Natural variability in air–sea gas transfer efficiency of CO2

Yang, M; Smyth, TJ; Kitidis, V; Brown, IJ; Wohl, C; Yelland, MJ; Bell, TG. 2021 Natural variability in air–sea gas transfer efficiency of CO2. Scientific Reports, 11 (1). https://doi.org/10.1038/s41598-021-92947-w

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Official URL: http://dx.doi.org/10.1038/s41598-021-92947-w

Abstract/Summary

The flux of CO2 between the atmosphere and the ocean is often estimated as the air–sea gas concentration difference multiplied by the gas transfer velocity (K660). The first order driver for K660 over the ocean is wind through its influence on near surface hydrodynamics. However, field observations have shown substantial variability in the wind speed dependencies of K660. In this study we measured K660 with the eddy covariance technique during a~ 11,000 km long Southern Ocean transect. In parallel, we made a novel measurement of the gas transfer efficiency (GTE) based on partial equilibration of CO2 using a Segmented Flow Coil Equilibrator system. GTE varied by 20% during the transect, was distinct in different water masses, and related to K660. At a moderate wind speed of 7 m ­s−1, K660 associated with high GTE exceeded K660 with low GTE by 30% in the mean. The sensitivity of K660 towards GTE was stronger at lower wind speeds and weaker at higher wind speeds. Naturally-occurring organics in seawater, some of which are surface active, may be the cause of the variability in GTE and in K660. Neglecting these variations could result in biases in the computed air–sea CO2 fluxes

Item Type: Publication - Article
Additional Information. Not used in RCUK Gateway to Research.: We thank Andrew Meijers (British Antarctic Survey), the chief scientist of the ANDREXII cruise, as well as all the technical, computing, and engineering support on the JCR for accommo�dating and supporting our air–sea fux measurements. We further thank Philip Nightingale (PML) for insightful discussions about the role of surfactants on gas transfer, Daniel Phillips (PML) for assistance in laboratory char�acterization of the SFCEs, and John Prytherch (Stockholm University), Robin Pascal (National Oceanography Centre), and Ian Brooks (University of Leeds) for recommendations concerning the fux system installation on the JCR. Author contributions M.Y. designed the gas transfer efciency measurement system with input from T.B. and C.W. M.Y. and T.B. installed the air–sea fux system on the JCR. M.J.Y. advised on the installation of the fux system on the JCR. M.Y. performed data quality control with input from M.J.Y. and T.B. M.Y. carried out the shipboard measurement with support from C.W. T.S. helped with remote monitoring and quality control of the air–sea fux system. I.B. and V.K. installed and maintained the showerhead pCO2 system. M.Y. wrote the paper with contributions from all authors
Divisions: Plymouth Marine Laboratory > National Capability categories > Long-term Multi-Centre ORCHESTRA
Plymouth Marine Laboratory > Science Areas > Marine Biochemistry and Observations
Depositing User: S Hawkins
Date made live: 16 Jul 2021 12:57
Last Modified: 16 Jul 2021 12:57
URI: http://plymsea.ac.uk/id/eprint/9271

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