Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 5 2010 10.5194/bg-7-1587-2010 http://www.biogeosciences.net/7/1587/2010/ http://www.biogeosciences.net/7/1587/2010/bg-7-1587-2010.html http://www.biogeosciences.net/7/1587/2010/bg-7-1587-2010.pdf 1587 1606 2010-05-18 Air-Sea CO₂ fluxes in the Atlantic as measured during boreal spring and autumn X. A. Padin padin@iim.csic.es M. Vázquez-Rodríguez M. Castaño A. Velo F. Alonso-Pérez J. Gago M. Gilcoto M. Álvarez P. C. Pardo M. de la Paz A. F. Ríos F. F. Pérez Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello 6, 36208 Vigo, Spain Instituto Español de Oceanografía (IEO. Vigo), Cabo Estai &ndash; Canido, Apartado 1552, 36200 Vigo, Spain Institut Mediterrani d'Estudis Avançats, CSIC-UIB, Miquel Marqués 21, 07190 Esporles, Spain A total of fourteen hydrographic cruises from 2000 to 2008 were conducted during the spring and autumn seasons between Spain and the Southern Ocean under the framework of the Spanish research project FICARAM. The underway measurements were processed and analysed to describe the meridional air-sea CO₂ fluxes (<i>F</i>CO₂) in the covered sector of the Atlantic Ocean. The data has been grouped into different biogeochemical oceanographic provinces based on thermohaline characteristics. The spatial and temporal distributions of <i>F</i>CO₂ followed expected distributions and annual trends reproducing the recent climatological &Delta;<i>f</i>CO₂ estimations with a mean difference of &minus;3 ± 18 &mu;atm (Takahashi et al., 2009). The reduction in the CO₂ saturation along the meridional FICARAM cruises represented an increase of 0.02 ± 0.14 mol m^&minus;2 yr^&minus;1 in the ocean uptake of atmospheric CO₂. The subtropical waters in both Hemispheres acted as a sink of atmospheric CO₂ during the successive spring seasons and as a source in autumn. The coarse reduction of the ocean uptake of atmospheric CO₂ observed in the North Atlantic Ocean was linked to conditions of negative phase of the North Atlantic Oscillation that prevailed during the FICARAM period. Surface waters in the North Equatorial Counter Current revealed a significant long-term decrease of sea surface salinity of &minus;0.16 ± 0.01 yr^&minus;1 coinciding with a declination of &minus;3.5 ± 0.9 &mu;atm yr^&minus;1 in the air–sea disequilibrium of CO₂ fugacity and a rise of oceanic CO₂ uptake of &minus;0.09 ± 0.03 mol m^&minus;2 yr^&minus;1. The largest CO₂ source was located in the equatorial upwelling system. These tropical waters that reached emissions of 0.7 ± 0.5 and 1.0 ± 0.7 mol m^&minus;2 y^&minus;1 in spring and autumn, respectively, showed an interannual warming of 0.11 ± 0.03 °C yr^&minus;1 and a wind speed decrease of &minus;0.58 ± 0.14 m s^&minus;1 yr^&minus;1 in spring cruises which suggest the weakening of upwelling events associated with warm El Niño – Southern Oscillation episodes. Contrary the surface waters of the Patagonian Sea behaved as an intense sink of CO₂ in March and November. The oceanic waters of the convergence of Falkland and Brazil Currents showed the strongest CO₂ absorption with a rate of &minus;5.4 ± 3.6 mol m^&minus;2 yr^&minus;1 in November. The Southern Oceans sampled in the Drake Passage behave as an average uptake rate of &minus;1.1 ± 0.9 mol m^&minus;2 yr^&minus;1 while the distal shelf of the Livingston Island acted as a slight source of CO₂ to the atmosphere. Andersson, A. J. and Mackenzie, F. T.: Shallow-water oceans: a source or sink of atmospheric CO₂? Frontiers in Ecology and Environment, 2(7), 348–353, 2004. Arístegui, J., Barton, E. D., Álvarez-Salgado, X. A., Santos, A. M. P., Figueiras, F. G., Kifani, S., Hernández-León, S., Mason, E., Mach\'u, E., and Demarcq, H.: Sub-regional ecosystem variability in the Canary Current upwelling, Prog. Oceanogr., 83, 33–48, 2009. Bakun, A. and Parrish, R. H.: Comparative studies of coastal pelagic fish reproductive habitats: the anchovy (Engraulis anchoita) of the southwestern Atlantic, ICES Journal of Marine Science: J. Conseil, 48, 343-361, 1991. Bakun, A., Field, D. B., Redondo-Rodriguez, A., and Weeks, S. J.: Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Glob. Change Biol., 16, 1213–1228, doi:10.1111/j.1365-2486.2009.02094.x, 2010. Barton, E. D.: Ocean Currents: Atlantic Eastern Boundary – Canary Current/ Portugal Current, in: Encyclopedia of Ocean Sciences, edited by: Steele, J., Thorpe S., and Turekian, K., Vol 1, pp~380–389, Academic Press, London, 2001. Battle, M., Bender, M. L., Tans, P. P., White, J. W. C., Ellis, J. T., Conway, T., and Francey, R. J.: Global carbon sinks and their variability inferred from atmospheric O₂ and $\delta $C$^13$, Science, 287, 2467–2470, 2000. Bianchi, A. A., Giulivi, C. F., and Piola, A. R.: Mixing in the Brazil-Malvinas confluence, Deep-Sea Res. Pt II, 40, 1345–1358, 1993. Bianchi, A. A., Bianucci, L., Piola, A. R., Pino, D. R., Schloss, I., Poisson, A., and Balestrini, C. F.: Vertical stratification and air-sea CO₂ fluxes in the Patagonian shelf, J. Geophys. Res.-Oceans, 110, C07003, doi:10.1029/2004JC002488, 2005. Bianchi, A. A., Pino, D. R., Perlender, H. G. I., Osiroff, A. P., Segura, V., Lutz, V., Clara, M. L., Balestrini, C. F., and Piola, A. R.: Annual balance and seasonal variability of sea-air CO₂ fluxes in the Patagonia Sea: Their relationship with fronts and chlorophyll distribution, J. Geophys. Res.-Oceans, 114, C03018, doi:10.1029/2008JC004854, 2009. Blain, S., Tréguer, P., Belviso, S., Bucciarelli, E., Denis, M., Desabre, S., Fiala, M., Martin Jézéquel, V., Le Fèvre, J., and Mayzaud, P.: A biogeochemical study of the island mass effect in the context of the iron hypothesis: Kerguelen Islands, Southern Ocean, Deep-Sea Res. Pt I, 48, 163–187, 2001. Borges, A. V., Tilbrook, B., Metzl, N., Lenton, A., and Delille, B.: Inter-annual variability of the carbon dioxide oceanic sink south of Tasmania, Biogeosciences, 5, 141–155, 2008. Canadell, J. G., Le Quéré, C., Raupach, M. R., Field, C. B., Buitenhuis, E. T., Ciais, P., Conway, T. J., Gillett, N. P., Houghton, R. A., and Marland, G.: Contributions to accelerating atmospheric CO₂ growth from economic activity, carbon intensity, and efficiency of natural sinks, P. Natl. A. Sci., 104, 10288–10293, 2007. Chavez, F. P. and Messié, M.: A comparison of Eastern Boundary Upwelling Ecosystems, Prog. Oceanogr., 83, 80–96, 2009 Chen, C. T. A. and Borges, A. V.: Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO₂, Deep-Sea Res. Pt II, 56, 578–590, doi:10.1016/j.dsr2.2009.01.001, 2009. Cooper, D. J., Watson, A. J., Ling, R. D.: Variations of $p$CO₂ along a North Atlantic shipping route (UK to Jamaica): a year of automated observations, Mar. Chem., 60, 147–164, 2008. Delille, D., Gleizon, F., and Delille, B.: Spatial and temporal variation of bacterioplankton in a sub-Antarctic coastal area (Kerguelen Archipelago). J. Marine Syst., 68, 366–380, 2007. Emery, W. J. and Dewar, J. S.: Mean temperature-salinity, salinity-depth and temperature-depth curves for the North Atlantic and the North Pacific, Prog. Oceanogr., 11, 219–305, 1982. Enfield, D. and Mayer, D.: Tropical Atlantic sea surface temperature variability and its relation to El Niño-Southern Oscillation, J. Geophys. Res., 102(C1), 929–945, 1997. Flatau, M. K., Talley, L., and Niiler, P. P.: The North Atlantic Oscillation, surface current velocities, and SST changes in the subpolar North Atlantic, J. Climatol., 16, 2355–2369, 2003. Francey, R. J., Tans, P. P., Allison, C. E., Enting, I. G., White, J. W. C., and Trolier, M.: Changes in oceanic and terrestrial carbon uptake since 1982, Nature, 373, 326–330, 1995. Froneman, P. W., McQuaid, C. D., and Laubscher, R. K.: Size-fractionated primary production sudies in the vicinity of the Subtropical Front and an adjacent warm-core south of Africa in austral winter, J. Plankton Res., 21, 2019-2035, 1999. Gordon, A. L.: Brazil-Malvinas confluence-1984, Deep-Sea Res. Pt II, 36, 359–384, 1989. Goyet, C., Adams, R., and Eischeid, G.: Observations of the CO$_2 $system properties in the tropical Atlantic Ocean. Mar. Chem., 60, 49–61, 1998. Gregg, W. W, Casey, N. W., and McClain, C. R.: Recent trends in global ocean chlorophyll, Geophys. Res. Lett., 32, L03606, doi:10.1029/2004GL021808, 2005. Grodsky, S. A., Carton, J. A., McClain, C. R.: Variability of upwelling and chlorophyll in the equatorial Atlantic, Geophys. Res. Lett., 35, L03610, doi:10.1029/2007GL032466, 2008. Gruber, N., Gloor, M., Mikaloff Fletcher, S. E., Doney, S. C., Dutkiewicz, S., Follows, M. J., Gerber, M., Jacobson, A. R., Joos, F., Lindsay, K., Menemenlis, D., Mouchet, A., Müller, S. A., Sarmiento, J. L., and Takahashi, T.: Oceanic sources, sinks, and transport of atmospheric CO₂, Global Biogeochem. Cy., 23, GB1005, doi:10.1029/2008GB003349, 2009. Guerrero, R., Acha, E., Framinan, M., and Lasta, C.: Physical oceanography of the River Plate Estuary, Cont. Shelf Res., 17, 727–742, 1997. Gurney, K. R., Law, R. M., Denning, A. S., Rayner, P. J., Pak, B. and the TransCom-3L2 modelers.: Transcom-3 inversion intercomparison: Control results for the estimation of seasonal carbon sources and sinks, Global Biogeochem. Cy., 18, GB1010, doi:10.1029/2003GB002111, 2004. Hartmann, D. L. and Lo, F.: Wave-Driven Zonal Flow Vacillation in the Southern Hemisphere, J. Atmos. Sci., 55(8), 1303–1315, 1998. Häkkinen, S. and Rhines, P. B.: Shifting surface currents in the northern North Atlantic Ocean, J. Geophys. Res.-Oceans, 114 (C04005), doi:10.1029/2008JC004883, 2009. Herbaut, C. and Houssais, M. N.: Response of the eastern North Atlantic subpolar gyre to the North Atlantic Oscillation, Geophys. Res. Lett., 36, L17607, doi:10.1029/2009GL039090, 2009. Hill, A. D., Hickey, B. M., Shillington, F. A., Strub, P. T., Brink, K. H., Barton, E., and Thomas, A. C.: Eastern ocean boundaries, Coastal segment (E), The Sea, 11, 29–65, 1998. Hooker, S. B., Rees, N. W., and Aiken, J.: An objective methodology for identifying oceanic provinces, Prog. Oceanogr., 45, 313–338, 2000. Hooker, S. B., Esaias, W. E., Feldman, G. C., Gregg, W. W., and McClain, C. R.: An overview of SeaWiFS and ocean colour, edited by: Hooker, S. B. and Firestone, E. R., NASA Technical Memo 104566, vol 1. NASA Goddard Space Flight Centre, Greenbelt, MA, p 24, 1992. Houghton, R. A.: Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850–2000, Tellus B, 55, 378–390, doi:10.1034/j.1600-0889.2003.01450.x, 2003. Hurrell, J. M.: Decadal trends in the North Atlantic oscillation regional temperatures and precipitation, Science, 269, 676–679, 1995. Ito, R. G., Schneider, T. B., and Thomas, H.: Distribution of surface fCO2 and air–sea fluxes in the Southwestern subtropical Atlantic and adjacent continental shelf, J. Marine Syst. 56, 227–242, 2005. Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., and Woollen, J.: The NCEP/NCAR reanalysis project, B. Am. Meteorol. Soc., 77, 437–471, 1996. Keeling, C. D.: Carbon dioxide in surface ocean waters, Global distribution, J. Geophys. Res., 73, 4543–4553, 1968. Keeling, C. D., Whorf, T. P., Wahlen, M., and Plicht, J.: Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980, Nature, 375, 666–670, 1995. Keeling, C. D. and Whorf, T. P.: The 1800-year oceanic tidal cycle: A possible cause of rapid climate change: Natl. A. Sci. P., 97(10), 3814–3819, 2000. Körtzinger, A., Thomas, H., Schneider, B., Gronau, N., Mintrop, L., and Duinker, J. C.: At-sea intercomparison of two newly designed underway $p$CO₂ systems – encouraging results, Mar. Chem., 52, 133–145, 1996. Labat, D., Ronchail, J., and Guyot, J. L.: Recent advances in wavelet analyses: Part 2 – Amazon, Parana, Orinoco and Congo discharges time scale variability, J. Hydrol., 314(1–4), 289–311, 2005. Latif, M. and Grötzner, A.: The equatorial Atlantic oscillation and its response to ENSO, Clim. Dynam., 16, 213–218, 2000. Lauvset, S. K., Olsen,$^ $A., Wanninkhof, R., Takahashi, T., Borges, A. V., Cai, W. -J., Skjelvan, I., Padin, X. A., Perez, F. F., Rios, A. F., Lefevre, N., Dandonneau, Y., Gonzalez-Davila, M., Johannessen, T., Körtzinger, A., Pierrot, D., Santana-Casiano, J. M., Schuster, U., Steinhoff, T., Wallace, D. and Watson, A.: North Atlantic relationships between surface $f$CO₂ and hydrography, evaluated using $f$CO₂-SST relationships, Deep Sea Res., in press, 2010. Lauthuilière, C., Echevin, V., and Lévy, M.: Seasonal and intraseasonal surface chlorophyll-a variability along the northwest African coast, J. Geophys. Res., 113, C05007. doi:10.1029/2007JC004433, 2008. Lefèvre, N.: Objective mapping of the seasonal variability of Δ$p$CO₂ in the North Atlantic Ocean, The Global Atmosphere and Ocean System, 5, 247–271, 1997. Lefèvre, N., Moore, G., Aiken, J., Watson, A., Cooper, D., and Ling, R.: Variability of $p$CO₂ in the tropical Atlantic in 1995, J. Geophys. Res., 103, 5623–5634, 1998. Lefèvre, N., Watson, A. J., Olsen, A., Ríos, A. F., Pérez, F. F., and Johannessen, T.: A decrease in the sink for atmospheric CO₂ in the North Atlantic, Geophys. Res. Lett., 31, L07306, doi:10.1029/2003GL018957, 2004. Legendre, L., Ackley, S. F., Dieckmann, G. S., Gulliksen, B., Horner, R., Hoshiai, T., Melnikov, I. A., Reeburgh, W. S., Spindler, M., and Sullivan, C. W.: Ecology of sea ice biota, Polar Biol., 12, 429–444, 1992. Longhurst, A., Sathyendranath, S., Platt, T., and Caverhill, C.: An estimate of global primary production in the ocean from satellite radiometer data, J. Plankton Res., 17, 1245–1271, 1995. Lovenduski, N. S., Gruber, N., Doney, S. C., and Lima, I. D.: Enhanced CO₂ outgassing in the Southern Ocean from a positive phase of the Southern Annular Mode, Global Biogeochem. Cy., 21(2), GB2026, doi:10.1029/2006GB002900, 2007. Lueger, H., Wanninkhof, R., Olsen, A., Triñanes, J., Johannessen, T., Wallace, D. W. R., and Körtzinger, A.: The Sea-Air CO₂ Flux in the North Atlantic Estimated From Satellite and ARGO Profiling Float Data, NOAA Tech. Memo. OAR AOML-96, 28 pp., Atlantic Oceanography and Meteorological Laboratory, NOAA, Miami, Fla, 2008. Marshall, J., Kushnir, Y., Battisti, D., Chang, P., Czaja, A., Dickson, R., Hurrell, J., McCartney, M., Saravanan, R., Visbeck, M.: North Atlantic climate variability, phenomena, impacts and mechanisms, International J. Climatol., 21, 1863–1898, 2001. McNeil, B. I., Metzl, N., Key, R. M., Matear, R. J., and Corbiere, A.: An empirical estimate of the Southern Ocean air-sea CO₂ flux, Global Biogeochem. Cy., 21, GB3011, doi:10.1029/2007GB002991, 2007. Metzl, N., Beauverger, C., Brunet, C., Goyet, C., and Poisson, A.: Surface water carbon dioxide in the southwest Indian sector of the Southern Ocean: a highly variable CO₂ source/sink region in summer, Mar. Chem., 35, 85–95, 1991. Metzl, N., Tilbrook, B., and Poisson, A.: The annual $f$CO₂ cycle and the air-sea CO₂ flux in the sub-Antarctic Ocean, Tellus B, 51, 849–861, 1999. Metzl, N.: Air-sea CO₂ fluxes in the Southern Ocean: natural and methodological variabilities, SOLAS Open Conference, Halifax, 2004. Mittelstaedt, E.: The ocean boundary along the northwest African coast: circulation and oceanographic properties at the sea surface, Prog. Oceanogr., 26, 307–355, 1991. Müller-Karger, F. E., McClain, C. R., and Richardson, P. L.: The dispersal of the Amazon's water, Nature, 333, 56–59, 1988. Nowlin, W. D. and Klinck, J. M.: The physics of the Antarctic Circumpolar Current, Geophys. Res. Lett., 24, 469–491, 1986. Olsen, A., Trinanes, J. A., and Wanninkhof, R.: Sea–air flux of CO₂ in the Caribbean Sea estimated using in situ and remote sensing data, Remote Sens. Environ., 89, 309–325, 2004. Ono, T., Saino, T., Kurita, N., and Sasaki, K.: Basin-scale extrapolation of shipboard $p$CO₂ data by using satellite SST and Chla, Int. J. Remote Sens., 25(19), 3803–3815, 2004. Osborn, T.: North Atlantic Oscillation index data, http://www.cru.uea.ac.uk/~timo/projpages/nao_update.htm, 2010. Padin, X. A., Vázquez-Rodríguez, M., Rios, A. F., and Pérez, F. F.: Atmospheric CO$_2 $ measurements and error analysis on seasonal air–sea CO₂ fluxes in the Bay of Biscay, J. Marine Syst., 66, 285–296, doi:10.1016/j.jmarsys.2006.05.010, 2007. Padin, X. A., Castro, C. G., Ríos, A. F., and Pérez, F. F.: $f$CO$_2^\rm sw$ variability in the Bay of Biscay during ECO cruises, Cont. Shelf Res., 28, 904–914, 2008. Padin, X. A., Navarro, G., Gilcoto, M., Rios, A. F., and Pérez, F. F.: Estimation of air–sea CO₂ fluxes in the Bay of Biscay based on empirical relationships and remotely sensed observations, J. Marine Syst. 75, 280–289, 2009. Patra, P. K., Maksyutov, S., Ishizawa, M., Nakazawa, T., Takahashi, T., and Ukita, J.: Interannual and decadal changes in the sea-air CO₂ flux from atmospheric CO₂ inverse modeling, Global Biogeochem. Cy., 19, GB4013, doi:10.1029/2004GB002257, 2005. Pérez, F., Padin, X. A., Pazos, Y., Gilcoto, M., Cabanas, M., Conde, P., Doval, M. D., and Farina-Busto, L.: Plankton response to weakening of the Iberian coastal upwelling, Glob. Change Biol., 16, 1258–1267, doi:10.1111/j.1365-2486.2009.02125.x, 2010. Perissinotto, R., Laubscher, R. K., and McQuaid, C. D.: Marine productivity enhancement around Bouvet and the South Sandwich Islands (Southern Ocean), Mar. Ecol. Prog.-Ser., 88, 41–53, 1992. Perissinotto, R., Lutjeharms, J. R. E., and van Ballegooyen, R. C.: Biological-physical interactions and pelagic productivity at the Prince Edward Island, Southern Ocean, J. Marine Syst., 24, 327–341, 2000. Piola, A. R. and Rivas, A. L.: Corrientes en la Plataforma Continental en Boschi, EE (ed), El Mar Argentino y sus Recursos Pesqueros, Vol 1: Antecedentes históricos de las exploraciones en el mar y las características ambientales, Instituto Nacional de Investigación y Desarrollo Pesquero, Mar del Plata, 119–132, 1997. Poisson, A., Metzl, N., Brunet, C., Schauer, B., Bres, B., Ruíz-Pino, D., and Louanchi, F.: Variability of sources and sinks of CO₂ in the Western Indian and Southern Oceans during the year 1991, J. Geophys. Res., 98, 22759–22778, 1993. Richardson, P. L. and McKee, T. K.: Average seasonal variation of the Atlantic Equatorial Currents from historical ship drifts, J. Phys. Oceanogr., 14, 1226–1238, 1984. Richardson, P. and Reverdin, G.: Seasonal Cycle of Velocity in the Atlantic North Equatorial Countercurrent as Measured by Surface Drifters, Current Meters, and Ship Drifts, J. Geophys. Res., 92(C4), 3691–3708, 1987. Romero, S. L., Piola, A. R. Charo, M., and García, C. E.: Chlorophylla variability off Patagonia based on SeaWiFS data, J. Geophys. Res., 111, C05021, doi:10.1029/2005JC003244, 2006. Ríos, A. F., Pérez, F. F., and Fraga, F.: Water masses in the upper and middle North Atlantic Ocean east of the Azores, Deep-Sea Res. Pt II, 39, 645–658, 1992. Roy, C. and Reason, C.: ENSO related modulation of coastal upwelling in the eastern Atlantic, Prog. Oceanogr., 49, 245–255, 2001. Roy, R., Rayner, P., Matear, R., and Francey, R.: Southern hemisphere ocean CO₂ uptake: reconciling atmospheric and oceanic estimates, Tellus B., 55(2), 701–710, 2003. Sabine, C. L., Feely, R. A., Gruber, N., Key, R. M., Lee, K., Bullister, J. L., Wanninkhof, R., Wong, C. S., Wallace, D. W. R., Tilbrook, B., Millero, F. J., Peng, T. H., Kozyr, A., Ono, T., and Ríos, A. F.: The oceanic sink for anthropogenic CO₂, Science, 305, 5682, 367–371, 2004. Santana-Casiano, J. M., González-Dávila, M., Rueda, M. J., Llinás, O., and González-Dávila, E. F.: The interannual variability of oceanic CO₂ parameters in the northeast Atlantic subtropical gyre at the ESTOC site, Global Biogeochem. Cy., 21, GB1015, doi:10.1029/2006GB002788, 2007. Santos, A., Kazmin, A., and Peliz, A.: Decadal changes in the Canary upwelling system as revealed by satellite observations: Their impact on productivity, J. Marine Res., 63, 359–379, 2005. Sarmiento, J. L. and Gruber, N.: Sinks for anthropogenic carbon, Physics Today, 55, 30–36, 2002. Schuster, U. and Watson, A. J.: A variable and decreasing sink for atmospheric CO₂ in the North Atlantic, J. Geophys. Res., 112, C11006, doi:10.1029/2006JC003941, 2007. Schuster, U., Watson, A. J., Bates, N., Corbière, A., Gonzalez-Davila, M., Metzl, N., Pierrot, D., and Santana-Casiano, M.: Trends in North Atlantic sea surface $f$CO₂ from 1990 to 2006, Deep-Sea Res. Pt II, 56, 620–629, 2009. Siedler, G., Laurence, A., and Müller, T. J.: Meddies and decadal changes at the Azores Front from 1980 to 2000, Deep Sea Res. Pt II, 52, 583–604, 2005. Siegenthaler, U. and Sarmiento, J. L.: Atmospheric carbon dioxide and the ocean, Nature, 365, 119–125, 1993. Solomon, S., Qin, D., and Manning, M.: Climate Change 2007: The Physical Science Basis, Fourth IPCC Report, Cambridge Univ. Press, Cambridge, U. K., 2007. Subramaniam, A., Yager, P. L., Carpenter, E. J., Mahaffey, C., Björkman, K., Cooley, S., Kustka, A. B., Montoya, J. P., Sañudo-Wilhelmy, S. A., and Shipe, R.: From the Cover: Amazon River enhances diazotrophy and carbon sequestration in the tropical North Atlantic Ocean, P. Natl. Acad. Sci. USA, 105, 10460–10465, 2008. Takahashi, T.: Carbon dioxide in the atmosphere and in Atlantic ocean water, J. Geophys. Res., 66, 477–494, 1961. Takahashi, T., Olafsson, J., Goddard, J. G., Chipman, D. W., and Sutherland, S. C.: Seasonal variation of CO₂ and nutrients in the high-latitude surface oceans: a comparative study, Global Biogeochem. Cy., 7, 843–878, 1993. Takahashi, T., Sutherland, S. C., Wanninkhof, R., Sweeney, C., Feely, R. A., Chipman, D. W., Hales, B., Friederich, G., Chavez, F., Sabine, C., Watson, A. J., Bakker, D. C., Schuster, U., Metzl, N., Yoshikawa-Inoue,H., Ishii, M., Midorikawa, T., Nojiri, Y., K\" ortzinger, A., Steinhoff, T., Hoppema, M., Olafsson, J., Arnarson, T. S., Tilbrook, B., Johannessen, T., Olsen, A.,, and Bellerby, R., Wong, C. S., Delille, B., Bates, N. R., and de Baar, H. J. W.: Climatological mean and decadal change in surface ocean $p$CO₂, and net sea-air CO₂ flux over the global oceans, Deep-Sea Res. Pt II, 56, doi:10.1016/j.dsr2.2008.12.009, 2009. Ternon, J. F., Oudot, C., Dessier, A., and Diverres, D.: A seasonal tropical sink for atmospheric CO₂ in the Atlantic ocean: the role of the Amazon River discharge, Mar. Chem. 68(3), 183–201, 2000. Thomas, H., Bozec, Y., Elkalay, K., and De Baar, H. J. W.: Enhanced open ocean storage of CO₂ from shelf sea pumping, American Association for the Advancement of Science, 1005–1008, 2004. Thomas, H., Prowe, A. E., Lima, I. D., Doney, S. C., Wanninkhof, R., Greatbatch, R. J., Schuster, U., and Corbière, A.: Changes in the North Atlantic Oscillation influence CO₂ uptake in the North Atlantic over the past two decades, Global Biogeochem. Cy., 22, GB4027, doi:10.1029/2007GB003167, 2008. Ullman, D. J., McKinley, G. A., Bennington, V., and Dutkiewicz, S.: Trends in the North Atlantic carbon sink: 1992–2006, Global Biogeochem. Cy., 23, GB4011, doi:10.1029/2008GB003383, 2009. Wanninkhof, R.: Relationship between wind speed and gas exchange over the ocean, J. Geophys. Res., 97, 7373–7382, 1992. Wanninkhof, R., Olsen, A., and Trinanes, J.: Air–sea CO₂ fluxes in the Caribbean Sea from 2002–2004. J. Marine Syst. 66(1), 272–284, 2007. Weiss, R. F.: Carbon dioxide in water and seawater: the solubility of non-ideal gas, Mar. Chem., 2, 203–215, 1974. Wolf-Gladrow, D. A., Riebesell, U., Burkhardt, S., and Bijma, J.: Direct effects of CO₂ concentration on growth and isotopic composition of marine plankton, Tellus B, 51, 461–476, 1999. Zeng, N.: Seasonal cycle and interannual variability in the Amazon hydrologic cycle, J. Geophys. Res., 104(D8), 9097–9106, 1999.