The University of Southampton
University of Southampton Institutional Repository

On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?
On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?
The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ?pCO2, and the temperature and salinity-dependent solubility coefficient, ?. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ?pCO2 and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ?pCO2 and ? on a range of timescales. On interannual and shorter timescales, both ?pCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ?pCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability.
Carbon Flux, Gas Transfer Velocity, Carbon Cycle, Ocean Model, Climate Dynamics, Variability
0886-6236
787-802
Couldrey, Matthew
d31f984e-e696-4d7d-babb-6a17925b0391
Oliver, Kevin
588b11c6-4d0c-4c59-94e2-255688474987
Yool, Andrew
882aeb0d-dda0-405e-844c-65b68cce5017
Halloran, Paul
4d3c2439-a9c5-415d-af0a-92529a850610
Achterberg, Eric
685ce961-8c45-4503-9f03-50f6561202b9
Couldrey, Matthew
d31f984e-e696-4d7d-babb-6a17925b0391
Oliver, Kevin
588b11c6-4d0c-4c59-94e2-255688474987
Yool, Andrew
882aeb0d-dda0-405e-844c-65b68cce5017
Halloran, Paul
4d3c2439-a9c5-415d-af0a-92529a850610
Achterberg, Eric
685ce961-8c45-4503-9f03-50f6561202b9

Couldrey, Matthew, Oliver, Kevin, Yool, Andrew, Halloran, Paul and Achterberg, Eric (2016) On which timescales do gas transfer velocities control North Atlantic CO2 flux variability? Global Biogeochemical Cycles, 30 (5), 787-802. (doi:10.1002/2015GB005267).

Record type: Article

Abstract

The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ?pCO2, and the temperature and salinity-dependent solubility coefficient, ?. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ?pCO2 and k both contribute significantly to interannual F variability, but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here, we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ?pCO2 and ? on a range of timescales. On interannual and shorter timescales, both ?pCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ?pCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of non-seasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer term flux variability.

Text
dPCO2_Draft4.pdf - Accepted Manuscript
Download (1MB)

More information

Accepted/In Press date: 12 April 2016
e-pub ahead of print date: 31 May 2016
Published date: 11 June 2016
Keywords: Carbon Flux, Gas Transfer Velocity, Carbon Cycle, Ocean Model, Climate Dynamics, Variability
Organisations: Marine Systems Modelling, Physical Oceanography

Identifiers

Local EPrints ID: 392047
URI: http://eprints.soton.ac.uk/id/eprint/392047
ISSN: 0886-6236
PURE UUID: cb0fe876-4cde-4f2e-86ed-38aace1edc9a

Catalogue record

Date deposited: 14 Apr 2016 13:25
Last modified: 14 Mar 2024 23:34

Export record

Altmetrics

Contributors

Author: Matthew Couldrey
Author: Kevin Oliver
Author: Andrew Yool
Author: Paul Halloran
Author: Eric Achterberg

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×