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Key controls on the seasonal and interannual variations of the carbonate system and air-sea CO2 flux in the Northeast Atlantic (Bay of Biscay)

Key controls on the seasonal and interannual variations of the carbonate system and air-sea CO2 flux in the Northeast Atlantic (Bay of Biscay)
Key controls on the seasonal and interannual variations of the carbonate system and air-sea CO2 flux in the Northeast Atlantic (Bay of Biscay)
Biogeochemical variations of surface water in the Northeast Atlantic (Bay of Biscay) were examined using high-frequency underway measurements combined with monthly sampling of carbon-related variables. The mechanisms controlling seasonal CO2 variability were investigated by distinguishing the contributions of biological and physical processes to the monthly changes in dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2). The seasonality of DIC (47–81?µmol?kg?1) had a single peak with a winter maximum primarily driven by vertical mixing and a summer minimum driven by spring biological removal. Non-Redfield C:N uptake was observed in the nutrient-depleted summer but not during the spring bloom. In the North Atlantic, pCO2 seasonality shows a latitudinal transition: from the temperature-dominated oligotrophic subtropical gyre to the subpolar region where pCO2 is dominated by changing concentrations of DIC. In the midlatitude Bay of Biscay, the annual cycle of pCO2 (61–75 µatm) showed a double-peak distribution. The summer pCO2 peak was mainly driven by temperature increase, while the winter peak resulted from the dominant effect of entrainment of subsurface water. Interannual variations of DIC were more pronounced in winter and were driven by the changes in the strength of winter mixing. Higher wintertime concentrations and seasonal amplitudes of DIC were observed in cold years when the mixed-layer depths were deeper, which appears to be associated with negative phases of the North Atlantic Oscillation. The Bay of Biscay shows a decrease of CO2 uptake in 2008–2010 (?0.97 and ?0.75?mol?m?2?yr?1) compared to 2002–2004 (?1.47 and ?1.68?mol?m?2?yr?1).
seasonal, interannual, carbonate system, CO2 flux, North Atlantic, Bay of Biscay
0148-0227
785-800
Jiang, Zong-Pei
801435b8-c2e5-476e-84c0-b49ef65ad382
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hartman, Sue
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Hartman, Mark C.
cdd63b60-f89a-4ef8-842d-7803f8213c18
Dumousseaud, Cynthia
31cc4879-0d45-4674-8eba-93105ee25c2e
Padin, Xose Antonio
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Skjelvan, Ingunn
9190d289-c31c-413b-9d87-5173201bbb55
González-Pola, César
36ca5cc3-ebb8-40e7-8079-2cf2912b7773
Jiang, Zong-Pei
801435b8-c2e5-476e-84c0-b49ef65ad382
Hydes, David J.
ac7371d4-c2b9-4926-bb77-ce58480ecff7
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Hartman, Sue
2f74a439-395a-4ee7-89a2-eff4cc8d9481
Hartman, Mark C.
cdd63b60-f89a-4ef8-842d-7803f8213c18
Dumousseaud, Cynthia
31cc4879-0d45-4674-8eba-93105ee25c2e
Padin, Xose Antonio
9f90fe20-cfd9-49e1-89ae-6a13e36204ee
Skjelvan, Ingunn
9190d289-c31c-413b-9d87-5173201bbb55
González-Pola, César
36ca5cc3-ebb8-40e7-8079-2cf2912b7773

Jiang, Zong-Pei, Hydes, David J., Tyrrell, Toby, Hartman, Sue, Hartman, Mark C., Dumousseaud, Cynthia, Padin, Xose Antonio, Skjelvan, Ingunn and González-Pola, César (2013) Key controls on the seasonal and interannual variations of the carbonate system and air-sea CO2 flux in the Northeast Atlantic (Bay of Biscay). Journal of Geophysical Research, 118 (2), 785-800. (doi:10.1002/jgrc.20087).

Record type: Article

Abstract

Biogeochemical variations of surface water in the Northeast Atlantic (Bay of Biscay) were examined using high-frequency underway measurements combined with monthly sampling of carbon-related variables. The mechanisms controlling seasonal CO2 variability were investigated by distinguishing the contributions of biological and physical processes to the monthly changes in dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2). The seasonality of DIC (47–81?µmol?kg?1) had a single peak with a winter maximum primarily driven by vertical mixing and a summer minimum driven by spring biological removal. Non-Redfield C:N uptake was observed in the nutrient-depleted summer but not during the spring bloom. In the North Atlantic, pCO2 seasonality shows a latitudinal transition: from the temperature-dominated oligotrophic subtropical gyre to the subpolar region where pCO2 is dominated by changing concentrations of DIC. In the midlatitude Bay of Biscay, the annual cycle of pCO2 (61–75 µatm) showed a double-peak distribution. The summer pCO2 peak was mainly driven by temperature increase, while the winter peak resulted from the dominant effect of entrainment of subsurface water. Interannual variations of DIC were more pronounced in winter and were driven by the changes in the strength of winter mixing. Higher wintertime concentrations and seasonal amplitudes of DIC were observed in cold years when the mixed-layer depths were deeper, which appears to be associated with negative phases of the North Atlantic Oscillation. The Bay of Biscay shows a decrease of CO2 uptake in 2008–2010 (?0.97 and ?0.75?mol?m?2?yr?1) compared to 2002–2004 (?1.47 and ?1.68?mol?m?2?yr?1).

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Published date: February 2013
Keywords: seasonal, interannual, carbonate system, CO2 flux, North Atlantic, Bay of Biscay
Organisations: Marine Biogeochemistry, Ocean Biochemistry & Ecosystems

Identifiers

Local EPrints ID: 350714
URI: http://eprints.soton.ac.uk/id/eprint/350714
ISSN: 0148-0227
PURE UUID: e97a3d51-eab0-4c3a-bf27-3ca2cecdf696
ORCID for Toby Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716
ORCID for Cynthia Dumousseaud: ORCID iD orcid.org/0000-0001-5995-902X

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Date deposited: 28 Mar 2013 15:37
Last modified: 25 Jun 2024 01:42

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Contributors

Author: Zong-Pei Jiang
Author: David J. Hydes
Author: Toby Tyrrell ORCID iD
Author: Sue Hartman
Author: Mark C. Hartman
Author: Xose Antonio Padin
Author: Ingunn Skjelvan
Author: César González-Pola

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