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On the influence of marine biogeochemical processes over CO2 exchange between the atmosphere and ocean

On the influence of marine biogeochemical processes over CO2 exchange between the atmosphere and ocean
On the influence of marine biogeochemical processes over CO2 exchange between the atmosphere and ocean

The ocean holds a large reservoir of carbon dioxide (CO2), and mitigates climate change through uptake of anthropogenic CO2. Fluxes of CO2 between the atmosphere and surface ocean are regulated by a number of physical and biogeochemical processes, resulting in a spatiotemporally heterogeneous CO2 distribution. Determining the influence of each individual process is useful for interpreting marine carbonate system observations, and is also necessary to investigate how changes in these drivers could affect air-sea CO2 exchange. Biogeochemical processes exert an influence primarily through modifying seawater dissolved inorganic carbon (C T) and total alkalinity (A T), thus changing the seawater partial pressure of CO2 (p sw). Here, we propose a novel conceptual framework through which the size of the CO2 source or sink generated by any biogeochemical process, denoted Φ, can be evaluated. This is based on the 'isocapnic quotient' (Q), which defines the trajectory through (A T,C T) phase space for which there is no change in p sw. We discuss the limitations and uncertainties inherent in this technique, which are negligible for most practical purposes, and its links with existing, related approaches. We investigate the effect on Φ of spatiotemporal heterogeneity in Q in the present day surface ocean for several key biogeochemical processes. This leads the magnitude of the CO2 source or sink generated by processes that modify A T to vary spatiotemporally. Finally, we consider how the strength of each process as a CO2 source or sink may change in a warmer, higher-CO2 future ocean.

Air-sea gas exchange, Calcification, Carbon dioxide, Marine carbonate system
0304-4203
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Daniels, Chris J.
aec2572b-e302-4f8e-ab7a-86b8bdf1c155
Wolf-Gladrow, Dieter A.
87c29592-0b4d-415c-bedc-6be7d62fecd9
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Daniels, Chris J.
aec2572b-e302-4f8e-ab7a-86b8bdf1c155
Wolf-Gladrow, Dieter A.
87c29592-0b4d-415c-bedc-6be7d62fecd9
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Humphreys, Matthew P., Daniels, Chris J., Wolf-Gladrow, Dieter A., Tyrrell, Toby and Achterberg, Eric P. (2017) On the influence of marine biogeochemical processes over CO2 exchange between the atmosphere and ocean. Marine Chemistry. (doi:10.1016/j.marchem.2017.12.006).

Record type: Article

Abstract

The ocean holds a large reservoir of carbon dioxide (CO2), and mitigates climate change through uptake of anthropogenic CO2. Fluxes of CO2 between the atmosphere and surface ocean are regulated by a number of physical and biogeochemical processes, resulting in a spatiotemporally heterogeneous CO2 distribution. Determining the influence of each individual process is useful for interpreting marine carbonate system observations, and is also necessary to investigate how changes in these drivers could affect air-sea CO2 exchange. Biogeochemical processes exert an influence primarily through modifying seawater dissolved inorganic carbon (C T) and total alkalinity (A T), thus changing the seawater partial pressure of CO2 (p sw). Here, we propose a novel conceptual framework through which the size of the CO2 source or sink generated by any biogeochemical process, denoted Φ, can be evaluated. This is based on the 'isocapnic quotient' (Q), which defines the trajectory through (A T,C T) phase space for which there is no change in p sw. We discuss the limitations and uncertainties inherent in this technique, which are negligible for most practical purposes, and its links with existing, related approaches. We investigate the effect on Φ of spatiotemporal heterogeneity in Q in the present day surface ocean for several key biogeochemical processes. This leads the magnitude of the CO2 source or sink generated by processes that modify A T to vary spatiotemporally. Finally, we consider how the strength of each process as a CO2 source or sink may change in a warmer, higher-CO2 future ocean.

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More information

Accepted/In Press date: 19 December 2017
e-pub ahead of print date: 27 December 2017
Keywords: Air-sea gas exchange, Calcification, Carbon dioxide, Marine carbonate system

Identifiers

Local EPrints ID: 417567
URI: https://eprints.soton.ac.uk/id/eprint/417567
ISSN: 0304-4203
PURE UUID: fcdea18d-5a95-4797-80b0-39d0f6049748
ORCID for Toby Tyrrell: ORCID iD orcid.org/0000-0002-1002-1716

Catalogue record

Date deposited: 05 Feb 2018 17:30
Last modified: 10 Dec 2019 01:54

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