• Bindoff, N. L., , and T. J. McDougall, 1994: Diagnosing climate change and ocean ventilation using hydrographic data. J. Phys. Oceanogr, 24 , 11371152.

    • Search Google Scholar
    • Export Citation
  • Church, J. A., , J. S. Godfrey, , D. R. Jackett, , and T. J. McDougal, 1991: A model of sea level rise caused by ocean thermal expansion. J. Climate, 4 , 438456.

    • Search Google Scholar
    • Export Citation
  • Fedorov, A. V., , and S. G. Philander, 2001: A stability analysis of tropical ocean–atmosphere interactions: Bridging measurements and theory for El Niño. J. Climate, 14 , 30863101.

    • Search Google Scholar
    • Export Citation
  • Frey, H., , M. Latif, , and T. Stockdale, 1997: The coupled model ECHO- 2. Part I: The tropical Pacific. Mon. Wea. Rev, 125 , 703720.

  • Giese, B. S., , S. C. Urizar, , and N. S. Fuckar, 2002: Southern Hemisphere origins of the 1976 climate shift. Geophys. Res. Lett.,29, 1014, doi:10.1029/2001GL013268.

    • Search Google Scholar
    • Export Citation
  • Gordon, A. L., 1986: Interocean exchange of thermocline water. J. Geophys. Res, 91C , 50375050.

  • Gu, D. F., , and S. G. H. Philander, 1997: Interdecadal climate fluctuations that depend on exchanges between the Tropics and extratropics. Science, 275 , 805807.

    • Search Google Scholar
    • Export Citation
  • Hall, A., , and S. Manabe, 1997: Can local linear stochastic theory explain sea surface temperature and salinity variability? Climate Dyn, 13 , 167180.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., , and M. J. McPhaden, 1999: Interior pycnocline flow from the subtropical to the equatorial Pacific Ocean. J. Phys. Oceanogr, 29 , 30733089.

    • Search Google Scholar
    • Export Citation
  • Kessler, W. S., 1999: Interannual variability of the subsurface high salinity tongue south of the equator at 165°E. J. Phys. Oceanogr, . 29 , 20382049.

    • Search Google Scholar
    • Export Citation
  • Kleeman, R., , J. P. McCreary, , and B. A. Klinger, 1999: A mechanism for generating ENSO decadal variability. Geophys. Res. Lett, . 26 , 17431746.

    • Search Google Scholar
    • Export Citation
  • Latif, M., , and T. P. Barnett, 1994: Causes of decadal climate variability over the North Pacific and North America. Science, 266 , 634637.

    • Search Google Scholar
    • Export Citation
  • Lukas, R., 2001: Freshening of the upper thermocline in the North Pacific subtropical gyre associated with decadal changes of rainfall. Geophys. Res. Lett, 28 , 34853488.

    • Search Google Scholar
    • Export Citation
  • Lukas, R., , and E. Lindstrom, 1991: The mixed layer of the western equatorial Pacific. J. Geophys. Res, 96 , (Suppl.),. 33433357.

  • McCreary, J. P., , and P. Lu, 1994: Interaction between the subtropical and equatorial ocean circulation—The subtropical cell. J. Phys. Oceanogr, 24 , 466497.

    • Search Google Scholar
    • Export Citation
  • Miller, A. J., , D. R. Cayan, , and W. B. White, 1998: A westward intensified decadal change in the North Pacific thermocline and gyre-scale circulation. J. Climate, 11 , 31123127.

    • Search Google Scholar
    • Export Citation
  • Munk, W., 1981: Internal waves and small scale processes. Evolution of Physical Oceanography, B. A. Warren and C. Wunsch, Eds., MIT Press, 264–291.

    • Search Google Scholar
    • Export Citation
  • Pierce, D. W., , T. P. Barnett, , and M. Latif, 2000: Connections between the Pacific Ocean Tropics and midlatitudes on decadal time scales. J. Climate, 13 , 11731194.

    • Search Google Scholar
    • Export Citation
  • Roeckner, E., and Coauthors, 1996: The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate. Max-Planck-Institute for Meteorology Tech. Rep. 218, 99 pp. [Available from DKRZ, Bundesstr. 55, 20146 Hamburg, Germany.].

    • Search Google Scholar
    • Export Citation
  • Schneider, N., 2000: A decadal spiciness mode in the Tropics. Geophys. Res. Lett, 27 , 257260.

  • Schneider, N., , A. J. Miller, , and D. W. Pierce, 2002: Anatomy of North Pacific decadal variability. J. Climate, 15 , 586605.

  • Seager, R., , S. E. Zebiak, , and M. A. Cane, 1988: A model of the tropical Pacific sea surface temperature climatology. J. Geophys. Res, 93 , 12651280.

    • Search Google Scholar
    • Export Citation
  • Seager, R., , Y. Kushnir, , N. Naik, , M. A. Cane, , and J. A. Miller, 2001: Wind- driven shifts of the Kuroshio–Oyanshio Extension and the generation of SST anomalies on decadal time scales. J. Climate, 14 , 42494265.

    • Search Google Scholar
    • Export Citation
  • Suga, T., , A. Kato, , and K. Hanawa, 2000: North Pacific tropical water: Its climatology and temporal changes associated with the climate regime shift in the 1970s. Progress in Oceanography, Vol. 47. Pergamon, 223–256.

    • Search Google Scholar
    • Export Citation
  • Yeager, S. G., , and W. G. Large, 2004: Late winter generation of spiciness on subducted isopycnals. J. Phys. Oceanogr., in press.

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The Response of Tropical Climate to the Equatorial Emergence of Spiciness Anomalies

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  • 1 International Pacific Research Center, and Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii
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Abstract

The ocean–atmosphere response to the surfacing of temperature anomalies from the oceanic thermocline is a key process in climate variability with decadal time scales. Using a coupled general circulation model, it is shown how density-compensating temperature and salinity (spiciness) anomalies emerging in the upwelling region of the equatorial Pacific modulate tropical climate.

Upon reaching the surface in the central equatorial Pacific, warm and salty spiciness anomalies increase sea surface temperature and salinity, and vent their heat anomaly to the atmosphere, primarily by the latent heat flux. The associated surface buoyancy flux increases vertical mixing, and thereby dampens surface temperature anomalies. The moisture added to the atmosphere increases precipitation in the western Pacific and intertropical convergence zone, and strengthens the trade winds east, and weakens them west of the date line. Central equatorial Pacific surface temperatures are slightly warmed by the resulting deepened thermocline, and additional warm spiciness anomalies due to a northward displacement of the climatological spiciness front on the equator, recycling salt anomalies in the shallow equatorial circulation and subduction from the Southern Hemisphere. From the Northern Hemisphere source regions of equatorial thermocline waters, cool and fresh anomalies result from the increased air–sea freshwater fluxes and wind-driven changes of the flow paths in the thermocline. The amplitudes of the model's El Niño–La Niña are diminished by warm spiciness anomalies due to a reduction of the temperature gradient in density coordinates that controls the thermocline feedback.

The coupled response is qualitatively consistent with a coupled climate mode that results from a positive feedback between the equatorial emergence of spiciness anomalies and the equatorial pycnocline and Southern Hemisphere responses, and a delayed, negative feedback due to Northern Hemisphere subduction. However, feedbacks are weak, and, at best, slightly enhance a decadal modulation of the Tropics due to spiciness anomalies generated by stochastic atmospheric forcing.

Corresponding author address: Dr. Niklas Schneider, International Pacific Research Center, University of Hawaii at Manoa, 1680 East West Road, Honolulu, HI 96822. Email: nschneid@hawaii.edu

Abstract

The ocean–atmosphere response to the surfacing of temperature anomalies from the oceanic thermocline is a key process in climate variability with decadal time scales. Using a coupled general circulation model, it is shown how density-compensating temperature and salinity (spiciness) anomalies emerging in the upwelling region of the equatorial Pacific modulate tropical climate.

Upon reaching the surface in the central equatorial Pacific, warm and salty spiciness anomalies increase sea surface temperature and salinity, and vent their heat anomaly to the atmosphere, primarily by the latent heat flux. The associated surface buoyancy flux increases vertical mixing, and thereby dampens surface temperature anomalies. The moisture added to the atmosphere increases precipitation in the western Pacific and intertropical convergence zone, and strengthens the trade winds east, and weakens them west of the date line. Central equatorial Pacific surface temperatures are slightly warmed by the resulting deepened thermocline, and additional warm spiciness anomalies due to a northward displacement of the climatological spiciness front on the equator, recycling salt anomalies in the shallow equatorial circulation and subduction from the Southern Hemisphere. From the Northern Hemisphere source regions of equatorial thermocline waters, cool and fresh anomalies result from the increased air–sea freshwater fluxes and wind-driven changes of the flow paths in the thermocline. The amplitudes of the model's El Niño–La Niña are diminished by warm spiciness anomalies due to a reduction of the temperature gradient in density coordinates that controls the thermocline feedback.

The coupled response is qualitatively consistent with a coupled climate mode that results from a positive feedback between the equatorial emergence of spiciness anomalies and the equatorial pycnocline and Southern Hemisphere responses, and a delayed, negative feedback due to Northern Hemisphere subduction. However, feedbacks are weak, and, at best, slightly enhance a decadal modulation of the Tropics due to spiciness anomalies generated by stochastic atmospheric forcing.

Corresponding author address: Dr. Niklas Schneider, International Pacific Research Center, University of Hawaii at Manoa, 1680 East West Road, Honolulu, HI 96822. Email: nschneid@hawaii.edu

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