Sea-air CO2 fluxes in the Southern Ocean for the period 1990-2009

• Main Authors: Lenton, A, Tilbrook, B, Law, RM, Bakker, D, Doney, SC, Gruber, N, Ishii, M, Hoppema, M, Lovenduski, NS, Matear, RJ, McNeil, BI, Metzl, N, Mikaloff Fletcher, SE, Monteiro, Pedro MS, Rodenbeck, C, Sweeney, C, Takahashi, T
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union (EGU) 2013
• Subjects: Southern Ocean; Sea-air; Regional Carbon Cycle Assessment and Processes; RECCAP; Weather research; Climate research; Austral
• Online Access: http://hdl.handle.net/10204/7466; http://www.biogeosciences.net/10/4037/2013/bg-10-4037-2013.html

Copyright: 2013 European Geosciences Union (EGU). This is an Open Access journal. The journal authorizes the publication of the information herewith contained. Published in European Geosciences Union (EGU), vol. 10, pp 4037–4054 The Southern Ocean (44–75° S) plays a critical role in the global carbon cycle, yet remains one of the most poorly sampled ocean regions. Different approaches have been used to estimate sea–air (sub2) fluxes in this region: synthesis of surface ocean observations, ocean biogeochemical models, and atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Southern Ocean sea–air CO(sub2) fluxes between 1990–2009. Using all models and inversions (26), the integrated median annual sea–air CO(sub2) flux of -0.42 ± 0.07 Pg C yr(sup-1) for the 44–75° S region, is consistent with the -0.27 ± 0.13 Pg C yr(sup-1) calculated using surface observations. The circumpolar region south of 58° S has a small net annual flux (model and inversion median: -0.04 ± 0.07 Pg C yr(sup-1) and observations: +0.04 ± 0.02 Pg C yr(sup-1), with most of the net annual flux located in the 44 to 58° S circumpolar band (model and inversion median: -0.36 ± 0.09 Pg C yr(sup-1) and observations: -0.35 ± 0.09 Pg C yr-1). Seasonally, in the 44–58° S region, the median of 5 ocean biogeochemical models captures the observed sea–air CO(sub2) flux seasonal cycle, while the median of 11 atmospheric inversions shows little seasonal change in the net flux. South of 58° S, neither atmospheric inversions nor ocean biogeochemical models reproduce the phase and amplitude of the observed seasonal sea–air CO(sub2) flux, particularly in the Austral Winter. Importantly, no individual atmospheric inversion or ocean biogeochemical model is capable of reproducing both the observed annual mean uptake and the observed seasonal cycle. This raises concerns about projecting future changes in Southern ...