Ocean Response and Feedback to the SST Dipole in the Tropical Atlantic

Terrence M. Joyce Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Search for other papers by Terrence M. Joyce in
Current site
Google Scholar
PubMed
Close
,
Claude Frankignoul Pierre et Marie Curie University, Paris, France

Search for other papers by Claude Frankignoul in
Current site
Google Scholar
PubMed
Close
,
Jiayan Yang Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

Search for other papers by Jiayan Yang in
Current site
Google Scholar
PubMed
Close
, and
Helen E. Phillips Commonwealth Scientific and Industrial Research Organisation, Hobart, Tasmania, Australia

Search for other papers by Helen E. Phillips in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The equatorial SST dipole represents a mode of climate variability in the tropical Atlantic Ocean that is closely tied to cross-equatorial flow in the atmosphere, from the cold to the warm hemisphere. It has been suggested that this mode is sustained by a positive feedback of the tropical winds on the cross-equatorial SST gradient. The role, if any, of the tropical ocean is the focus of this investigation, which shows that at the latitudes of the SST signal (centered on 10°N/S) there is a weak positive feedback suggested in data from the last half century, that the cross-equatorial wind stress is closely coupled to this SST gradient on monthly time scales with no discernable lag, and that the period from January to June is the most active period for coupling. Northward (southward) anomalies of cross-equatorial wind stress are associated with a substantial negative (positive) wind stress curl. This wind system can thus drive a cross-equatorial Sverdrup transport in the ocean from the warm to the cold side of the equator (opposite the winds) with a temporal lag of only a few months. The oceanic observations of subsurface temperature and a numerical model hindcast also indicate a clear relationship between this mode of wind-driven variability and changes in the zonal transport of the North Equatorial Countercurrent. It is estimated that the time-dependent oceanic flow is capable of providing a significant contribution to the damping of the SST dipole but that external forcing is essential to sustaining the coupled variability.

Corresponding author address: Terrence M. Joyce, Woods Hole Oceanographic Institution, 360 Woods Hole Rd., MS 21, Woods Hole, MA 02543. Email: tjoyce@whoi.edu

Abstract

The equatorial SST dipole represents a mode of climate variability in the tropical Atlantic Ocean that is closely tied to cross-equatorial flow in the atmosphere, from the cold to the warm hemisphere. It has been suggested that this mode is sustained by a positive feedback of the tropical winds on the cross-equatorial SST gradient. The role, if any, of the tropical ocean is the focus of this investigation, which shows that at the latitudes of the SST signal (centered on 10°N/S) there is a weak positive feedback suggested in data from the last half century, that the cross-equatorial wind stress is closely coupled to this SST gradient on monthly time scales with no discernable lag, and that the period from January to June is the most active period for coupling. Northward (southward) anomalies of cross-equatorial wind stress are associated with a substantial negative (positive) wind stress curl. This wind system can thus drive a cross-equatorial Sverdrup transport in the ocean from the warm to the cold side of the equator (opposite the winds) with a temporal lag of only a few months. The oceanic observations of subsurface temperature and a numerical model hindcast also indicate a clear relationship between this mode of wind-driven variability and changes in the zonal transport of the North Equatorial Countercurrent. It is estimated that the time-dependent oceanic flow is capable of providing a significant contribution to the damping of the SST dipole but that external forcing is essential to sustaining the coupled variability.

Corresponding author address: Terrence M. Joyce, Woods Hole Oceanographic Institution, 360 Woods Hole Rd., MS 21, Woods Hole, MA 02543. Email: tjoyce@whoi.edu

Save
  • Capotondi, A., and M. A. Alexander, 2001: Rossby waves in the tropical North Pacific and their role in decadal thermocline variability. J. Phys. Oceanogr, 31 , 34963515.

    • Search Google Scholar
    • Export Citation
  • Carton, J. A., X. Cao, B. S. Giese, and A. M. da Silva, 1996: Decadal and interannual SST variability in the tropical Atlantic. J. Phys. Oceanogr, 26 , 11651175.

    • Search Google Scholar
    • Export Citation
  • Carton, J. A., M. Chepurin, X. Cao, and B. Giese, 2000: A simple ocean data assimilation analysis of the global upper ocean, 1950–95. Part I: Methodology. J. Phys. Oceanogr, 30 , 294309.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Ji, and H. Li, 1997: A decadal climate variation in the tropical Atlantic Ocean from thermodynamics and air–sea interactions. Nature, 385 , 516518.

    • Search Google Scholar
    • Export Citation
  • Chang, P., R. Saravanan, L. Ji, and G. C. Hegerl, 2000: The effect of local sea surface temperatures on the atmospheric circulation over the tropical Atlantic sector. J. Climate, 13 , 21952216.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Ji, and R. Saravanan, 2001: A hybrid coupled model study of tropical Atlantic variability. J. Climate, 14 , 361390.

  • Clarke, A. J., and A. Lebedev, 1997: Interannual and decadal changes in equatorial wind stress in the Atlantic, Indian, and Pacific Oceans and the Eastern Ocean Coastal Response. J. Climate, 10 , 17221729.

    • Search Google Scholar
    • Export Citation
  • Conkright, M. E., and Coauthors, 1998: Temperature. Vol. 5, World Ocean Database 1998, CD-ROM Scientific Dataset, Version 1.0, National Oceanographic Data Center Internal Rep. 14.

    • Search Google Scholar
    • Export Citation
  • Czaja, A., P. van der Vaart, and J. Marshall, 2002: A diagnostic study of the role of remote forcing in tropical Atlantic variability. J. Climate, 15 , 32803290.

    • Search Google Scholar
    • Export Citation
  • Dommenget, D., and M. Latif, 2000: Interannual to decadal variability in the tropical Atlantic. J. Climate, 13 , 777792.

  • Doney, S. C., S. Yeager, G. Danabasoglu, W. G. Large, and J. C. McWilliams, 2003: Modeling global oceanic interannual variability (1958–1997): Simulation design and model-data evaluation. NCAR Tech. Rep. NCAR/TN-452+STR, 48 pp.

    • Search Google Scholar
    • Export Citation
  • Enfield, D. B., and D. A. Mayer, 1997: Tropical Atlantic SST variability and its relation to El Niño–Southern Oscillation. J. Geophys. Res, 102 , 929945.

    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., 1999: A cautionary note on the use of statistical atmospheric models in the middle latitudes: Comments on “Decadal variability in the North Pacific as simulated by a hybrid coupled model.”. J. Climate, 12 , 18711872.

    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., and K. Hasselmann, 1977: Stochastic climate models. Part II: Application to sea-surface temperature anomalies and thermocline variability. Tellus, 29 , 284305.

    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., and E. Kestenare, 2002: The surface heat flux feedback. Part 1: Estimates from observations in the Atlantic and the North Pacific. Climate Dyn, 19 , 633647.

    • Search Google Scholar
    • Export Citation
  • Frankignoul, C., E. Kestenare, M. Botzet, A. F. Carril, H. Drange, A. Pardens, L. Terray, and R. Sutton, 2004: An intercomparison between the surface heat flux feedback in five coupled models, COADS, and the NCEP reanalysis. Climate Dyn, 22 , 373388.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr, 20 , 150155.

  • Gent, P. R., J. Willebrand, T. J. McDougall, and J. C. McWilliams, 1995: Parameterizing eddy-induced tracer transports in ocean circulation models. J. Phys. Oceanogr, 25 , 463474.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., F. O. Bryan, G. Danabasoglu, S. C. Doney, W. R. Holland, W. G. Large, and J. C. McWilliams, 1998: The NCAR Climate System Model global ocean component. J. Climate, 11 , 12871306.

    • Search Google Scholar
    • Export Citation
  • Hanawa, K., P. Rual, R. Bailey, A. Sy, and M. Szabados, 1995: A new depth-time equation for Sippiocan TSK T-7, T-6, and T-4 expendable bathythermographs (XBT). Deep-Sea Res, A8 , 14231451.

    • Search Google Scholar
    • Export Citation
  • Hastenrath, S., 1990: Decadal-scale changes of the circulation in the tropical Atlantic sector associated with Sahel drought. Int. J. Climatol, 10 , 459472.

    • Search Google Scholar
    • Export Citation
  • Hellerman, S., and M. Rosenstein, 1983: Normal monthly wind stress over the World Ocean with error estimates. J. Phys. Oceanogr, 13 , 10931104.

    • Search Google Scholar
    • Export Citation
  • Houghton, R. W., 1991: The relationship of sea surface temperature to thermocline depth at annual and interannual time scales in the tropical Atlantic Ocean. J. Geophys. Res, 96 , 1517315185.

    • Search Google Scholar
    • Export Citation
  • Houghton, R. W., and Y. Tourre, 1992: Characteristics of low-frequency sea surface temperature fluctuations in the tropical Atlantic. J. Climate, 5 , 765771.

    • Search Google Scholar
    • Export Citation
  • Joyce, T. M., 1988: On the wind-driven cross-equatorial flow in the Atlantic Ocean. J. Phys. Oceanogr, 18 , 793799.

  • Joyce, T. M., C. Deser, and M. A. Spall, 2000: The relation between decadal variability of subtropical mode water and the North Atlantic Oscillation. J. Climate, 13 , 25502569.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc, 77 , 437471.

  • Katz, E. J., 1993: An interannual study of the Atlantic North Equatorial Countercurrent. J. Phys. Oceanogr, 23 , 116123.

  • Kushnir, Y., R. Seager, and J. Miller, 2002: A simple coupled model of tropical Atlantic decadal climate variability. Geophys. Res. Lett, 29 .2133, doi:10.1029/2002GL015874.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., and P. R. Gent, 1999: Validation of vertical mixing in an equatorial ocean model using large eddy simulations and observations. J. Phys. Oceanogr, 29 , 449464.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., G. Danabasoglu, and S. Doney, 1997: Sensitivity to surface forcing and boundary layer mixing in a global ocean model: Annual-mean climatology. J. Phys. Oceanogr, 27 , 24182447.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., G. Danabasoglu, J. C. McWilliams, P. R. Gent, and F. O. Bryan, 2001: Equatorial circulation of a global ocean climate model with anisotropic horizontal viscosity. J. Phys. Oceanogr, 31 , 518536.

    • Search Google Scholar
    • Export Citation
  • Mehta, V. M., 1998: Variability of the tropical ocean surface temperatures at decadal-multidecadal timescales. Part I: The Atlantic Ocean. J. Climate, 11 , 23512375.

    • Search Google Scholar
    • Export Citation
  • Mélice, J-L., and J. Servain, 2003: The tropical Atlantic meridional SST gradient index and its relationships with the SOI, NAO, and Southern Ocean. Climate Dyn, 20 , 447464.

    • Search Google Scholar
    • Export Citation
  • Merle, J., and S. Arnault, 1985: Seasonal variability of the surface dynamic topography in the tropical Atlantic Ocean. J. Mar. Res, 43 , 267288.

    • Search Google Scholar
    • Export Citation
  • Moura, D. W., and J. Shukla, 1981: On the dynamics of droughts in northeast Brazil: Observations, theory and numerical experiments with a general circulation model. J. Atmos. Sci, 38 , 26532675.

    • Search Google Scholar
    • Export Citation
  • Nobre, P., and J. Shukla, 1996: Variations of sea surface temperature, wind stress, and rainfall over the tropical Atlantic and South America. J. Climate, 9 , 24642479.

    • Search Google Scholar
    • Export Citation
  • Philander, S. G., 1989: El Niño, La Niña, and the Southern Oscillation. Academic Press, 293 pp.

  • Qiu, B., and T. M. Joyce, 1992: Interannual variability in the mid- and low-latitude western North Pacific. J. Phys. Oceanogr, 22 , 10621079.

    • Search Google Scholar
    • Export Citation
  • Reynolds, R. W., and T. M. Smith, 1994: Improved global sea surface temperature analysis using optimum interpolation. J. Climate, 7 , 929948.

    • Search Google Scholar
    • Export Citation
  • Ruiz-Barradas, A., J. A. Carton, and S. Nigam, 2000: Structure of interannual-to-decadal climate variability in the tropical Atlantic sector. J. Climate, 13 , 32853297.

    • Search Google Scholar
    • Export Citation
  • Seager, R., Y. Kushnir, P. Chang, N. Naik, J. Miller, and W. Hazeleger, 2001: Looking for the role of the ocean in tropical Atlantic decadal climate variability. J. Climate, 14 , 638655.

    • Search Google Scholar
    • Export Citation
  • Servain, J., 1991: Simple climatic indices for the tropical Atlantic Ocean and some applications. J. Geophys. Res, 96 , 1513715146.

  • Servain, J., G. Clauzet, and I. C. Wainer, 2003: Modes of tropical Atlantic climate variability observed by PIRATA. Geophys. Res. Lett.,30, 8003, doi:10, 1029/22002GL015124.

    • Search Google Scholar
    • Export Citation
  • Smith, S. R., D. M. Legler, and K. V. Verzone, 2001: Quantifying uncertaintities in NCEP reanalysis using high-quality research vessel observations. J. Climate, 14 , 40624072.

    • Search Google Scholar
    • Export Citation
  • Sutton, R. T., S. P. Jewson, and D. P. Rowell, 2000: The elements of climate variability in the tropical Atlantic region. J. Climate, 13 , 32613284.

    • Search Google Scholar
    • Export Citation
  • White, W. B., 1995: Design of a global observing system for the gyre-scale upper ocean temperature variability. Progress in Oceanography, Vol. 36, Pergamon, 169–217.

    • Search Google Scholar
    • Export Citation
  • Xie, S-P., 1999: A dynamic ocean–atmosphere model of the tropical Atlantic decadal variability. J. Climate, 12 , 6470.

  • Yang, J., 1999: A linkage for decadal climate variations in Labrador Sea and the tropical Atlantic Ocean. Geophys. Res. Lett, 26 , 10231026.

    • Search Google Scholar
    • Export Citation
  • Zhou, Z., and J. Carton, 1998: Latent heat flux and interannual variability of the coupled atmosphere–ocean system. J. Atmos. Sci, 55 , 494501.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 123 33 0
PDF Downloads 45 16 1