Editorial Type:
Article
Article Type:
Research Article

The Southern Ocean as a Source Region for Tropical Atlantic Variability

Hannah Hickey School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada

Search for other papers by Hannah Hickey in
Current site
Google Scholar
PubMed Close
and
Andrew J. Weaver School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada

Search for other papers by Andrew J. Weaver in
Current site
Google Scholar
PubMed Close
Print Publication:
15 Oct 2004
DOI:
https://doi.org/10.1175/1520-0442(2004)017<3960:TSOAAS>2.0.CO;2
Page(s):
3960–3972
Restricted access

We are aware of a technical issue preventing figures and tables from showing in some newly published articles in the full-text HTML view.
While we are resolving the problem, please use the online PDF version of these articles to view figures and tables.

Abstract

A coupled model of intermediate complexity is used to examine the effect of the Southern Ocean on tropical Atlantic variability. Model experiments with positive surface temperature, freshwater, and wind forcings in the Southern Ocean show an increased advection of polar water into the Atlantic basin, resulting in anomalously cold freshwater in the eastern Atlantic Ocean at 25°S. With time, these anomalies spread northward and away from the coast, into the tropical thermocline. The magnitude of the response increases linearly with the strength of the forcing. The results of these experiments show that southeastern Atlantic Ocean temperature and salinity are particularly sensitive to changes in the Southern Ocean. These findings suggest that this link could be the oceanic branch of a mode of variability linking the Southern and tropical Atlantic Oceans—a possible mechanism for the as-yet-unexplained decadal mode of tropical Atlantic variability.

Corresponding author address: Dr. Andrew J. Weaver, School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055 STN CSC, Victoria, BC V8W 3P6, Canada. Email: weaver@uvic.ca

Abstract

A coupled model of intermediate complexity is used to examine the effect of the Southern Ocean on tropical Atlantic variability. Model experiments with positive surface temperature, freshwater, and wind forcings in the Southern Ocean show an increased advection of polar water into the Atlantic basin, resulting in anomalously cold freshwater in the eastern Atlantic Ocean at 25°S. With time, these anomalies spread northward and away from the coast, into the tropical thermocline. The magnitude of the response increases linearly with the strength of the forcing. The results of these experiments show that southeastern Atlantic Ocean temperature and salinity are particularly sensitive to changes in the Southern Ocean. These findings suggest that this link could be the oceanic branch of a mode of variability linking the Southern and tropical Atlantic Oceans—a possible mechanism for the as-yet-unexplained decadal mode of tropical Atlantic variability.

Corresponding author address: Dr. Andrew J. Weaver, School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055 STN CSC, Victoria, BC V8W 3P6, Canada. Email: weaver@uvic.ca

Save
Cover Journal of Climate
Journal of Climate

  • Bitz, C., M. Holland, A. Weaver, and M. Eby, 2001: Simulating the ice-thickness distribution in a coupled climate model. J. Geophys. Res, 106 , 2441–2464.

    • Search Google Scholar
    • Export Citation

  • Boyer, T. P., and S. Levitus, 2002: Harmonic analysis of climatological sea surface salinity. J. Geophys. Res.,107, 8006, doi:10.1029/ 2001JC000829.

    • Search Google Scholar
    • Export Citation

  • Bryan, K., and L. Lewis, 1979: A water mass model of the world ocean. J. Geophys. Res, 84 , 2503–2517.

  • Cai, W., and P. H. Whetton, 2001: A time-varying greenhouse warming pattern and the tropical–extratropical circulation linkage in the Pacific Ocean. J. Climate, 14 , 3337–3355.

    • Search Google Scholar
    • Export Citation

  • Carril, A., and A. Navarra, 2001: Low-frequency variability of the Antarctic Circumpolar Wave. Geophys. Res. Lett, 28 , 4623–4626.

  • Carton, J., X. Cao, B. Giese, and A. da Silva, 1996: Decadal and interannual SST variability in the tropical Atlantic Ocean. J. Phys. Oceanogr, 26 , 1165–1175.

    • Search Google Scholar
    • Export Citation

  • Chang, P., L. Ji, and H. Li, 1997: A decadal climate variation in the tropical Atlantic Ocean from thermodynamic air–sea interactions. Nature, 385 , 516–518.

    • Search Google Scholar
    • Export Citation

  • Chang, P., R. Saravanan, L. Ji, and G. Hegerl, 2000: The effect of local sea surface temperatures on atmospheric circulation over the tropical Atlantic sector. J. Climate, 13 , 2195–2216.

    • Search Google Scholar
    • Export Citation

  • Curry, R., M. McCartney, and T. Joyce, 1998: Oceanic transport of subpolar climate signals to mid-depth subtropical waters. Nature, 391 , 575–577.

    • Search Google Scholar
    • Export Citation

  • Dommenget, D., and M. Latif, 2000: Interannual to decadal variability in the tropical Atlantic. J. Climate, 13 , 777–792.

  • Enfield, D., and D. Mayer, 1997: Tropical Atlantic sea surface temperature variability and its relation to El Niño–Southern Oscillation. J. Geophys. Res, 102 , 929–945.

    • Search Google Scholar
    • Export Citation

  • England, M. H., J. S. Godfrey, A. C. Hirst, and M. Tomczak, 1993: The mechanism for Antarctic Intermediate Water renewal in a World Ocean model. J. Phys. Oceanogr, 23 , 1553–1560.

    • Search Google Scholar
    • Export Citation

  • Gent, P., and J. McWilliams, 1990: Isopycnal mixing in ocean general circulation models. J. Phys. Oceanogr, 20 , 150–155.

  • Gent, P., J. Willebrand, T. McDougall, and J. McWilliams, 1995: Parameterizing eddy-induced tracer transports in ocean circulation models. J. Phys. Oceanogr, 24 , 463–474.

    • Search Google Scholar
    • Export Citation

  • Gu, D., and G. Philander, 1997: Internal climate fluctuations that depend on exchanges between the tropics and extratropics. Science, 275 , 805–807.

    • Search Google Scholar
    • Export Citation

  • Häkkinen, S., and K. Mo, 2002: The low-frequency variability of the tropical Atlantic Ocean. J. Climate, 15 , 237–250.

  • Harper, S., 2000: Thermocline ventilation and pathways of tropical– subtropical water mass exchange. Tellus, 52 , 330–345.

  • Hastenrath, S., 1976: Variations in low-latitude circulation and extreme climatic events in the tropical Americas. J. Atmos. Sci, 33 , 202–215.

    • Search Google Scholar
    • Export Citation

  • Hastenrath, S., and L. Greischar, 1993: Further work on the prediction of northeast Brazil rainfall anomalies. J. Climate, 6 , 743–758.

    • Search Google Scholar
    • Export Citation

  • Hirst, A. C., S. P. O'Farrell, and H. B. Gordon, 2000: Comparison of a coupled ocean–atmosphere model with and without oceanic eddy-induced advection. Part I: Ocean spinup and control integrations. J. Climate, 13 , 139–163.

    • Search Google Scholar
    • Export Citation

  • Houghton, R., and Y. Tourre, 1992: Characteristics of low-frequency sea surface temperature fluctuations in the tropical Atlantic. J. Climate, 5 , 765–771.

    • Search Google Scholar
    • Export Citation

  • Huang, B., and J. Shukla, 1997: Characteristics of the interannual and decadal variability in a general circulation model of the tropical Atlantic Ocean. J. Phys. Oceanogr, 27 , 1693–1712.

    • Search Google Scholar
    • Export Citation

  • Hunke, E., and J. Dukowicz, 1997: An elastic–viscous–plastic model for sea ice dynamics. J. Phys. Oceanogr, 27 , 1849–1867.

  • Jacobs, S. S., and J. C. Comiso, 1997: Climate variability in the Amundsen and Bellingshausen Seas. J. Climate, 10 , 697–709.

  • Jochum, M., and P. Malanotte-Rizzoli, 2001: Influence of the meridional overturning circulation on tropical–subtropical pathways. J. Phys. Oceanogr, 31 , 1313–1323.

    • Search Google Scholar
    • Export Citation

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc, 77 , 437–471.

  • Kleeman, R., J. P. McCreary Jr., and B. A. Klinger, 1999: A mechanism for generating ENSO decadal variability. Geophys. Res. Lett, 26 , 1743–1746.

    • Search Google Scholar
    • Export Citation

  • Lamb, P., R. Peppler, and S. Hastenrath, 1986: Interannual variability in the tropical Atlantic. Nature, 322 , 238–239.

  • Lazar, A., R. Murtugudde, and A. Busalacchi, 2001: A model study of temperature anomaly propagation from the subtropics to tropics within the south Atlantic thermocline. Geophys. Res. Lett, 28 , 1271–1274.

    • Search Google Scholar
    • Export Citation

  • McCartney, M., 1977: Subantarctic mode water. A Voyage of Discovery: George Deacon 70th Anniversary Volume, M. Angel, Ed., Pergamon Press, 103–119.

    • Search Google Scholar
    • Export Citation

  • McPhaden, M., and D. Zhang, 2002: Slowdown of the meridional overturning circulation in the upper Pacific Ocean. Nature, 415 , 603–608.

    • 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 , 2351–2375.

    • Search Google Scholar
    • Export Citation

  • Mehta, V. M., and T. Delworth, 1995: Decadal variability of the tropical ocean surface temperature in shipboard measurements and in a global ocean–atmosphere model. J. Climate, 8 , 172–190.

    • 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 , 2464–2479.

    • Search Google Scholar
    • Export Citation

  • Okumura, Y., S. Xie, A. Numaguti, and Y. Tanimoto, 2001: Tropical Atlantic air–sea interaction and its influence on the NAO. Geophys. Res. Lett, 28 , 1507–1510.

    • Search Google Scholar
    • Export Citation

  • Rajagopalan, B., Y. Kushnir, and Y. Tourre, 1998: Observed decadal midlatitude and tropical Atlantic climate variability. Geophys. Res. Lett, 25 , 3967–3970.

    • Search Google Scholar
    • Export Citation

  • Rintoul, S., and M. England, 2002: Ekman transport dominates local air–sea fluxes in driving variability of subantarctic mode water. J. Phys. Oceanogr, 32 , 1308–1321.

    • Search Google Scholar
    • Export Citation

  • Robertson, A., C. Mechoso, and Y-J. Kim, 2000: The influence of Atlantic sea surface temperature anomalies on the North Atlantic oscillation. J. Climate, 13 , 122–138.

    • 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 , 3285–3297.

    • Search Google Scholar
    • Export Citation

  • Saenko, O. A., A. J. Weaver, and M. H. England, 2003: A region of enhanced northward Antarctic Intermediate Water transport in a coupled climate model. J. Phys. Oceanogr, 33 , 1528–1535.

    • 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 , 638–655.

    • Search Google Scholar
    • Export Citation

  • Servain, J., 1991: Simple climatic indices for the tropical Atlantic Ocean and some applications. J. Geophys. Res, 96 , 15137–15146.

  • Sutton, R., S. Jewson, and D. Rowell, 2000: The elements of climate variability in the tropical Atlantic region. J. Climate, 13 , 3261–3284.

    • Search Google Scholar
    • Export Citation

  • Venegas, S., L. Mysak, and D. Straub, 1996: Evidence for interannual and interdecadal climate variability in the South Atlantic. Geophys. Res. Lett, 23 , 2673–2676.

    • Search Google Scholar
    • Export Citation

  • Venegas, S., M. Drinkwater, and G. Shaffer, 2001: Coupled oscillations in the Antarctic sea ice and atmosphere in the South Pacific sector. Geophys. Res. Lett, 28 , 3301–3304.

    • Search Google Scholar
    • Export Citation

  • Weaver, A., 1999: Extratropical subduction and decadal modulation of El Niño. Geophys. Res. Lett, 26 , 743–746.

  • Weaver, A., and Coauthors, 2001: The UVic earth system climate model: Model description, climatology, and applications to past, present and future climates. Atmos.–Ocean, 39 , 361–428.

    • Search Google Scholar
    • Export Citation

  • White, W. B., and R. G. Peterson, 1996: An Antarctic circumpolar wave in surface pressure, wind, temperature and sea-ice extent. Nature, 380 , 699–702.

    • Search Google Scholar
    • Export Citation

  • Xie, S-P., and Y. Tanimoto, 1998: A pan-Atlantic decadal climate oscillation. Geophys. Res. Lett, 25 , 2185–2188.

  • Yang, J., 1999: A linkage between decadal climate variations in the Labrador Sea and the tropical Atlantic Ocean. Geophys. Res. Lett, 26 , 1023–1026.

    • Search Google Scholar
    • Export Citation

  • Zebiak, S. E., 1993: Air–sea interaction in the equatorial Atlantic region. J. Climate, 6 , 1567–1586.