FN Archimer Export Format PT J TI Key Uncertainties in the Recent Air‐Sea Flux of CO2 BT AF Woolf, D.K. Shutler, J.D. Goddijn‐Murphy, L. Watson, A.J. Chapron, Bertrand Nightingale, P.D. Donlon, C.J. Piskozub, J. Yelland, M.J. Ashton, Ian Holding, T. Schuster, U. GIRARD-ARDHUIN, Fanny Grouazel, Antoine Piolle, Jean-Francois Warren, M. Wrobel‐Niedzwiecka, I. Land, P.E. Torres, R. Prytherch, J. Moat, B. Hanafin, J. ARDHUIN, Fabrice Paul, Frederic AS 1:1;2:2;3:3;4:2;5:4;6:5;7:6;8:7;9:8;10:9;11:2;12:2;13:4;14:4;15:4;16:5;17:7;18:5;19:5;20:8;21:8;22:10;23:10;24:4; FF 1:;2:;3:;4:;5:PDG-ODE-LOPS-SIAM;6:;7:;8:;9:;10:;11:;12:;13:PDG-ODE-LOPS-SIAM;14:PDG-ODE-LOPS-SIAM;15:PDG-ODE-LOPS-SIAM;16:;17:;18:;19:;20:;21:;22:;23:;24:PDG-ODE-LOPS-SIAM; C1 International Centre for Island Technology, Heriot‐Watt University, UK College of Life and Environmental Sciences, University of Exeter, UK University of the Highlands and Islands ,UK Ifremer, Univ. Brest, CNRS, IRD, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM Brest, France Plymouth Marine Laboratory, UK European Space Agency ,The Netherlands Institute of Oceanology, Polish Academy of Sciences Sopot ,Poland National Oceanography Centre Southampton ,UK College of Engineering, Mathematics and Physical Sciences, University of Exeter ,UK Ifremer, Univ. Brest, CNRS, IRD, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM Brest, France C2 UNIV HERIOT WATT, UK UNIV EXETER, UK UNIV HIGHLANDS & ISL, UK IFREMER, FRANCE PML, UK ESA, NETHERLANDS POLISH ACAD SCI, POLAND NOC, UK UNIV EXETER, UK CNRS, FRANCE SI BREST SE PDG-ODE-LOPS-SIAM UM LOPS IN WOS Ifremer UMR WOS Cotutelle UMR copubli-france copubli-europe IF 4.608 TC 47 UR https://archimer.ifremer.fr/doc/00513/62450/66754.pdf https://archimer.ifremer.fr/doc/00513/62450/66755.pdf LA English DT Article CR OISO - OCÉAN INDIEN SERVICE D'OBSERVATION DE ;Carbon dioxide;air-sea flux;uncertainty;transfer velocity;sampling AB The contemporary air‐sea flux of CO2 is investigated by the use of an air‐sea flux equation, with particular attention to the uncertainties in global values and their origin with respect to that equation. In particular, uncertainties deriving from the transfer velocity and from sparse upper ocean sampling are investigated. Eight formulations of air‐sea gas transfer velocity are used to evaluate the combined standard uncertainty resulting from several sources of error. Depending on expert opinion, a standard uncertainty in transfer velocity of either ~5% or ~10% can be argued and that will contribute a proportional error in air‐sea flux. The limited sampling of upper ocean fCO2 is readily apparent in the Surface Ocean CO2 Atlas (SOCAT) databases. The effect of sparse sampling on the calculated fluxes was investigated by a bootstrap method; i.e. treating each ship cruise to an oceanic region as a random episode and creating 10 synthetic datasets by randomly selecting episodes with replacement. Convincing values of global net air‐sea flux can only be achieved using upper ocean data collected over several decades, but referenced to a standard year. The global annual referenced values are robust to sparse sampling, but seasonal and regional values exhibit more sampling uncertainty. Additional uncertainties are related to thermal and haline effects and to aspects of air‐sea gas exchange not captured by standard models. An estimate of global net CO2 exchange referenced to 2010 of ‐3.0 ± 0.6 Pg C yr‐1 is proposed, where the uncertainty derives primarily from uncertainty in the transfer velocity. PY 2019 PD DEC SO Global Biogeochemical Cycles SN 0886-6236 PU American Geophysical Union (AGU) VL 33 IS 12 UT 000500764600001 BP 1548 EP 1563 DI 10.1029/2018GB006041 ID 62450 ER EF