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Multidecadal accumulation of anthropogenic and remineralized dissolved inorganic carbon along the Extended Ellett Line in the northeast Atlantic Ocean

Multidecadal accumulation of anthropogenic and remineralized dissolved inorganic carbon along the Extended Ellett Line in the northeast Atlantic Ocean
Multidecadal accumulation of anthropogenic and remineralized dissolved inorganic carbon along the Extended Ellett Line in the northeast Atlantic Ocean
Marine carbonate chemistry measurements have been carried out annually since 2009 during UK research cruises along the Extended Ellett Line (EEL), a hydrographic transect in the northeast Atlantic Ocean. The EEL intersects several water masses that are key to the global thermohaline circulation, and therefore the cruises sample a region in which it is critical to monitor secular physical and biogeochemical changes. We have combined results from these EEL cruises with existing quality-controlled observational data syntheses to produce a hydrographic time-series for the EEL from 1981 to 2013. This reveals multi-decadal increases in dissolved inorganic carbon (DIC) throughout the water column, with a near-surface maximum rate of 1.80 ± 0.45 µmol kg-1 yr-1. Anthropogenic CO2 accumulation was assessed, using simultaneous changes in apparent oxygen utilization (AOU) and total alkalinity (TA) as proxies for the biogeochemical processes that influence DIC. The stable carbon isotope composition of DIC (?13CDIC) was also determined, and used as an independent test of our method. We calculated a volume-integrated anthropogenic CO2 accumulation rate of 2.8 ± 0.4 mg-C m-3 yr-1 along the EEL, which is about double the global mean. The anthropogenic CO2 component accounts for only 31 ± 6 % of the total DIC increase. The remainder is derived from increased organic matter remineralization, which we attribute to the lateral redistribution of water masses that accompanies subpolar gyre contraction. Output from a general circulation-ecosystem model demonstrates that spatiotemporal heterogeneity in the observations has not significantly biased our multi-decadal rate-of-change calculations, and indicates that the EEL observations have been tracking distal changes in the surrounding North Atlantic and Nordic Seas.
Anthropogenic carbon dioxide, Dissolved inorganic carbon, Time series, Extended Ellett Line, Suess effect, North Atlantic subpolar gyre
0886-6236
293-310
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Griffiths, Alex M.
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Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Holliday, N. Penny
358b0b33-f30b-44fd-a193-88365bbf2c79
Rérolle, Victoire M.C.
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Menzel Barraqueta, Jan-Lukas
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Couldrey, Matthew P.
8b4a79ca-0ba6-4c2f-b4e0-8934242497b5
Oliver, Kevin I.C.
588b11c6-4d0c-4c59-94e2-255688474987
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Esposito, Mario
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Boyce, Adrian J.
e21e60d3-a9ab-4cad-9bd8-f6680f3dbd7f
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Griffiths, Alex M.
d578f89f-bba1-4a09-a6aa-f32af3ce8f94
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Holliday, N. Penny
358b0b33-f30b-44fd-a193-88365bbf2c79
Rérolle, Victoire M.C.
454aa1fc-b776-4df7-a763-721155a7be40
Menzel Barraqueta, Jan-Lukas
d7cca559-7992-4f9e-8255-e5bd6a7d0091
Couldrey, Matthew P.
8b4a79ca-0ba6-4c2f-b4e0-8934242497b5
Oliver, Kevin I.C.
588b11c6-4d0c-4c59-94e2-255688474987
Hartman, Susan E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Esposito, Mario
921bdd4b-11cd-4d53-9b3c-31830987281e
Boyce, Adrian J.
e21e60d3-a9ab-4cad-9bd8-f6680f3dbd7f

Humphreys, Matthew P., Griffiths, Alex M., Achterberg, Eric P., Holliday, N. Penny, Rérolle, Victoire M.C., Menzel Barraqueta, Jan-Lukas, Couldrey, Matthew P., Oliver, Kevin I.C., Hartman, Susan E., Esposito, Mario and Boyce, Adrian J. (2016) Multidecadal accumulation of anthropogenic and remineralized dissolved inorganic carbon along the Extended Ellett Line in the northeast Atlantic Ocean. Global Biogeochemical Cycles, 30 (2), 293-310. (doi:10.1002/2015GB005246).

Record type: Article

Abstract

Marine carbonate chemistry measurements have been carried out annually since 2009 during UK research cruises along the Extended Ellett Line (EEL), a hydrographic transect in the northeast Atlantic Ocean. The EEL intersects several water masses that are key to the global thermohaline circulation, and therefore the cruises sample a region in which it is critical to monitor secular physical and biogeochemical changes. We have combined results from these EEL cruises with existing quality-controlled observational data syntheses to produce a hydrographic time-series for the EEL from 1981 to 2013. This reveals multi-decadal increases in dissolved inorganic carbon (DIC) throughout the water column, with a near-surface maximum rate of 1.80 ± 0.45 µmol kg-1 yr-1. Anthropogenic CO2 accumulation was assessed, using simultaneous changes in apparent oxygen utilization (AOU) and total alkalinity (TA) as proxies for the biogeochemical processes that influence DIC. The stable carbon isotope composition of DIC (?13CDIC) was also determined, and used as an independent test of our method. We calculated a volume-integrated anthropogenic CO2 accumulation rate of 2.8 ± 0.4 mg-C m-3 yr-1 along the EEL, which is about double the global mean. The anthropogenic CO2 component accounts for only 31 ± 6 % of the total DIC increase. The remainder is derived from increased organic matter remineralization, which we attribute to the lateral redistribution of water masses that accompanies subpolar gyre contraction. Output from a general circulation-ecosystem model demonstrates that spatiotemporal heterogeneity in the observations has not significantly biased our multi-decadal rate-of-change calculations, and indicates that the EEL observations have been tracking distal changes in the surrounding North Atlantic and Nordic Seas.

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Accepted/In Press date: 26 January 2016
e-pub ahead of print date: 20 February 2016
Published date: February 2016
Keywords: Anthropogenic carbon dioxide, Dissolved inorganic carbon, Time series, Extended Ellett Line, Suess effect, North Atlantic subpolar gyre
Organisations: Ocean and Earth Science, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 387162
URI: http://eprints.soton.ac.uk/id/eprint/387162
ISSN: 0886-6236
PURE UUID: 97f3521d-2625-474f-b01d-a2a3f21fff3c
ORCID for Matthew P. Humphreys: ORCID iD orcid.org/0000-0002-9371-7128

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Date deposited: 10 Feb 2016 09:44
Last modified: 28 Apr 2022 02:11

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Contributors

Author: Matthew P. Humphreys ORCID iD
Author: Alex M. Griffiths
Author: N. Penny Holliday
Author: Victoire M.C. Rérolle
Author: Jan-Lukas Menzel Barraqueta
Author: Matthew P. Couldrey
Author: Susan E. Hartman
Author: Mario Esposito
Author: Adrian J. Boyce

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