Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 1 2008 10.5194/bg-5-141-2008 http://www.biogeosciences.net/5/141/2008/ http://www.biogeosciences.net/5/141/2008/bg-5-141-2008.html http://www.biogeosciences.net/5/141/2008/bg-5-141-2008.pdf 141 155 2008-02-06 Inter-annual variability of the carbon dioxide oceanic sink south of Tasmania A. V. Borges alberto.borges@ulg.ac.be B. Tilbrook N. Metzl A. Lenton B. Delille Unité d'Océanographie Chimique, Interfacultary Center for Marine Research, Université de Liège, Institut de Physique (B5), 4000 Liège, Belgium Wealth from Oceans Flagship, Commonwealth Scientific and Industrial Research Organisation, and Antarctic Climate and Ecosystem Cooperative Research Centre, PO Box 1538, Hobart, TAS 7001, Australia Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Institut Pierre Simon Laplace, CNRS-UMR 7159, Université Pierre et Marie Curie, Case 100, 4 Place Jussieu, 75252 Paris Cedex 5, France We compiled a large data-set from 22 cruises spanning from 1991 to 2003, of the partial pressure of CO₂ (pCO₂) in surface waters over the continental shelf (CS) and adjacent open ocean (43° to 46° S; 145° to 150° E), south of Tasmania. Climatological seasonal cycles of pCO₂ in the CS, the subtropical zone (STZ) and the subAntarctic zone (SAZ) are described and used to determine monthly pCO₂ anomalies. These are used in combination with monthly anomalies of sea surface temperature (SST) to investigate inter-annual variations of SST and pCO₂. Monthly anomalies of SST (as intense as 2°C) are apparent in the CS, STZ and SAZ, and are indicative of strong inter-annual variability that seems to be related to large-scale coupled atmosphere-ocean oscillations. Anomalies of pCO₂ normalized to a constant temperature are negatively related to SST anomalies. A reduced winter-time vertical input of dissolved inorganic carbon (DIC) during phases of positive SST anomalies, related to a poleward shift of westerly winds, and a concomitant local decrease in wind stress is the likely cause of the negative relationship between pCO₂ and SST anomalies. The observed pattern is an increase of the sink for atmospheric CO₂ associated with positive SST anomalies, although strongly modulated by inter-annual variability of wind speed. Assuming that phases of positive SST anomalies are indicative of the future evolution of regional ocean biogeochemistry under global warming, we show using a purely observational based approach that some provinces of the Southern Ocean could provide a potential negative feedback on increasing atmospheric CO₂. Bates, N. R.: Interannual variability of the oceanic CO₂ sink in the subtropical gyre of the North Atlantic Ocean over the last 2 decades, J. Geophys. Res., 112, C09013, doi:10.1029/2006JC003759, 2007. Behera, S. K. and Yamagata, T.: Subtropical SST dipole events in the southern Indian Ocean, Geophys. Res. Let., 28(2), 327–330, 2001. Belkin, I. M. and Gordon, A. L.: Southern Ocean fronts from the Greenwich meridian to Tasmania, J. Geophys. Res., 101(C2), 3675–3696, 1996. Bopp, L., Monfray, P., Aumont, O., Dufresne, J. L., Le Treut, H., Madec, G., Terray, L., and Orr, J. C.: Potential impact of climate change on marine export production, Global Biogeochem. Cy., 15(1), 81–99, 2001. Boyd, P. W., Crossley, A. C., DiTullio, G. R., Griffiths, F. B., Hutchins, D. A., Queguiner, B., Sedwick, P. N., and Trull T. W.: Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project, J. Geophys. Res., 106(C12), 31 573–31 583, 2001. Brévière, E., Metzl, N., Poisson, A., and Tilbrook, B.: Changes of the oceanic CO₂ sink in the Eastern Indian sector of the Southern Ocean, Tellus B, 58(5), 438–446, 2006. Brix, H., Gruber, N., and Keeling, C. D.: Interannual variability of the upper ocean carbon cycle at station ALOHA near Hawaii, Global Biogeochem. Cy., 18, GB4019, doi:10.1029/2004GB002245, 2004. Cai, W., Shi, G., Cowan, T., Bi, D., and Ribbe J.: The response of the Southern Annular Mode, the East Australian Current, and the southern mid-latitude ocean circulation to global warming, Geophys. Res. Lett., 32, L23706, doi:10.1029/2005GL024701, 2005. Condie, S. A. and Dunn, J. R.: Seasonal characteristics of the surface mixed layer in the Australasian region: implications for primary production regimes and biogeography, Mar. Freshwater Res., 57, 569–590, 2006. Copin-Montégut, C.: A new formula for the effect of temperature on the partial pressure of carbon dioxide in seawater, Mar. Chem., 25(1), 29–37, 1988. Copin-Montégut, C.: A new formula for the effect of temperature on the partial pressure of carbon dioxide in seawater, Corrigendum, Mar. Chem., 27(1–2), 143–144, 1989. Corbière, A., Metzl, N., Reverdin, C., and Takahashi, T.: Interannual and decadal variability of the oceanic carbon sink in the North Atlantic subpolar gyre, Tellus B, 59(2), 168–178, 2007. Dore, J. E., Lukas, R., Sadler, D. W., and Karl, D. M.: Climate-driven changes to the atmospheric CO₂ sink in the subtropical North Pacific Ocean, Nature, 424(6950), 754–757, 2003. Feely, R. A., Boutin, J., Cosca, C. E., Dandonneau, Y., Etcheto, J., Inoue, H. Y., Ishii, M., Le Quéré, C., Mackey, D. J., McPhaden, M., Metzl, N., Poisson, A., and Wanninkhof, R.: Seasonal and interannual variability of CO₂ in the equatorial Pacific, Deep-Sea Res. II, 49(13–14), 2443–2469, 2002. Feely, R. A., Takahashi, T., Wanninkhof, R., Mcphaden, M. J., Cosca, C. E., Sutherland, S. C., and Carr, M. E.: Decadal variability of the air-sea CO₂ fluxes in the equatorial Pacific Ocean, J. Geophys. Res., 111(C8), C08S90, doi:10.1029/2005JC003129, 2006. Frankignoulle, M., Borges, A. V., and Biondo, R.: A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments, Water Res., 35(5), 1344–1347, 2001. Goyet, C., Beauverger, C., Brunet, C., and Poisson, A.: Distribution of carbon dioxide partial pressure in surface waters of the Southwest Indian Ocean, Tellus B, 43(1), 1–11, 1991. Gruber, N., Keeling, C. D., and Bates, N. R.: Interannual variability in the North Atlantic Ocean carbon sink, Science, 298(5602), 2374–2378, 2002. Hall, A. and Visbeck, M.: Synchronous variability in the southern hemisphere atmosphere, sea ice, and ocean resulting from the annular mode, J. Climate, 15(21), 3043–3057, 2002. Hamilton, L. J.: Structure of the Subtropical Front in the Tasman Sea, Deep-Sea Res. I, 53(12), 1989–2009, 2006. Harris, G., Nilsson, C., Clementson, L., and Thomas, D.: The water masses of the east-coast of Tasmania - seasonal and interannual variability and the influence on phytoplankton biomass and productivity, Aust. J. Mar. Freshwater. Res., 38(5), 569–590, 1987. Harris, G. P., Griffiths, F. B., Clementson, L. A., Lyne, V., and Vanderdoe, H.: Seasonal and interannual variability in physical processes, nutrient cycling and the structure of the food-chain in tasmanian shelf waters, J. Plankton Res., 13(S1), 109–131, 1991. Hartmann, D. L. and Lo, F.: Wave-driven zonal flow vacillation in the Southern Hemisphere, J. Atmos. Sci., 55(8), 1303–1315, 1998. Inoue, H. Y. and Ishii, M.: Variations and trends of CO₂ in the surface seawater in the Southern Ocean south of Australia between 1969 and 2002, Tellus B, 57(1), 58–69, 2005. Jabaud-Jan, A., Metzl, N., Brunet, C., Poisson, A., and Schauer, B.: Interannual variability of the carbon dioxide system in the southern Indian Ocean (20° S–60° S): The impact of a warm anomaly in austral summer 1998, Global Biogeochem. Cy,, 18(1), GB1042, doi:10.1029/2002GB002017, 2004. Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K. C., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds, R., Jenne, R., and Joseph, D.: The NCEP/NCAR 40-year reanalysis project, B. Am. Meteorol. Soc., 77(3), 437–471, 1996. Körtzinger, A., Mintrop, L., Wallace, D. W. R., Johnson, K. M., Neill, C., Tilbrook, B., Towler, P., Inoue, H. Y., Ishii, M., and Shaffer, G.: The international at-sea intercomparison of fCO₂ systems during the R/V Meteor Cruise 36/1 in the North Atlantic Ocean, Mar. Chem., 72(2–4), 171–192, 2000. Le Quéré, C., Orr, J. C., Monfray, P., Aumont, O., and Madec, G.: Interannual variability of the oceanic sink of CO₂ from 1979 through 1997, Global Biogeochem. Cy., 14(4), 1247–1265, 2000. Le Quéré, C., Bopp, L., and Tegen, I.: Antarctic circumpolar wave impact on marine biology: A natural laboratory for climate change study, Geophys. Res. Let., 29(10), 1407, 10.1029/2001GL014585, 2002. Le Quéré, C., Aumont, O., Monfray, P., and Orr, J.: Propagation of climatic events on ocean stratification, marine biology, and CO₂: Case studies over the 1979-1999 period, J. Geophys. Res., 108(C12), 3375, doi:10.1029/2001JC000920, 2003. Le Quéré, C., Rödenbeck, C., Buitenhuis, E.T., Conway, T. J., Langenfelds, R., Gomez, A., Labuschagne, C., Ramonet, M., Nakazawa, T., Metzl, N., Gillett, N., Heimann, M.: Saturation of the Southern Ocean CO₂ sink due to recent climate change, Science, 316(5832), 1735–1738, 2007 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. Let., 31(7), L07306, doi:10.1029/2003GL018957, 2004. Lenton, A., and Matear, R. J.: Role of the Southern Annular Mode (SAM) in Southern Ocean CO₂ uptake, Global Biogeochem. Cy., 21, GB2016, doi:10.1029/2006GB002714, 2007. Lenton, A., Matear, R. J., and Tilbrook, B.: Observational strategy to constrain the annual air-sea flux of CO₂ in the Southern Ocean, Global Biogeochem. Cy., 20, GB4010, doi:10.1029/GB002620, 2006. Li, Z. X.: Influence of Tropical Pacific El Niño on the SST of the Southern Ocean through atmospheric bridge, Geophys. Res. Let., 27(21), 3505–3508, 2000. Lovenduski, N. S. and Gruber, N.: Impact of the Southern Annular Mode on Southern Ocean circulation and biology, Geophys. Res. Let., 32(11), L11603, doi:10.1029/2005GL022727, 2005. 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, GB2026, doi:10.1029/2006GB002900, 2007. Louanchi, F., Metzl, N., and Poisson, A.: Modelling the monthly sea surface fCO₂ fields in the Indian Ocean, Mar. Chem., 55(3–4), 265–279, 1996. Louanchi, F. and Hoppema, M.: Interannual variations of the Antarctic Ocean CO₂ uptake from 1986 to 1994, Mar. Chem., 72(2–4), 103–114, 2000. Matear, R. J. and Hirst, A. C.: Climate change feedback on the future oceanic CO₂ uptake, Tellus B, 51(3), 722–733, 1999. 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(1–2), 85–95, 1991. Metzl, N., Poisson, A., Louanchi, F., Brunet, C., Schauer, B., and Brès, B.: Spatio-temporal distribution of air-sea fluxes of CO₂ in the Indian and Antarctic Ocean, Tellus B, 47(1–2), 56–69, 1995. Metzl, N., Louanchi, F., and Poisson, A.: Seasonal and interannual variations of sea surface carbon dioxide in the subtropical Indian Ocean, Mar. Chem., 60(1–2), 131–146, 1998. Metzl, N., Tilbrook, B., and Poisson, A.: The annual fCO₂ cycle and the air-sea CO₂ flux in the sub-Antarctic Ocean, Tellus B, 51(4), 849–861, 1999. Metzl, N., Brunet,C., Jabaud-Jan, A., Poisson,A., and Schauer,B.: Summer and winter air-sea CO₂ fluxes in the Southern Ocean, Deep-Sea Res. I, 53(9), 1548–1563, 2006. Midorikawa, T., Ishii, M., Nemoto, K., Kamiya, H., Nakadate, A., Masuda, S., Matsueda, H., Nakano, T., and Inoue, H.Y.: Interannual variability of winter oceanic CO₂ and air-sea CO₂ flux in the western North Pacific for 2 decades, J. Geophys. Res., 111(C7), L05612, doi:10.1029/2004GL021952, 2006. Morrow, R., Valladeau, G., and Sallee, J.-B.: Observed subsurface signature of Southern Ocean sea level rise, Prog. Oceanogr., in press, 2007. Poisson, A., Metzl, N., Brunet, C., Schauer, B., Brès, B., Ruiz-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(C12), 22 759–22 778, 1993. Reynolds, R. W., Rayner, N. A., Smith, T. M., Stokes, D. C., and Wang, W. Q.: An improved in situ and satellite SST analysis for climate, J. Climate, 15(13), 1609–1625, 2002. Ridgway, K. R.: Long-term trend and decadal variability of the southward penetration of the East Australian Current, Geophys. Res. Lett., 34, L13613, doi:10.1029/2007GL030393, 2007. Rintoul, S. R. and Sokolov, S.: Baroclinic transport variability of the Antarctic Circumpolar Current south of Australia (WOCE repeat section SR3), J. Geophys. Res., 106(C2), 2815–2832, 2001. Rintoul, S. R. and Trull, T. W.: Seasonal evolution of the mixed layer in the Subantarctic Zone south of Australia, J. Geophys. Res., 106(C12), 31 447–31 462, 2001. Roemmich, D., Gilson, J., Davis, R., Sutton, P., Wijffels, S., and Riser, S.: Decadal spinup of the South Pacific Subtropical Gyre, J. Phys. Oceanogr., 37, 162–173, 2007. Sabine, C. L., Feely, R. A., 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 Rios, A. F.: The oceanic sink for anthropogenic CO₂, Science, 305(5682), 367–371, 2004. Sigman, D. M. and Boyle, E. A.: Glacial/interglacial variations in atmospheric carbon dioxide, Nature, 407(6806), 859–869, 2000. Smith, W. H. F. and Sandwell, D. T.: Global sea floor topography from satellite altimetry and ship depth soundings, Science, 277(5334), 1956–1962, 1997. Sokolov, S. and Rintoul, S.: Structure of the Southern Ocean fronts at 140° E, J. Mar. Syst., 37(1), 151–184, 2002. Takahashi, T., Sutherland, S. C., Sweeney, C., Poisson, A., Metzl, N., Tilbrook, B., Bates, N. R., Wanninkhof, R., Feely, R. A., Sabine, C., Olafsson, J., and Nojiri, Y.: Global sea-air CO₂ flux based on climatological surface ocean pCO₂, and seasonal biological and temperature effects, Deep-Sea Res. II, 49(9–10), 1601–1622, 2002. Takahashi, T., Sutherland, S. C., Feely, R. A., and Wanninkhof, R.: Decadal change of the surface water pCO₂ in the North Pacific: A synthesis of 35 years of observations, J. Geophys. Res., 111(C7), C07S05, doi:10.1029/2005JC003074, 2006. Thompson, D. and Wallace, J.: Annular modes in the extratropical circulation. Part I. Month to-month variability, J. Climate, 13, 1000–1016, 2000. Toggweiler, J. R.: Variation of atmospheric CO₂ by ventilation of the ocean's deepest water, Paleoceanography, 14(5), 571–588, 1999. Toggweiler, J. R., Russell, J. L., and Carson, S. R.: Midlatitude westerlies, atmospheric CO₂, and climate change during the ice ages, Paleoceanography, 21, PA2005, doi:10.1029/2005PA001154, 2006. Verdy, A., Marshall, J., and Czaja, A.: Sea surface temperature variability along the path of the Antarctic Circumpolar Current, J. Phys. Oceanogr., 36, 1317–1331, 2006. Verdy, A., Dutkiewicz, S., Follows, M. J., Marshall, J., and Czaja, A.: Carbon dioxide and oxygen fluxes in the Southern Ocean: Mechanisms of interannual variability, Global Biogeochem. Cy., 21, GB2020, doi:10.1029/2006GB002916, 2007. Wanninkhof, R.: Relationship between wind speed and gas exchange over the ocean, J. Geophys. Res., 97(C5), 7373–7382, 1992. Watson, A. J. and Naveira Garabato, A. C.: The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO₂ change, Tellus B, 58(1), 73–87, 2006. Weiss, R. F.: Carbon dioxide in water and seawater: the solubility of a non-ideal gas, Mar. Chem., 2(3), 203–215, 1974. Weiss, R. F. and Price, B. A.: Nitrous oxide solubility in water and seawater, Mar. Chem., 8(4), 347–359, 1980.