. (2020) On climate and abyssal circulation in the Atlantic Ocean during late Pliocene marine isotope stage M2, ∼3.3 million years ago. Quaternary Science Reviews, 250, [106644]. (doi:10.1016/j.quascirev.2020.106644).

Record type: Article

Abstract

Marine Isotope Stage (MIS) M2, 3.3 Ma, is an isolated cold stage punctuating the benthic oxygen isotope (δ 18O) stratigraphy of the warm Piacenzian interval of the late Pliocene Epoch. The prominent (∼0.65‰) δ 18O increase that defines MIS M2 has prompted debate over the extent to which it signals an early prelude to the rhythmic extensive glaciations of the northern hemisphere that characterise the Quaternary and raised questions about the forcing mechanisms responsible. Recent work suggests that CO 2 storage in the deep Atlantic Ocean played an important role in these events but detailed reconstructions of deep ocean chemical stratification are needed to test this idea and competing hypotheses. Here we present new records of the Nd isotope composition of fish debris and δ 13C and B/Ca ratios of benthic foraminifera from the northwest and southeast Atlantic Ocean. Our novel geochemical data show that, in contrast to major Quaternary glaciations such as MIS 2 (∼21 ka) and MIS 100 (∼2.52 Ma), the deep North Atlantic Ocean was weakly chemically stratified during MIS M2. We show that Southern Component Water incursion into the Atlantic Ocean was limited to the deep South Atlantic basin during MIS M2 and peaked well before (∼10-15-kyr) the atmospheric CO 2 minimum. Our findings imply that the deep Atlantic Ocean was not the principle sink of CO 2 sequestered from the atmosphere during MIS M2, implicating a different CO 2 storage deep-water reservoir mechanism, presumably Southern Component Water incursion into the Pacific Ocean. Weak chemical stratification in the deep Atlantic Ocean during MIS M2 relative to MIS 100 and 2 suggests comparatively active Atlantic meridional overturning circulation. That suggestion is consistent with the warmth of the high latitude North Atlantic during MIS M2 – surface water temperatures cooled during M2 but only close to Holocene values. Our findings may help to explain the paucity of evidence for extensive early glaciation of the northern hemisphere during M2 but leave open the possibility of ice sheet advance on Antarctica.

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Kirby et al. accepted QSR - Accepted Manuscript
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e-pub ahead of print date: 9 October 2020
Published date: 15 December 2020
Keywords: AABW, AMOC, Atlantic circulation, Last glacial, MIS 100, MIS M2, NADW

Identifiers

Local EPrints ID: 448953
URI: http://eprints.soton.ac.uk/id/eprint/448953
ISSN: 0277-3791
PURE UUID: 15452da4-427f-4c77-aa7d-69e733aa2f50
ORCID for Anieke Brombacher: ORCID iD orcid.org/0000-0003-2310-047X
ORCID for Victoria E. Taylor: ORCID iD orcid.org/0000-0002-6909-1575
ORCID for Gavin L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

Catalogue record

Date deposited: 11 May 2021 17:11
Last modified: 26 Nov 2021 06:36

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Contributors

Author: Nicola Kirby
Author: Ian Bailey
Author: David C. Lang
Author: Thomas B. Chalk
Author: Rebecca L. Parker
Author: Anya J. Crocker
Author: James A. Milton
Author: Gavin L. Foster ORCID iD
Author: Maureen E. Raymo
Author: Dick Kroon
Author: David B. Bell
Author: Paul A. Wilson

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