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Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas
Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas
Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pH using the total pH scale (pHT), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson's correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 ?atm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises.
1726-4170
4339-4355
Ribas-Ribas, M.
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Rérolle, V.M.C.
cb1aa4ff-d446-40ff-a262-6dccab7dcb50
Bakker, D.C.E.
bd373973-6b47-4d3c-ae49-4f6d894ad660
Kitidis, V.
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Lee, G.A.
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Brown, I.
13b13988-789f-40e2-a2d8-8f326f68eedd
Achterberg, E.P.
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Hardman-Mountford, N.J.
abf4a070-c20c-4978-afcc-b3e8ef7b0e57
Tyrrell, T.
6808411d-c9cf-47a3-88b6-c7c294f2d114
Ribas-Ribas, M.
85a1f816-cfbd-4a9d-83ff-28611827edcd
Rérolle, V.M.C.
cb1aa4ff-d446-40ff-a262-6dccab7dcb50
Bakker, D.C.E.
bd373973-6b47-4d3c-ae49-4f6d894ad660
Kitidis, V.
945c00c4-55ab-4fd2-b912-0b07530ca2e5
Lee, G.A.
ea538fda-20f7-4204-9227-ca90e78dc522
Brown, I.
13b13988-789f-40e2-a2d8-8f326f68eedd
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Hardman-Mountford, N.J.
abf4a070-c20c-4978-afcc-b3e8ef7b0e57
Tyrrell, T.
6808411d-c9cf-47a3-88b6-c7c294f2d114

Ribas-Ribas, M., Rérolle, V.M.C., Bakker, D.C.E., Kitidis, V., Lee, G.A., Brown, I., Achterberg, E.P., Hardman-Mountford, N.J. and Tyrrell, T. (2014) Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas. Biogeosciences, 11 (16), 4339-4355. (doi:10.5194/bg-11-4339-2014).

Record type: Article

Abstract

Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pH using the total pH scale (pHT), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson's correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 ?atm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises.

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Published date: 19 August 2014
Organisations: Ocean and Earth Science

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Local EPrints ID: 368158
URI: http://eprints.soton.ac.uk/id/eprint/368158
ISSN: 1726-4170
PURE UUID: 8968accb-583f-43bf-a206-fb0f265170dd
ORCID for T. Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716

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Date deposited: 19 Aug 2014 10:41
Last modified: 29 Oct 2019 02:04

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