Ocean Science www.ocean-sci.net 1812-0784 1812-0792 2 2 2006 10.5194/os-2-137-2006 http://www.ocean-sci.net/2/137/2006/ http://www.ocean-sci.net/2/137/2006/os-2-137-2006.html http://www.ocean-sci.net/2/137/2006/os-2-137-2006.pdf 137 146 2006-10-10 Tropical extra-tropical thermocline water mass exchanges in the Community Climate Model v.3 Part I: the Atlantic Ocean I. Wainer wainer@usp.br A. Lazar A. Solomon Department of Physical Oceanography, University of São Paulo, São Paulo, Brazil Laboratoire d'Océanographie Dynamique et de Climatologie (LODYC), Paris, France National Oceanic Atmospheric Administration-Cooperative Institute Research Environmental Sciences (NOAA-CIRES) Climate Diagnostics Center, USA The climatological annual mean tropical-extra-tropical pathways of thermocline waters in the Atlantic Ocean are investigated with the NCAR CCSM numerical coupled model. Results from three numerical experiments are analyzed: Two are fully coupled runs with different spatial resolution (T42 and T85) for the atmospheric component. The third numerical experiment is an ocean-only run forced by NCEP winds and fluxes. Results show that the different atmospheric resolutions have a significant impact on the subduction pathways in the Atlantic because of how the wind field is represented. These simulation results also show that the water subducted at the subtropics reaching the EUC is entirely from the South Atlantic. The coupled model ability to simulate the STCs is discussed. Alexander, M., Yin, J., Branstator, G., Capotondi, A., Cassou, C., Cullather, R., Kwon, Y., Norris, J., Scott, J., and Wainer, I.: Extratropical Ocean-Atmosphere Variability in CCSM3, J. Clim., 19, 2496–2525, 2006. Blanke, B., Arhan, M., Madec, G., and Roche, S.: Warm water paths in the equatorial Atlantic as diagnosed with a general circulation model, J. Phys. Oceanogr., 29, 2753–2768, 1999. Bonhoure, D., Rowe, E., Mariano, A., and Ryan, E.: The South Equatorial Current System, Internet: http://oceancurrents.rsmas.miami.edu/atlantic/south-equatorial.html, 2003. Briegleb, B. P., Bitz, C. M., Hunke, E. C., Lipscomb, W. H., Holland, M. M., Schramm, J. L., and Moritz, R. E.: Scientific description of the sea ice component in the Community Climate System Model, Version Three, NCAR Tech. Note NCAR/TN- 463+STR 70 pp, 2004. Collins, W., Rasch, P., Boville, B., Hack, J., McCaa, J., Williamson, D., Briegleb, B., Bitz, C., Lin, S., and Zhang, M.: The Formulation and Atmospheric Simulation of the Community Atmosphere Model: CAM3, J. Clim., 29, 2144–2161, 2005. Collins, W., Blackmon, M., Bitz, C., Bonan, G. B., Bretherton, C. S., Carton, J. A., Chang, P., Doney, S., Hack, J. J., Kiehl, J. T., Henderson, T., Large, W. G., McKenna, D., Santer, B. D., and Smith, R.: The Community Climate System Model: CCSM3, J. Clim., 19, 2122–2143, 2006. Cushman-Roisin, B.: Dynamics of the Oceanic Surface Mixed Layer, Hawaii Inst. of Geophys., 1987. Davey, M., Huddleston, M., Sperber, K., Braconnot, P., Bryan, F., Chen, D., Colman, R., Cooper, C., Cubasch, U., Delecluse, P., DeWitt, D., Fairhead, L., Flato, G., Gordon, C., Hogan, T., Ji, M., Kimoto, M., Kitoh, A., Knutson, T., Latif, M., Treut, H. L., Li, T., Manabe, S., Mechoso, C., Meehl, G., Power, S., Roeckner, E., Terray, L., Vintzileos, A., Voss, R., Wang, B., Washington, W., Yoshikawa, I., Yu, J., Yukimoto, S., Zebiak, S., and Danabasoglu, G.: STOIC: a study of coupled model climatology and variability in tropical ocean regions, Clim. Dyn., 18, 403–420, 2002. Dickinson, R., Oleson, K., Bonan, G., Hoffman, F., Vertenstein, P. T. M., Yang, Z.-L., and Zeng, X.: The Community Land Model and Its Climate Statistics as a Component of the Community Climate System Model, J. Clim., 19, 2302–2324, 2006. Fratantoni, D. W. J., Townsend, T., and Hurlburt, H.: Low-Latitude Circulation and Mass Transport Pathways in a Model of the Tropical Atlantic Ocean, J. Phys. Oceanogr., 30, 1944–1966, 2000. Gent, P. and McWilliams, J.: Isopycnal mixing in ocean circulation models, J. Phys. Oceanogr., 20, 150–155, 1990. Grodsky, S. A. and Carton, J.: Surface drifter pathways originating in the equatorial Atlantic cold tongue, Geophys. Res. Lett., 29(23), 2147–2151, 2002. Harper, S.: Thermocline ventilation and pathways of tropical-subtropical water mass exchange, Tellus, 52A, 330–345, 2002. Hazeleger, W., de Vries, P., and Friocourt, Y.: Sources of the Equatorial Undercurrent in the Atlantic in a High-Resolution Ocean Model, J. Phys. Oceanogr., 33, 677–693, 2003. Inui, T., Lazar, A., Malanotte-Rizzoli, P., and Busalacchi, A.: Wind stress effects on the Atlantic subtropical-tropical circulation, J. Phys. Oceanogr., 32(8), 2257–2276, 2002. Kalnay, E., Kanamitsu, M., Kistler, Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Leetmaa, A., Reynolds, R., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K. C., Ropelewski, C., Wang, J., Jenne, R., and Joseph, D.: The NCEP/NCAR 40-year reanalysis project, Bull. Am. Meteorol. Soc., 77, 437–471, 1996. Large, W. and Danabasoglu, G.: Attribution and Impacts of Upper-Ocean Biases in CCSM3, J. Clim., 19, 2325–2346, 2006. Large, W., McWilliams, J., and Doney, S. C.: Oceanic vertical mixing: A review and a model with a nonlocal boundary layer parameterization, Rev. Geophys., 32, 363–403, 1994. Lazar, A., Inui, T., Busalacchi, A., Malanotte-Rizzoli, P., and Wang, L.: Seasonality of the ventilation of the tropical Atlantic thermocline, J. Geophys. Res., 107, 181–187, 2002. Levitus, S., Antonov, J., Boyer, T., and Stephens, C.: Warming of the world ocean., Science, 287, 2225–2229, 2000. Liu, Z. and Philander, S.: How different wind stress patterns affect the tropical-subtropical circulations of the upper ocean, J. Phys. Oceanogr., 25, 449–462, 1995. Luyten, J., Pedlosky, J., and Stommel, H.: The ventilated thermocline, J. Phys. Oceanogr., 13, 292–309, 1983. Malanotte-Rizzoli, P., Hedstrom, K., Arango, H., and Haidvogel, D.: Water mass pathways between the subtropical and tropical ocean in a climatological simulation of the North Atlantic ocean circulation, Dyn. Atmos. Oceans, 32, 331–371, 2000. Metcalf, W. and Stalcup, M.: Origin of the Atlantic Equatorial Undercurrent, J. Geophys. Res., 72, 4959–4875, 1967. Molinari, R., Bauer, S., Snowden, D., Johnson, G., Bourles, B., Gouriou, Y., and Mercier, H.: A Comparison of kinematic evidence for tropical cells in the Atlantic and Pacific oceans, Elsevier Oceanographic Series, 2003. Norris, J. R. and Weaver, C. P.: Improved techniques for evaluating GCM cloudiness applied to the NCAR CCM3, J. Clim., 14, 2540–2550, 2001. Schott, F., Fischer, J., and Stramma, L.: Transports and pathways of the upper-layer circulation in the western tropical Atlantic, J. Phys. Oceanogr., 28, 1904–1918, 1998. Schott, F. A., McCreary, J. P., and Johnson, G. C.: Shallow overturning circulations of the tropical-subtropical oceans, Ocean-Atmosphere Interaction and Climate Variability, in: AGU Geophys. Monogr., edited by: Wang, C., Xie, S.-P., and Carton, J. A., Amer. Geophys. Union Geophysical Monograph, 147, 393–405, 2004. Smith, R. and Gent, P.: Reference manual for the Parallel Ocean Program (POP): Ocean component of the Community Climate System Model (CCSM2.0 and CCSM3.0), Los Alamos National Laboratory Technical Report LA-UR-02-2484, 2002. Smith, R. and McWilliams, J.: Anisotropic horizontal viscosity for ocean models, Oc. Model, 5, 129–156, 2003. Snowden, D. and Molinari, R.: Subtropical cells in the Atlantic Ocean: An observational summary, Elsevier Oceanography Series, 68 (ISBN 0-444-51267-5), 2003. Zhang, D., McPhaden, M., and Johns, W.: Interior Pycnocline Transports in the Atlantic Subtropical Cells, Exchanges, 25, 1–3, 2002. Zhang, D., McPhaden, M., and Johns, W.: Observational evidence for flow between the Subtropical and Tropical Atlantic: the Atlantic Subtropical Cells, J. Phys. Oceanogr., 33, 1783–1797, 2003.