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Carbon dynamics of the Weddell Gyre, Southern Ocean

Carbon dynamics of the Weddell Gyre, Southern Ocean
Carbon dynamics of the Weddell Gyre, Southern Ocean
The accumulation of carbon within the Weddell Gyre, and its exchanges across the gyre boundaries are investigated with three recent full-depth oceanographic sections enclosing this climatically-important region. The combination of carbon measurements with ocean circulation transport estimates from a box inverse analysis reveal that deep water transports associated with Warm Deep Water (WDW) and Weddell Sea Deep Water dominate the gyre's carbon budget, while a dual-cell vertical overturning circulation leads to both upwelling and the delivery of large quantities of carbon to the deep ocean. Historical sea surface pCO2 observations, interpolated using a neural network technique, confirm the net summertime sink of 0.044 to 0.058 ± 0.010 Pg C yr-1 derived from the inversion. However, a wintertime outgassing signal similar in size results in a statistically insignificant annual air-to-sea CO2 flux of 0.002 ± 0.007 Pg C yr-1 (mean 1998-2011) to 0.012 ± 0.024 Pg C yr-1 (mean 2008-2010) to be diagnosed for the Weddell Gyre. A surface layer carbon balance, independently derived from in situ biogeochemical measurements reveals that freshwater inputs and biological drawdown decrease surface ocean inorganic carbon levels more than they are increased by WDW entrainment, resulting in an estimated annual carbon sink of 0.033 ± 0.021 Pg C yr-1. Although relatively less efficient for carbon uptake than the global oceans, the summertime Weddell Gyre suppresses the winter outgassing signal, while its biological pump and deep water formation act as key conduits for transporting natural and anthropogenic carbon to the deep ocean where they can reside for long timescales.
Southern Ocean, Weddell Gyre, ocean carbon cycle, neural network, air-sea exchange of CO2, observations
0886-6236
288-306
Brown, Peter J.
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Jullion, Loïc
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Landschützer, Peter
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Bakker, Dorothee C.E.
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Naveira Garabato, Alberto C.
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Meredith, Michael P.
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Torres-Valdés, Sinhué
c2fe3f1d-84b4-4f87-9fa0-30db16660ad4
Watson, Andrew
b68dca57-fe43-4257-9083-9c450b5d0575
Hoppema, Mario
6f021392-ab2f-4167-8cb0-016b601d392e
Loose, Brice
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Jones, Elizabeth M.
cb5969b2-d139-4c67-acae-5e9405adf3a6
Telszewski, Maciej
3881bce6-c134-409d-87c6-459d08af9824
Jones, Steve D.
b3205c85-5c0e-46bf-be77-8d66fd4961aa
Wanninkhof, Rik
1cb5c6a7-1506-4645-ac88-58c53a0ca22a
Brown, Peter J.
29f4e81e-e0c4-4147-984b-0215571fb2ca
Jullion, Loïc
e72025ed-bc3d-4c9f-a78e-4b41cb1c6da9
Landschützer, Peter
0013ecb7-ae48-427c-86bb-0bb9a7762834
Bakker, Dorothee C.E.
c89339eb-bee7-49f7-9410-dc317a009042
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Meredith, Michael P.
25fd5f1c-f3ed-40a2-af59-5a7074a25fcd
Torres-Valdés, Sinhué
c2fe3f1d-84b4-4f87-9fa0-30db16660ad4
Watson, Andrew
b68dca57-fe43-4257-9083-9c450b5d0575
Hoppema, Mario
6f021392-ab2f-4167-8cb0-016b601d392e
Loose, Brice
64fb1ea7-f908-4fe2-a0c1-156c9c2c18e7
Jones, Elizabeth M.
cb5969b2-d139-4c67-acae-5e9405adf3a6
Telszewski, Maciej
3881bce6-c134-409d-87c6-459d08af9824
Jones, Steve D.
b3205c85-5c0e-46bf-be77-8d66fd4961aa
Wanninkhof, Rik
1cb5c6a7-1506-4645-ac88-58c53a0ca22a

Brown, Peter J., Jullion, Loïc, Landschützer, Peter, Bakker, Dorothee C.E., Naveira Garabato, Alberto C., Meredith, Michael P., Torres-Valdés, Sinhué, Watson, Andrew, Hoppema, Mario, Loose, Brice, Jones, Elizabeth M., Telszewski, Maciej, Jones, Steve D. and Wanninkhof, Rik (2015) Carbon dynamics of the Weddell Gyre, Southern Ocean. Global Biogeochemical Cycles, 29 (3), 288-306. (doi:10.1002/2014GB005006).

Record type: Article

Abstract

The accumulation of carbon within the Weddell Gyre, and its exchanges across the gyre boundaries are investigated with three recent full-depth oceanographic sections enclosing this climatically-important region. The combination of carbon measurements with ocean circulation transport estimates from a box inverse analysis reveal that deep water transports associated with Warm Deep Water (WDW) and Weddell Sea Deep Water dominate the gyre's carbon budget, while a dual-cell vertical overturning circulation leads to both upwelling and the delivery of large quantities of carbon to the deep ocean. Historical sea surface pCO2 observations, interpolated using a neural network technique, confirm the net summertime sink of 0.044 to 0.058 ± 0.010 Pg C yr-1 derived from the inversion. However, a wintertime outgassing signal similar in size results in a statistically insignificant annual air-to-sea CO2 flux of 0.002 ± 0.007 Pg C yr-1 (mean 1998-2011) to 0.012 ± 0.024 Pg C yr-1 (mean 2008-2010) to be diagnosed for the Weddell Gyre. A surface layer carbon balance, independently derived from in situ biogeochemical measurements reveals that freshwater inputs and biological drawdown decrease surface ocean inorganic carbon levels more than they are increased by WDW entrainment, resulting in an estimated annual carbon sink of 0.033 ± 0.021 Pg C yr-1. Although relatively less efficient for carbon uptake than the global oceans, the summertime Weddell Gyre suppresses the winter outgassing signal, while its biological pump and deep water formation act as key conduits for transporting natural and anthropogenic carbon to the deep ocean where they can reside for long timescales.

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Accepted/In Press date: February 2015
Published date: March 2015
Keywords: Southern Ocean, Weddell Gyre, ocean carbon cycle, neural network, air-sea exchange of CO2, observations
Organisations: Marine Biogeochemistry, Physical Oceanography, National Oceanography Centre, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 374633
URI: http://eprints.soton.ac.uk/id/eprint/374633
ISSN: 0886-6236
PURE UUID: 6785edf4-56a2-49aa-b4bd-1da42946727b

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Date deposited: 24 Feb 2015 10:16
Last modified: 07 Oct 2019 18:29

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Contributors

Author: Peter J. Brown
Author: Loïc Jullion
Author: Peter Landschützer
Author: Dorothee C.E. Bakker
Author: Michael P. Meredith
Author: Sinhué Torres-Valdés
Author: Andrew Watson
Author: Mario Hoppema
Author: Brice Loose
Author: Elizabeth M. Jones
Author: Maciej Telszewski
Author: Steve D. Jones
Author: Rik Wanninkhof

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