BGD Biogeosciences Discussions BGD Biogeosciences Discuss. 1810-6285 Göttingen, Germany 10.5194/bgd-8-10797-2011 A model study on the sensitivity of surface ocean CO<sub>2</sub> pressure with respect to the CO<sub>2</sub> gas exchange rate Landschützer P. 1 5 Tjiputra J. F. 1 2 Assmann K. 4 Heinze C. 1 2 3 Geophysical Institute, University of Bergen, Bergen, Norway Bjerknes Centre for Climate Research, Bergen, Norway Uni Bjerknes Centre, Uni Research, Bergen, Norway British Antarctic Survey, High Cross, Madingley Road, Cambridge, UK now at: School of Environmental Sciences, University of East Anglia, Norwich, UK European Commission GREENCYCLESII - Anticipating climate change and biospheric feedbacks within the Earth system to 2200 (238366) COMBINE - Comprehensive Modelling of the Earth system for better climate prediction and projection (226520) COCOS - Coordination Action Carbon Observation System (212196) 08 11 2011 8 6 10797 10821 Copyright: © 2011 P. Landschützer et al. 2011 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/8/10797/2011/bgd-8-10797-2011.html The full text article is available as a PDF file from https://bg.copernicus.org/preprints/8/10797/2011/bgd-8-10797-2011.pdf

Rising CO<sub>2</sub> concentrations in the atmosphere and a changing climate are expected to alter the air-sea CO<sub>2</sub> flux through changes in the respective control factors for gas exchange. In this study we determine the sensitivity of the CO<sub>2</sub> fluxes on the gas transfer velocity using the MICOM-HAMOCC isopycnic carbon cycle model. The monthly generated MICOM-HAMOCC output data are suitable to investigate seasonal variabilities concerning the exchange of CO<sub>2</sub>. In a series of 3 sensitivity runs the wind dependent gas exchange rate is increased by 44%, both in the northern and southern westerly regions, as well as in the equatorial area to investigate the effect of regional variations of the gas transfer rate on the air-sea fluxes and the distribution of the ocean surface <i>p</i>CO<sub>2</sub>. For the period between 1948–2009, the results show that locally increasing gas transfer rates do not play an important role concerning the global uptake of carbon from the atmosphere. While effects on a global and annual scale are low, the regional and intra-annual variability shows remarkable variations in the gas fluxes and the surface <i>p</i>CO<sub>2</sub>. An accurate quantification of the variable gas transfer velocity therefore provides a potential source to enhance model predictions over small spatial and temporal scales and to successfully reconcile model results on surface <i>p</i>CO<sub>2</sub> and air-sea CO<sub>2</sub> fluxes with observations.

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