• Balmaseda, M. A., , A. Vidard, , and D. L. T. Anderson, 2008: The ECMWF ocean analysis system: ORA-S3. Mon. Wea. Rev., 136, 30183034, doi:10.1175/2008MWR2433.1.

    • Search Google Scholar
    • Export Citation
  • Bosc, C., , and T. Delcroix, 2008: Observed equatorial Rossby waves and ENSO-related warm water volume changes in the equatorial Pacific Ocean. J. Geophys. Res., 113, C06003, doi:10.1029/2007JC004613.

    • Search Google Scholar
    • Export Citation
  • Brown, J., , and A. V. Fedorov, 2010: Estimating the diapycnal transport contribution to warm water volume variations in the tropical Pacific Ocean. J. Climate, 23, 221237, doi:10.1175/2009JCLI2347.1.

    • Search Google Scholar
    • Export Citation
  • Bunge, L., , and A. J. Clarke, 2009: A verified estimation of the El Niño index Niño-3.4 since 1877. J. Climate, 22, 39793992, doi:10.1175/2009JCLI2724.1.

    • Search Google Scholar
    • Export Citation
  • Cane, M. A., , and S. E. Zebiak, 1985: A theory for El Niño and Southern Oscillation. Science, 228, 10851087, doi:10.1126/science.228.4703.1085.

    • Search Google Scholar
    • Export Citation
  • Carton, J. A., , and B. S. Giese, 2008: A reanalysis of ocean climate using Simple Ocean Data Assimilation (SODA). Mon. Wea. Rev., 136, 29993017, doi:10.1175/2007MWR1978.1.

    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., 1983: The reflection of equatorial waves from oceanic boundaries. J. Phys. Oceanogr., 13, 11931207, doi:10.1175/1520-0485(1983)013<1193:TROEWF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., 2008: An Introduction to the Dynamics of El Niño and the Southern Oscillation. Academic Press, 324 pp.

  • Clarke, A. J., 2010: Analytical theory for the quasi-steady and low-frequency equatorial ocean response to wind forcing: The “tilt” and “warm water volume” modes. J. Phys. Oceanogr., 40, 121137, doi:10.1175/2009JPO4263.1.

    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., , and A. Lebedev, 1996: Long-term changes in the equatorial Pacific trade winds. J. Climate, 9, 10201029, doi:10.1175/1520-0442(1996)009<1020:LTCITE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., , and S. Van Gorder, 2003: Improving El Niño prediction using a space–time integration of Indo-Pacific winds and equatorial Pacific upper ocean heat content. Geophys. Res. Lett., 30, 1399, doi:10.1029/2002GL016673.

    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., , S. Van Gorder, , and G. Colantuono, 2007: Wind stress curl and ENSO discharge/recharge in the equatorial Pacific. J. Phys. Oceanogr., 37, 10771091, doi:10.1175/JPO3035.1.

    • Search Google Scholar
    • Export Citation
  • Ebisuzaki, W., 1997: A method to estimate the statistical significance of a correlation when the data are serially correlated. J. Climate, 10, 21472153, doi:10.1175/1520-0442(1997)010<2147:AMTETS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Fedorov, A. V., 2010: Ocean response to wind variations, warm water volume, and simple models of ENSO in the low-frequency approximation. J. Climate, 23, 38553873, doi:10.1175/2010JCLI3044.1.

    • Search Google Scholar
    • Export Citation
  • Gill, A. E., , and A. J. Clarke, 1974: Wind-induced upwelling, coastal currents and sea-level changes. Deep-Sea Res. Oceanogr. Abstr., 21, 325345, doi:10.1016/0011-7471(74)90038-2.

    • Search Google Scholar
    • Export Citation
  • Horii, T., , I. Ueki, , and K. Hanawa, 2012: Breakdown of ENSO predictors in the 2000s: Decadal changes of recharge/discharge–SST phase relation and atmospheric intraseasonal forcing. Geophys. Res. Lett., 39, L10707, doi:10.1029/2012GL051740.

    • Search Google Scholar
    • Export Citation
  • Ji, M., , and A. Leetmaa, 1997: Impact of data assimilation on ocean initialization and El Niño prediction. Mon. Wea. Rev., 125, 742753, doi:10.1175/1520-0493(1997)125<0742:IODAOO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Jin, F.-F., 1997: An equatorial ocean recharge paradigm for ENSO. Part I: Conceptual model. J. Atmos. Sci., 54, 811829, doi:10.1175/1520-0469(1997)054<0811:AEORPF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kessler, W. S., 1990: Observations of long Rossby waves in the northern tropical Pacific. J. Geophys. Res., 95 (C4), 51835217, doi:10.1029/JC095iC04p05183.

    • Search Google Scholar
    • Export Citation
  • Kessler, W. S., 2002: Is ENSO a cycle or a series of events? Geophys. Res. Lett.,29, 2125, doi:10.1029/2002GL015924.

  • Liebmann, B., , and C. A. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77, 12751277.

    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., 2003: Tropical Pacific Ocean heat content variations and ENSO persistence barriers. Geophys. Res. Lett., 30, 1480, doi:10.1029/2003GL016872.

    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., 2012: A 21st century shift in the relationship between ENSO SST and warm water volume anomalies. Geophys. Res. Lett., 39, L09706, doi:10.1029/2012GL051826.

    • Search Google Scholar
    • Export Citation
  • Meinen, C. S., , and M. J. McPhaden, 2000: Observations of warm water volume changes in the equatorial Pacific and their relationship to El Niño and La Niña. J. Climate, 13, 35513559, doi:10.1175/1520-0442(2000)013<3551:OOWWVC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Meinen, C. S., , and M. J. McPhaden, 2001: Interannual variability in warm water volume transports in the equatorial Pacific during 1993–99. J. Phys. Oceanogr., 31, 13241345, doi:10.1175/1520-0485(2001)031<1324:IVIWWV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Rajeevan, M., , and M. J. McPhaden, 2004: Tropical Pacific upper ocean heat content variations and Indian summer monsoon rainfall. Geophys. Res. Lett., 31, L18203, doi:10.1029/2004GL020631.

    • Search Google Scholar
    • Export Citation
  • Shu, L., , and A. J. Clarke, 2002: Using an ocean model to examine ENSO dynamics. J. Phys. Oceanogr., 32, 903923, doi:10.1175/1520-0485(2002)032<0903:UAOMTE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Smith, N. R., 1995a: An improved system for tropical ocean subsurface temperature analysis. J. Atmos. Oceanic Technol., 12, 850870, doi:10.1175/1520-0426(1995)012<0850:AISFTO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Smith, N. R., 1995b: The BMRC ocean thermal analysis system. Aust. Meteor. Mag., 44, 93110.

  • Tang, Y., , and Z. Deng, 2010: Tropical Pacific upper ocean heat content variations and ENSO predictability during the period from 1881–2000. Adv. Geosci., 18, 87108.

    • Search Google Scholar
    • Export Citation
  • Torrence, C., , and G. P. Compo, 1998: A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 79, 6178, doi:10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1984: Signal versus noise in the Southern Oscillation. Mon. Wea. Rev., 112, 326332, doi:10.1175/1520-0493(1984)112<0326:SVNITS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Yeh, S.-W., , J.-S. Kug, , B. Dewitte, , M.-H. Kwon, , B. P. Kirtman, , and F.-F. Jin, 2009: El Niño in a changing climate. Nature, 461, 511514, doi:10.1038/nature08316.

    • Search Google Scholar
    • Export Citation
  • Zebiak, S. E., 1989: Oceanic heat content variability and El Niño cycles. J. Phys. Oceanogr., 19, 475486, doi:10.1175/1520-0485(1989)019<0475:OHCVAE>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Zebiak, S. E., , and M. A. Cane, 1987: A model El Niño–Southern Oscillation. Mon. Wea. Rev., 115, 22622278, doi:10.1175/1520-0493(1987)115<2262:AMENO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
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On the Warm Water Volume and Its Changing Relationship with ENSO

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  • 1 Department of Earth, Ocean and Atmospheric Science, The Florida State University, Tallahassee, Florida
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Abstract

The interannual, equatorial Pacific, 20°C isotherm depth variability since 1980 is dominated by two empirical orthogonal function (EOF) modes: the “tilt” mode, having opposite signs in the eastern and western equatorial Pacific and in phase with zonal wind forcing and El Niño–Southern Oscillation (ENSO) indices, and a second EOF mode of one sign across the Pacific. Because the tilt mode is of opposite sign in the eastern and western equatorial Pacific while the second EOF mode is of one sign, the second mode has been associated with the warm water volume (WWV), defined as the volume of water above the 20°C isotherm from 5°S to 5°N, 120°E to 80°W. Past work suggested that the WWV led the tilt mode by about 2–3 seasons, making it an ENSO predictor. But after 1998 the lead has decreased and WWV-based predictions of ENSO have failed. The authors constructed a sea level–based WWV proxy back to 1955, and before 1973 it also exhibited a smaller lead. Analysis of data since 1980 showed that the decreased WWV lead is related to a marked increase in the tilt mode contribution to the WWV and a marked decrease in second-mode EOF amplitude and its contribution. Both pre-1973 and post-1998 periods of reduced lead were characterized by “mean” La Niña–like conditions, including a westward displacement of the anomalous wind forcing. According to recent theory, and consistent with observations, such westward displacement increases the tilt mode contribution to the WWV and decreases the second-mode amplitude and its WWV contribution.

Corresponding author address: Lucia Bunge, Department of Earth, Ocean and Atmospheric Science, The Florida State University, P.O. Box 3064520, Tallahassee, FL 32306-4520. E-mail: lbunge@fsu.edu

Abstract

The interannual, equatorial Pacific, 20°C isotherm depth variability since 1980 is dominated by two empirical orthogonal function (EOF) modes: the “tilt” mode, having opposite signs in the eastern and western equatorial Pacific and in phase with zonal wind forcing and El Niño–Southern Oscillation (ENSO) indices, and a second EOF mode of one sign across the Pacific. Because the tilt mode is of opposite sign in the eastern and western equatorial Pacific while the second EOF mode is of one sign, the second mode has been associated with the warm water volume (WWV), defined as the volume of water above the 20°C isotherm from 5°S to 5°N, 120°E to 80°W. Past work suggested that the WWV led the tilt mode by about 2–3 seasons, making it an ENSO predictor. But after 1998 the lead has decreased and WWV-based predictions of ENSO have failed. The authors constructed a sea level–based WWV proxy back to 1955, and before 1973 it also exhibited a smaller lead. Analysis of data since 1980 showed that the decreased WWV lead is related to a marked increase in the tilt mode contribution to the WWV and a marked decrease in second-mode EOF amplitude and its contribution. Both pre-1973 and post-1998 periods of reduced lead were characterized by “mean” La Niña–like conditions, including a westward displacement of the anomalous wind forcing. According to recent theory, and consistent with observations, such westward displacement increases the tilt mode contribution to the WWV and decreases the second-mode amplitude and its WWV contribution.

Corresponding author address: Lucia Bunge, Department of Earth, Ocean and Atmospheric Science, The Florida State University, P.O. Box 3064520, Tallahassee, FL 32306-4520. E-mail: lbunge@fsu.edu
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