Early deglacial CO2 release from the Sub-Antarctic Atlantic and Pacific oceans

Over the last deglaciation there were two transient intervals of pronounced atmospheric CO2 rise; Heinrich Stadial 1 (17.5-15 kyr) and the Younger Dryas (12.9-11.5 kyr). Leading hypotheses accounting for the increased accumulation of CO2 in the atmosphere at these times invoke deep ocean carbon being released from the Southern Ocean and an associated decline in the global efficiency of the biological carbon pump. Here we present new deglacial surface seawater pH and CO2sw records from the Sub-Antarctic regions of the Atlantic and Pacific oceans using boron isotopes measured on the planktic foraminifera Globigerina bulloides. These new data support the hypothesis that upwelling of carbon-rich water in the Sub-Antarctic occurred during Heinrich Stadial 1, and contributed to the initial increase in atmospheric CO2. The increase in CO2sw is coeval with a decline in biological productivity at both the Sub-Antarctic Atlantic and Pacific sites. However, there is no evidence for a significant outgassing of deep ocean carbon from the Sub-Antarctic during the rest of the deglacial, including the second period of atmospheric CO2 rise coeval with the Younger Dryas. This suggests that the second rapid increase in atmospheric CO2 is driven by processes operating elsewhere in the Southern Ocean, or another region.

CO flux, Heinrich Stadial 1, Southern Ocean, Sub-Antarctic, boron isotopes, deglaciation

10.1016/j.epsl.2020.116649

0012-821X

Shuttleworth, R.

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Bostock, H.C.

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Chalk, T.B.

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Calvo, E.

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Jaccard, S.L.

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Pelejero, C.

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Garcia Martinez, A.

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Foster, G.

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15 January 2021

Shuttleworth, R.

975a2765-3771-4152-b352-46956135f4b0

Bostock, H.C.

a2c12519-6e77-4663-aeb3-37383b10b36f

Chalk, T.B.

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Calvo, E.

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Jaccard, S.L.

2ca25b07-e88d-442b-b655-c05fd1f1f79b

Pelejero, C.

c62922ff-6e29-4486-ae8c-7027c01ab71e

Garcia Martinez, A.

aa37bfc1-1546-4f75-a2c8-16b8d93b7ecc

Foster, G.

fbaa7255-7267-4443-a55e-e2a791213022

Shuttleworth, R., Bostock, H.C., Chalk, T.B., Calvo, E., Jaccard, S.L., Pelejero, C., Garcia Martinez, A. and Foster, G. (2021) Early deglacial CO2 release from the Sub-Antarctic Atlantic and Pacific oceans. Earth and Planetary Science Letters, 554, [116649]. (doi:10.1016/j.epsl.2020.116649).

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Shuttleworth et al. Sub Antarctic Deglacial CO2 Release Manuscript - Accepted Manuscript

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Accepted/In Press date: 26 October 2020

Published date: 15 January 2021

Additional Information: Funding Information: We would like to thank the captains, crew and scientists that were involved in collecting the cores used in this study, specifically captain Doug Monks and the crew of the RV Tangaroa who helped collect the TAN1106-28 core. The funding for the TAN1106 voyage was from the Coasts and Oceans Physical Resources program awarded to the National Institute of Water and Atmospheric Research, New Zealand (grant number COPR1703). We thank Bryn Taiapa and Geraldine Jacobsen (ANSTO) for additional radiocarbon data for core TAN1106-28, this work was funded by AINSE grant number ALNGRA15502 and Dr Samuel Toucanne (Ifremer) for providing a further radiocarbon date to improve the age modelling of the deglaciation. We also thank Andy Milton, Matt Cooper, and Megan Spencer as well as the rest of the Foster lab for laboratory assistance. This project was supported by the Natural Environment Research Council [NE/L002531/1] to R.S. and [NE/J021075/1] to G.L.F. Spanish Ministry of Science and Innovation [CGL2015-68194-R] to E.C. and C.P. S.L.J. acknowledges financial support from the Swiss National Science Foundation (SNSF grant PP00P2_172915), and A.M.-G. acknowledges funding from the Max Planck Society. Funding Information: We would like to thank the captains, crew and scientists that were involved in collecting the cores used in this study, specifically captain Doug Monks and the crew of the RV Tangaroa who helped collect the TAN1106-28 core. The funding for the TAN1106 voyage was from the Coasts and Oceans Physical Resources program awarded to the National Institute of Water and Atmospheric Research , New Zealand (grant number COPR1703 ). We thank Bryn Taiapa and Geraldine Jacobsen (ANSTO) for additional radiocarbon data for core TAN1106-28, this work was funded by AINSE grant number ALNGRA15502 and Dr Samuel Toucanne (Ifremer) for providing a further radiocarbon date to improve the age modelling of the deglaciation. We also thank Andy Milton, Matt Cooper, and Megan Spencer as well as the rest of the Foster lab for laboratory assistance. This project was supported by the Natural Environment Research Council [ NE/L002531/1 ] to R.S. and [ NE/J021075/1 ] to G.L.F., Spanish Ministry of Science and Innovation [ CGL2015-68194-R ] to E.C. and C.P., S.L.J. acknowledges financial support from the Swiss National Science Foundation (SNSF grant PP00P2_172915 ), and A.M.-G. acknowledges funding from the Max Planck Society . Publisher Copyright: © 2020 Elsevier B.V.

Keywords: CO flux, Heinrich Stadial 1, Southern Ocean, Sub-Antarctic, boron isotopes, deglaciation

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