BGD Biogeosciences Discussions BGD Biogeosciences Discuss. 1810-6285 Göttingen, Germany 10.5194/bgd-9-16381-2012 Thermal and haline effects on the calculation of air-sea CO<sub>2</sub> fluxes revisited Woolf D. K. 1 Land P. E. 2 Shutler J. D. 2 Goddijn-Murphy L. M. 3 International Centre for Island Technology, Heriot Watt University, Stromness, Orkney KW16 3AW, UK Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1 3DH, UK Environmental Research Institute, University of the Highlands and Islands, Thurso KW14 7JD, UK 16 11 2012 9 11 16381 16417 Copyright: © 2012 D. K. Woolf et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/preprints/9/16381/2012/bgd-9-16381-2012.html The full text article is available as a PDF file from https://bg.copernicus.org/preprints/9/16381/2012/bgd-9-16381-2012.pdf

The presence of vertical temperature and salinity gradients in the upper ocean and the occurrence of variations in temperature and salinity on time scales from hours to many years complicate the calculation of the flux of carbon dioxide (CO<sub>2</sub>) across the sea surface. Temperature and salinity affect the interfacial concentration of aqueous CO<sub>2</sub> primarily through their effect on solubility with lesser effects related to saturated vapour pressure and the relationship between fugacity and partial pressure. The effects of temperature and salinity profiles and changes in the aqueous concentration act primarily through the partitioning of the carbonate system. Contrary to some recent analysis, it is shown that the effect on CO<sub>2</sub> fluxes of a cool skin on the sea surface is large and ubiquitous. An opposing effect on calculated fluxes is related to the occurrence of warm layers near the surface; this effect can be locally large but will usually coincide with periods of low exchange. A salty skin and salinity anomalies in the upper ocean also affect CO<sub>2</sub> flux calculations, though the haline effects are generally weaker than the thermal effects.

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