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Carbon exchange between a shelf sea and the ocean: The Hebrides Shelf, west of Scotland

Carbon exchange between a shelf sea and the ocean: The Hebrides Shelf, west of Scotland
Carbon exchange between a shelf sea and the ocean: The Hebrides Shelf, west of Scotland
Global mass balance calculations indicate the majority of particulate organic carbon (POC) exported from shelf seas is transferred via downslope exchange processes. Here we demonstrate the downslope flux of POC from the Hebrides Shelf is approximately 3-to-5-fold larger per unit length/area than the global mean. To reach this conclusion we quantified the offshore transport of particulate and dissolved carbon fractions via the “Ekman Drain”, a strong downwelling feature of the NW European Shelf circulation, and subsequently compared these fluxes to simultaneous regional air-sea CO2 fluxes and on-shore wind-driven Ekman fluxes to constrain the carbon dynamics of this shelf. Along the shelf break we estimate a mean offshelf total carbon (dissolved?+?particulate) flux of 4.2 tonnes C m?1 d?1 compared to an onshelf flux of 4.5 tonnes C m?1 d?1. Organic carbon represented 3.3% of the onshelf carbon flux but 6.4% of the offshelf flux indicating net organic carbon export. Dissolved organic carbon represented 95% and POC 5% of the exported organic carbon pool. When scaled along the shelf break the total offshelf POC flux (0.007 Tg C d?1) was found to be three times larger than the regional air-sea CO2 ingassing flux (0.0021 Tg C d?1), an order of magnitude larger than the particulate inorganic carbon flux (0.0003 Tg C d?1) but far smaller than the DIC (2.03 Tg C d?1) or DOC (0.13 Tg C d?1) fluxes. Significant spatial heterogeneity in the Ekman drain transport confirms that offshelf carbon fluxes via this mechanism are also spatially heterogeneous. This article is protected by copyright. All rights reserved.
Shelf exchange, Carbon flux, Ekman drain
4522-4544
Painter, Stuart
29e32f35-4ee8-4654-b305-4dbe5a312295
Hartman, S.E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Kivimae, Caroline
f855a4f5-00a6-4fee-bf39-fd72472b9959
Salt, Lesley
5cbd1aa1-0f21-42b1-8ed3-f3367c248dcd
Clargo, Nicola
a6942ea6-f00b-443c-a5b8-da9a20c4792e
Bozec, Yann
8845b447-a496-4608-a635-b25af5cc4d66
Daniels, Chris J.
e4a51f9d-efe6-413a-8d3f-3f1eda5ce79f
Jones, Sam
15984b74-dcf2-4218-821a-98a771b64648
Hemsley, Victoria S.
a4c30626-eaea-4817-bea2-d48f757b52fe
Munns, Lucie
859a0d0d-fccc-458d-b218-b1462282d0cd
Allen, Stephanie R.
5078fbb4-6c8e-4a29-8d35-b332f8ae59b7
Painter, Stuart
29e32f35-4ee8-4654-b305-4dbe5a312295
Hartman, S.E.
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Kivimae, Caroline
f855a4f5-00a6-4fee-bf39-fd72472b9959
Salt, Lesley
5cbd1aa1-0f21-42b1-8ed3-f3367c248dcd
Clargo, Nicola
a6942ea6-f00b-443c-a5b8-da9a20c4792e
Bozec, Yann
8845b447-a496-4608-a635-b25af5cc4d66
Daniels, Chris J.
e4a51f9d-efe6-413a-8d3f-3f1eda5ce79f
Jones, Sam
15984b74-dcf2-4218-821a-98a771b64648
Hemsley, Victoria S.
a4c30626-eaea-4817-bea2-d48f757b52fe
Munns, Lucie
859a0d0d-fccc-458d-b218-b1462282d0cd
Allen, Stephanie R.
5078fbb4-6c8e-4a29-8d35-b332f8ae59b7

Painter, Stuart, Hartman, S.E., Kivimae, Caroline, Salt, Lesley, Clargo, Nicola, Bozec, Yann, Daniels, Chris J., Jones, Sam, Hemsley, Victoria S., Munns, Lucie and Allen, Stephanie R. (2016) Carbon exchange between a shelf sea and the ocean: The Hebrides Shelf, west of Scotland. Journal of Geophysical Research: Oceans, 121 (7), 4522-4544. (doi:10.1002/2015JC011599).

Record type: Article

Abstract

Global mass balance calculations indicate the majority of particulate organic carbon (POC) exported from shelf seas is transferred via downslope exchange processes. Here we demonstrate the downslope flux of POC from the Hebrides Shelf is approximately 3-to-5-fold larger per unit length/area than the global mean. To reach this conclusion we quantified the offshore transport of particulate and dissolved carbon fractions via the “Ekman Drain”, a strong downwelling feature of the NW European Shelf circulation, and subsequently compared these fluxes to simultaneous regional air-sea CO2 fluxes and on-shore wind-driven Ekman fluxes to constrain the carbon dynamics of this shelf. Along the shelf break we estimate a mean offshelf total carbon (dissolved?+?particulate) flux of 4.2 tonnes C m?1 d?1 compared to an onshelf flux of 4.5 tonnes C m?1 d?1. Organic carbon represented 3.3% of the onshelf carbon flux but 6.4% of the offshelf flux indicating net organic carbon export. Dissolved organic carbon represented 95% and POC 5% of the exported organic carbon pool. When scaled along the shelf break the total offshelf POC flux (0.007 Tg C d?1) was found to be three times larger than the regional air-sea CO2 ingassing flux (0.0021 Tg C d?1), an order of magnitude larger than the particulate inorganic carbon flux (0.0003 Tg C d?1) but far smaller than the DIC (2.03 Tg C d?1) or DOC (0.13 Tg C d?1) fluxes. Significant spatial heterogeneity in the Ekman drain transport confirms that offshelf carbon fluxes via this mechanism are also spatially heterogeneous. This article is protected by copyright. All rights reserved.

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Submitted date: 22 December 2015
Accepted/In Press date: 21 May 2016
e-pub ahead of print date: 2 July 2016
Keywords: Shelf exchange, Carbon flux, Ekman drain
Organisations: Ocean and Earth Science, Marine Biogeochemistry, Ocean Biochemistry & Ecosystems, National Oceanography Centre

Identifiers

Local EPrints ID: 391944
URI: http://eprints.soton.ac.uk/id/eprint/391944
PURE UUID: edfd789d-0060-40ba-97d2-fe8154326f12
ORCID for Stephanie R. Allen: ORCID iD orcid.org/0000-0001-5414-1931

Catalogue record

Date deposited: 26 May 2016 14:20
Last modified: 09 Jan 2022 06:06

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Contributors

Author: Stuart Painter
Author: S.E. Hartman
Author: Caroline Kivimae
Author: Lesley Salt
Author: Nicola Clargo
Author: Yann Bozec
Author: Chris J. Daniels
Author: Sam Jones
Author: Victoria S. Hemsley
Author: Lucie Munns
Author: Stephanie R. Allen ORCID iD

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