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Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean

Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean
Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean
The variability in the storage of the oceanic anthropogenic CO2 (Cant) on decadal timescales is evaluated within the main water masses of the Subtropical North Atlantic along 24.5°N. Inorganic carbon measurements on five cruises of the A05 section are used to assess the changes in Cant between 1992 and 2011, using four methods (?C?, TrOCA, ?CT0, TTD). We find good agreement between the Cant distribution and storage obtained using chlorofluorocarbons and CO2 measurements in both the vertical and horizontal scales. Cant distribution shows higher concentrations and greater decadal storage rates in the upper layers with both values decreasing with depth. The greatest enrichment is obserbed in the central water masses, with their upper limb showing a mean annual accumulation of about 1 ?mol kg?1 yr?1 and the lower limb showing, on average, half that value. We detect zonal gradients in the accumulation of Cant. This finding is less clear in the upper waters, where greater variability exists between methods. In accordance with data from time series stations, greater accumulation of Cant is observed in the upper waters of the western basin of the North Atlantic Subtropical Gyre. In intermediate and deep layers, the zonal gradient in the storage of Cant is more robust between methods. The much lower mean storage rates found along the section (<0.25 ?mol kg?1 yr?1) become more obvious when longitudinal differences in the Cant accumulation are considered. In particular, west of 70°W the ventilation by the Labrador Sea Water creates a noticeable accumulation rate up to ?0.5 ?mol kg?1 yr?1 between 1000 and 2500 dbar. If a Transient Stationary State of the Cant distributions is considered, significant bi-decadal trends in the Cant storage rates in the deepest North Atlantic waters are detected, in agreement with recent estimations.
0079-6611
21-32
Guallart, Elisa F.
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Schuster, Ute
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Fajar, Noelia M.
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Legge, Oliver
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Brown, Peter J.
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Pelejero, Carles
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Messias, Marie-Jose
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Calvo, Eva
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Watson, Andrew
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Ríos, Aida F.
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Pérez, Fiz F.
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Guallart, Elisa F.
9bb9b6e2-557e-4bca-8900-348d541be95e
Schuster, Ute
3ba01afd-9a84-46e5-ae83-2e3ae708250f
Fajar, Noelia M.
b3d9fd0a-613e-4598-96bc-42475c8580d1
Legge, Oliver
53710c77-630e-4f85-a30d-12771a40a355
Brown, Peter J.
29f4e81e-e0c4-4147-984b-0215571fb2ca
Pelejero, Carles
519663e3-9509-432d-bd7d-c749497cfdb3
Messias, Marie-Jose
c8227a05-a3e2-4146-975d-0906ae5eacb1
Calvo, Eva
481687a9-d3d5-4868-9fe8-08f4955bcc88
Watson, Andrew
b68dca57-fe43-4257-9083-9c450b5d0575
Ríos, Aida F.
ab17b6af-924c-4ea7-8962-84530a19c4f3
Pérez, Fiz F.
ce4b7b26-a9e5-443c-8200-1d98f132d134

Guallart, Elisa F., Schuster, Ute, Fajar, Noelia M., Legge, Oliver, Brown, Peter J., Pelejero, Carles, Messias, Marie-Jose, Calvo, Eva, Watson, Andrew, Ríos, Aida F. and Pérez, Fiz F. (2015) Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean. Progress in Oceanography, 131, 21-32. (doi:10.1016/j.pocean.2014.11.006).

Record type: Article

Abstract

The variability in the storage of the oceanic anthropogenic CO2 (Cant) on decadal timescales is evaluated within the main water masses of the Subtropical North Atlantic along 24.5°N. Inorganic carbon measurements on five cruises of the A05 section are used to assess the changes in Cant between 1992 and 2011, using four methods (?C?, TrOCA, ?CT0, TTD). We find good agreement between the Cant distribution and storage obtained using chlorofluorocarbons and CO2 measurements in both the vertical and horizontal scales. Cant distribution shows higher concentrations and greater decadal storage rates in the upper layers with both values decreasing with depth. The greatest enrichment is obserbed in the central water masses, with their upper limb showing a mean annual accumulation of about 1 ?mol kg?1 yr?1 and the lower limb showing, on average, half that value. We detect zonal gradients in the accumulation of Cant. This finding is less clear in the upper waters, where greater variability exists between methods. In accordance with data from time series stations, greater accumulation of Cant is observed in the upper waters of the western basin of the North Atlantic Subtropical Gyre. In intermediate and deep layers, the zonal gradient in the storage of Cant is more robust between methods. The much lower mean storage rates found along the section (<0.25 ?mol kg?1 yr?1) become more obvious when longitudinal differences in the Cant accumulation are considered. In particular, west of 70°W the ventilation by the Labrador Sea Water creates a noticeable accumulation rate up to ?0.5 ?mol kg?1 yr?1 between 1000 and 2500 dbar. If a Transient Stationary State of the Cant distributions is considered, significant bi-decadal trends in the Cant storage rates in the deepest North Atlantic waters are detected, in agreement with recent estimations.

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Guallart et al (2015) PiO Accepted Manuscript.pdf - Accepted Manuscript
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Published date: February 2015
Organisations: Marine Physics and Ocean Climate

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Local EPrints ID: 374888
URI: http://eprints.soton.ac.uk/id/eprint/374888
ISSN: 0079-6611
PURE UUID: 259430d7-a535-4ee4-9d10-7946992cab7f

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Date deposited: 04 Mar 2015 16:44
Last modified: 14 Mar 2024 19:16

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Contributors

Author: Elisa F. Guallart
Author: Ute Schuster
Author: Noelia M. Fajar
Author: Oliver Legge
Author: Peter J. Brown
Author: Carles Pelejero
Author: Marie-Jose Messias
Author: Eva Calvo
Author: Andrew Watson
Author: Aida F. Ríos
Author: Fiz F. Pérez

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