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Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean

Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean
Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean
The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. Here we use the boron-isotope composition of planktic foraminifera from a sediment core in the western North Pacific to reconstruct pH and dissolved CO2 concentrations from 24,000 to 8,000 years ago. We find that the productivity peak during the Bølling–Allerød warm interval, 14,700 to 12,900 years ago, was associated with a decrease in near-surface pH and an increase in pCO2, and must therefore have been driven by increased supply of nutrient- and CO2-rich waters. In a climate model ensemble (PMIP3), the presence of large ice sheets over North America results in high rates of wind-driven upwelling within the subpolar North Pacific. We suggest that this process, combined with collapse of North Pacific Intermediate Water formation at the onset of the Bølling–Allerød, led to high rates of upwelling of water rich in nutrients and CO2, and supported the peak in productivity. The respiration of this organic matter, along with poor ventilation, probably caused the regional hypoxia. We suggest that CO2 outgassing from the North Pacific helped to maintain high atmospheric CO2 concentrations during the Bølling–Allerød and contributed to the deglacial CO2 rise.
1752-0894
340-344
Gray, William R.
e8115468-3b1a-4f51-9803-95a8af4a0bc8
Rae, James W.B.
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Wills, Robert C.J.
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Shevenell, Amelia E.
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Taylor, Ben
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Burke, Andrea
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Foster, Gavin L.
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Lear, Caroline H.
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Gray, William R.
e8115468-3b1a-4f51-9803-95a8af4a0bc8
Rae, James W.B.
e22c24a8-9049-43a8-997a-c6dc10a3a26e
Wills, Robert C.J.
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Shevenell, Amelia E.
647657ba-5b5b-42e3-b010-d0d0d5e119ba
Taylor, Ben
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Burke, Andrea
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Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Lear, Caroline H.
c0caf74d-ed6c-4b04-b5c8-de8fc794943c

Gray, William R., Rae, James W.B., Wills, Robert C.J., Shevenell, Amelia E., Taylor, Ben, Burke, Andrea, Foster, Gavin L. and Lear, Caroline H. (2018) Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean. Nature Geoscience, 11 (5), 340-344. (doi:10.1038/s41561-018-0108-6).

Record type: Article

Abstract

The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. Here we use the boron-isotope composition of planktic foraminifera from a sediment core in the western North Pacific to reconstruct pH and dissolved CO2 concentrations from 24,000 to 8,000 years ago. We find that the productivity peak during the Bølling–Allerød warm interval, 14,700 to 12,900 years ago, was associated with a decrease in near-surface pH and an increase in pCO2, and must therefore have been driven by increased supply of nutrient- and CO2-rich waters. In a climate model ensemble (PMIP3), the presence of large ice sheets over North America results in high rates of wind-driven upwelling within the subpolar North Pacific. We suggest that this process, combined with collapse of North Pacific Intermediate Water formation at the onset of the Bølling–Allerød, led to high rates of upwelling of water rich in nutrients and CO2, and supported the peak in productivity. The respiration of this organic matter, along with poor ventilation, probably caused the regional hypoxia. We suggest that CO2 outgassing from the North Pacific helped to maintain high atmospheric CO2 concentrations during the Bølling–Allerød and contributed to the deglacial CO2 rise.

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subarcticPac_deglacial_CO2_release_revised3_v2_text_unlinked_figs_accepted_SI - Accepted Manuscript
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Accepted/In Press date: 21 March 2018
e-pub ahead of print date: 23 April 2018

Identifiers

Local EPrints ID: 421156
URI: http://eprints.soton.ac.uk/id/eprint/421156
ISSN: 1752-0894
PURE UUID: 367f1515-1845-4b7e-81ad-e21c41f7150c
ORCID for Gavin L. Foster: ORCID iD orcid.org/0000-0003-3688-9668

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Date deposited: 23 May 2018 16:30
Last modified: 22 Nov 2021 06:25

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Contributors

Author: William R. Gray
Author: James W.B. Rae
Author: Robert C.J. Wills
Author: Amelia E. Shevenell
Author: Ben Taylor
Author: Andrea Burke
Author: Gavin L. Foster ORCID iD
Author: Caroline H. Lear

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