• Bernie, D. J., S. J. Woolnough, J. M. Slingo, and E. Guilyardi, 2005: Modeling diurnal and intraseasonal variability of the ocean mixed layer. J. Climate, 18, 11901202, https://doi.org/10.1175/JCLI3319.1.

    • Crossref
    • 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, https://doi.org/10.1029/2007JC004613.

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Burgers, G., F.-F. Jin, and G. J. van Oldenborgh, 2005: The simplest ENSO recharge oscillator. Geophys. Res. Lett., 32, L13706, https://doi.org/10.1029/2005GL022951.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cheng, L., K. E. Trenberth, J. T. Fasullo, M. Mayer, M. Balmaseda, and J. Zhu, 2019: Evolution of ocean heat content related to ENSO. J. Climate, 32, 35293556, https://doi.org/10.1175/JCLI-D-18-0607.1.

    • Crossref
    • 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, https://doi.org/10.1175/JPO3035.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Colella, P., and P. R. Woodward, 1984: The piecewise parabolic method (PPM) for gas-dynamical simulations. J. Comput. Phys., 54, 174201, https://doi.org/10.1016/0021-9991(84)90143-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Collins, M., and et al. , 2010: The impact of global warming on the tropical Pacific Ocean and El Niño. Nat. Geosci., 3, 391397, https://doi.org/10.1038/ngeo868.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dee, D. P., and et al. , 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553597, https://doi.org/10.1002/qj.828.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., and et al. , 2012: Simulated climate and climate change in the GFDL CM2.5 high-resolution coupled climate model. J. Climate, 25, 27552781, https://doi.org/10.1175/JCLI-D-11-00316.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Diaz, H. F., M. P. Hoerling, and J. K. Eischeid, 2001: ENSO variability, teleconnections and climate change. Int. J. Climatol., 21, 18451862, https://doi.org/10.1002/joc.631.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fairall, C. W., E. F. Bradley, D. P. Rogers, J. B. Edson, and G. S. Young, 1996: Bulk parameterization of air–sea fluxes for Tropical Ocean–Global Atmosphere Coupled Ocean– Atmosphere Response Experiment. J. Geophys. Res., 101, 37473764, https://doi.org/10.1029/95JC03205.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Feng, M., N. Zhang, Q. Liu, and S. Wijffels, 2018: The Indonesian throughflow, its variability and centennial change. Geosci. Lett., 5, 3, https://doi.org/10.1186/s40562-018-0102-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fox-Kemper, B., R. Ferrari, and R. Hallberg, 2008: Parameterization of mixed layer eddies. Part I: Theory and diagnosis. J. Phys. Oceanogr., 38, 11451165, https://doi.org/10.1175/2007JPO3792.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20, 150155, https://doi.org/10.1175/1520-0485(1990)020<0150:IMIOCM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., H. Peters, J. C. Wesson, N. S. Oakey, and T. J. Shay, 1985: Intensive measurements of turbulence and shear in the Equatorial Undercurrent. Nature, 318, 140144, https://doi.org/10.1038/318140a0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Griffies, S. M., 2012: Elements of the Modular Ocean Model (MOM). GFDL Ocean Group Tech. Rep. 7, NOAA/GFDL, 645 pp., https://mom-ocean.github.io/assets/pdfs/MOM5_manual.pdf.

  • Groeskamp, S., S. M. Griffies, D. Iudicone, R. Marsh, A. G. Nurser, and J. D. Zika, 2019: The water mass transformation framework for ocean physics and biogeochemistry. Annu. Rev. Mar. Sci., 11, 271305, https://doi.org/10.1146/annurev-marine-010318-095421.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hallberg, R., 2013: Using a resolution function to regulate parameterizations of oceanic mesoscale eddy effects. Ocean Modell., 72, 92103, https://doi.org/10.1016/j.ocemod.2013.08.007.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hartmann, D. L., and et al. , 2013: Observations: Atmosphere and surface. Climate Change 2013: The Physical Science Basis, T. F. Stocker et al., Eds., Cambridge University Press, 159–254.

  • Holmes, R. M., and L. N. Thomas, 2015: The modulation of equatorial turbulence by tropical instability waves in a regional ocean model. J. Phys. Oceanogr., 45, 11551173, https://doi.org/10.1175/JPO-D-14-0209.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holmes, R. M., J. D. Zika, and M. H. England, 2019a: Diathermal heat transport in a global ocean model. J. Phys. Oceanogr., 49, 141161, https://doi.org/10.1175/JPO-D-18-0098.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holmes, R. M., J. D. Zika, R. Ferrari, A. F. Thompson, E. R. Newsom, and M. H. England, 2019b: Atlantic Ocean heat transport enabled by Indo-Pacific heat uptake and mixing. Geophys. Res. Lett., 46, 13 93913 949, https://doi.org/10.1029/2019GL085160.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Horel, J. D., 1982: On the annual cycle of the tropical Pacific atmosphere and ocean. Mon. Wea. Rev., 110, 18631878, https://doi.org/10.1175/1520-0493(1982)110<1863:OTACOT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Izumo, T., M. Lengaigne, J. Vialard, I. Suresh, and Y. Planton, 2018: On the physical interpretation of the lead relation between warm water volume and the El Niño southern oscillation. Climate Dyn., 52, 29232942, https://doi.org/10.1007/S00382-018-4313-1.

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jin, F.-F., 1997b: An equatorial ocean recharge paradigm for ENSO. Part II: A stripped-down coupled model. J. Atmos. Sci., 54, 830847, https://doi.org/10.1175/1520-0469(1997)054<0830:AEORPF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jochum, M., G. Danabasoglu, M. Holland, Y.-O. Kwon, and W. G. Large, 2008: Ocean viscosity and climate. J. Geophys. Res., 113, C06017, https://doi.org/10.1029/2007JC004515.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., and A. N. Birnbaum, 2017: As El Niño builds, Pacific warm pool expands, ocean gains more heat. Geophys. Res. Lett., 44, 438445, https://doi.org/10.1002/2016GL071767.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kara, A. B., A. J. Wallcraft, E. J. Metzger, H. E. Hurlburt, and C. W. Fairall, 2007: Wind stress drag coefficient over the global ocean. J. Climate, 20, 58565864, https://doi.org/10.1175/2007JCLI1825.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kiss, A. E., and et al. , 2020: ACCESS-OM2: A global ocean–sea ice model at three resolutions. Geosci. Model Dev., 13, 401442, https://doi.org/10.5194/gmd-13-401-2020.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Large, W. G., and A. G. Nurser, 2001: Ocean surface water mass transformation. Ocean Circulation and Climate, G. Siedler, J. Church, and J. Gould, Eds., International Geophysics Series, Vol. 77, Academic Press, 317–336, https://doi.org/10.1016/S0074-6142(01)80126-1.

    • Crossref
    • Export Citation
  • Large, W. G., and S. G. Yeager, 2004: Diurnal to decadal global forcing for ocean and sea-ice models: The data sets and flux climatologies. NCAR Tech. Note NCAR/TN-460+STR, 105 pp., https://doi.org/10.5065/D6KK98Q6.

    • Crossref
    • Export Citation
  • Large, W. G., J. C. McWilliams, and S. C. Doney, 1994: Oceanic vertical mixing: A review and a model with a non-local boundary layer parameterization. Rev. Geophys., 32, 363403, https://doi.org/10.1029/94RG01872.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lengaigne, M., U. Hausmann, G. Madec, C. Menkes, J. Vialard, and J.-M. Molines, 2012: Mechanisms controlling warm water volume interannual variations in the equatorial Pacific: Diabatic versus adiabatic processes. Climate Dyn., 38, 10311046, https://doi.org/10.1007/s00382-011-1051-z.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lien, R.-C., D. R. Caldwell, M. C. Gregg, and J. N. Moum, 1995: Turbulence variability at the equator in the central Pacific at the beginning of the 1991–1993 El Niño. J. Geophys. Res., 100, 68816898, https://doi.org/10.1029/94JC03312.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, C., A. Köhl, Z. Liu, F. Wang, and D. Stammer, 2016: Deep-reaching thermocline mixing in the equatorial Pacific cold tongue. Nat. Commun., 7, 11576, https://doi.org/10.1038/ncomms11576.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, W., and et al. , 2015: Extended Reconstructed Sea Surface Temperature version 4 (ERSST.v4): Part II. Parametric and structural uncertainty estimations. J. Climate, 28, 931951, https://doi.org/10.1175/JCLI-D-14-00007.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Locarnini, R. A., and et al. , 2013: Temperature. Vol. 1, World Ocean Atlas 2013, NOAA Atlas NESDIS 73, 40 pp., http://data.nodc.noaa.gov/woa/WOA13/DOC/woa13_vol1.pdf.

  • McGregor, S., A. Timmermann, N. Schneider, M. F. Stuecker, and M. H. England, 2012: The effect of the South Pacific convergence zone on the termination of El Niño events and the meridional asymmetry of ENSO. J. Climate, 25, 55665586, https://doi.org/10.1175/JCLI-D-11-00332.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McGregor, S., N. Ramesh, P. Spence, M. H. England, M. J. McPhaden, and A. Santoso, 2013: Meridional movement of wind anomalies during ENSO events and their role in event termination. Geophys. Res. Lett., 40, 749754, https://doi.org/10.1002/grl.50136.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McGregor, S., P. Spence, F. U. Schwarzkopf, M. H. England, A. Santoso, W. S. Kessler, A. Timmermann, and C. W. Böning, 2014: ENSO-driven interhemispheric Pacific mass transports. J. Geophys. Res. Oceans, 119, 62216237, https://doi.org/10.1002/2014JC010286.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McGregor, S., A. Timmermann, F.-F. Jin, and W. S. Kessler, 2016: Charging El Niño with off-equatorial westerly wind events. Climate Dyn., 47, 11111125, https://doi.org/10.1007/s00382-015-2891-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McGregor, S., A. Sen Gupta, D. Dommenget, T. Lee, M. J. McPhaden, and W. S. Kessler, 2017: Factors influencing the skill of synthesized satellite wind products in the tropical Pacific. J. Geophys. Res. Oceans, 122, 10721089, https://doi.org/10.1002/2016JC012340.

    • Crossref
    • 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, https://doi.org/10.1029/2012GL051826.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., J. M. Arblaster, J. T. Fasullo, A. Hu, and K. E. Trenberth, 2011: Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods. Nat. Climate Change, 1, 360364, https://doi.org/10.1038/nclimate1229.

    • Crossref
    • 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, https://doi.org/10.1175/1520-0442(2000)013<3551:OOWWVC>2.0.CO;2.

    • Crossref
    • 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, https://doi.org/10.1175/1520-0485(2001)031<1324:IVIWWV>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Meinen, C. S., M. J. McPhaden, and G. C. Johnson, 2001: Vertical velocities and transports in the equatorial Pacific during 1993–99. J. Phys. Oceanogr., 31, 32303248, https://doi.org/10.1175/1520-0485(2001)031<3230:VVATIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Menkes, C. E., M. Lengaigne, J. Vialard, M. Puy, P. Marchesiello, S. Cravatte, and G. Cambon, 2014: About the role of westerly wind events in the possible development of an El Niño in 2014. Geophys. Res. Lett., 41, 64766483, https://doi.org/10.1002/2014GL061186.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Morice, C. P., J. J. Kennedy, N. A. Rayner, and P. D. Jones, 2012: Quantifying uncertainties in global and regional temperature change using an ensemble of observational estimates: The HadCRUT4 data set. J. Geophys. Res., 117, D08101, https://doi.org/10.1029/2011JD017187.

    • Search Google Scholar
    • Export Citation
  • Moum, J. N., A. Perlin, J. D. Nash, and M. J. McPhaden, 2013: Seasonal sea surface cooling in the equatorial Pacific cold tongue controlled by ocean mixing. Nature, 500, 6467, https://doi.org/10.1038/nature12363.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Neske, S., and S. McGregor, 2018: Understanding the warm water volume precursor of ENSO events and its interdecadal variation. Geophys. Res. Lett., 45, 15771585, https://doi.org/10.1002/2017GL076439.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Okumura, Y. M., and C. Deser, 2010: Asymmetry in the duration of El Niño and La Niña. J. Climate, 23, 58265843, https://doi.org/10.1175/2010JCLI3592.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pham, H. T., W. D. Smyth, S. Sarkar, and J. N. Moum, 2017: Seasonality of deep cycle turbulence in the eastern equatorial Pacific. J. Phys. Oceanogr., 47, 21892209, https://doi.org/10.1175/JPO-D-17-0008.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rayner, N., D. E. Parker, E. Horton, C. Folland, L. Alexander, D. Rowell, E. Kent, and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108, 4407, https://doi.org/10.1029/2002JD002670.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Redi, M. H., 1982: Oceanic isopycnal mixing by coordinate rotation. J. Phys. Oceanogr., 12, 11541158, https://doi.org/10.1175/1520-0485(1982)012<1154:OIMBCR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Reynolds, R. W., T. M. Smith, C. Liu, D. B. Chelton, K. S. Casey, and M. G. Schlax, 2007: Daily high-resolution-blended analyses for sea surface temperature. J. Climate, 20, 54735496, https://doi.org/10.1175/2007JCLI1824.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roemmich, D., and J. Gilson, 2011: The global ocean imprint of ENSO. Geophys. Res. Lett., 38, L13606, https://doi.org/10.1029/2011GL047992.

  • Schott, F. A., J. P. McCreary Jr., and G. C. Johnson, 2004: Shallow overturning circulations of the tropical-subtropical oceans. Earth’s Climate, 147, 261304, https://doi.org/10.1029/147GM15.

    • Search Google Scholar
    • Export Citation
  • Shinoda, T., W. Han, E. J. Metzger, and H. E. Hurlburt, 2012: Seasonal variation of the Indonesian Throughflow in Makassar Strait. J. Phys. Oceanogr., 42, 10991123, https://doi.org/10.1175/JPO-D-11-0120.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Smith, T. M., and R. W. Reynolds, 2003: Extended reconstruction of global sea surface temperatures based on COADS data (1854–1997). J. Climate, 16, 14951510, https://doi.org/10.1175/1520-0442-16.10.1495.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Smyth, W. D., and J. N. Moum, 2013: Marginal instability and deep cycle turbulence in the eastern equatorial Pacific Ocean. Geophys. Res. Lett., 40, 61816185, https://doi.org/10.1002/2013GL058403.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Spence, P., R. M. Holmes, A. M. Hogg, S. M. Griffies, K. D. Stewart, and M. H. England, 2017: Localized rapid warming of West Antarctic subsurface waters by remote winds. Nat. Climate Change, 7, 595603, https://doi.org/10.1038/nclimate3335.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sprintall, J., and A. Révelard, 2014: The Indonesian Throughflow response to Indo-Pacific climate variability. J. Geophys. Res. Oceans, 119, 11611175, https://doi.org/10.1002/2013JC009533.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stewart, K., A. M. Hogg, S. Griffies, A. Heerdegen, M. Ward, P. Spence, and M. England, 2017: Vertical resolution of baroclinic modes in global ocean models. Ocean Modell., 113, 5065, https://doi.org/10.1016/j.ocemod.2017.03.012.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stuecker, M. F., A. Timmermann, F.-F. Jin, S. McGregor, and H.-L. Ren, 2013: A combination mode of the annual cycle and the El Niño/Southern Oscillation. Nat. Geosci., 6, 540544, https://doi.org/10.1038/ngeo1826.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stuecker, M. F., F.-F. Jin, A. Timmermann, and S. McGregor, 2015: Combination mode dynamics of the anomalous northwest Pacific anticyclone. J. Climate, 28, 10931111, https://doi.org/10.1175/JCLI-D-14-00225.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Suarez, M. J., and P. S. Schopf, 1988: A delayed action oscillator for ENSO. J. Atmos. Sci., 45, 32833287, https://doi.org/10.1175/1520-0469(1988)045<3283:ADAOFE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Timmermann, A., and et al. , 2018: El Niño–Southern Oscillation complexity. Nature, 559, 535545, https://doi.org/10.1038/s41586-018-0252-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., J. M. Caron, D. P. Stepaniak, and S. Worley, 2002: Evolution of El Niño–Southern Oscillation and global atmospheric surface temperatures. J. Geophys. Res., 107, 4065, https://doi.org/10.1029/2000JD000298.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and et al. , 2007: Observations: Surface and atmospheric climate change. Climate Change 2007: The Physical Science Basis, S. Solomon et al., Eds., Cambridge University Press, 235–336.

  • Tsujino, H., and et al. , 2018: JRA-55 based surface dataset for driving ocean–sea-ice models (JRA55-do). Ocean Modell., 130, 79139, https://doi.org/10.1016/j.ocemod.2018.07.002.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Walin, G., 1982: On the relation between sea-surface heat flow and thermal circulation in the ocean. Tellus, 34, 187195, https://doi.org/10.3402/tellusa.v34i2.10801.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Warner, S. J., and J. N. Moum, 2019: Feedback of mixing to ENSO phase change. Geophys. Res. Lett., 46, 13 92013 927, https://doi.org/10.1029/2019GL085415.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wu, Q., X. Zhang, J. A. Church, and J. Hu, 2019: ENSO-related global ocean heat content variations. J. Climate, 32, 4568, https://doi.org/10.1175/JCLI-D-17-0861.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wyrtki, K., 1975: El Niño—The dynamic response of the equatorial Pacific Ocean to atmospheric forcing. J. Phys. Oceanogr., 5, 572584, https://doi.org/10.1175/1520-0485(1975)005<0572:ENTDRO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wyrtki, K., 1985: Water displacements in the Pacific and the genesis of El Niño cycles. J. Geophys. Res., 90, 71297132, https://doi.org/10.1029/JC090iC04p07129.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zeller, M., S. McGregor, and P. Spence, 2019: Hemispheric asymmetry of the Pacific shallow meridional overturning circulation. J. Geophys. Res. Oceans, 124, 57655786, https://doi.org/10.1029/2018JC014840.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zuo, H., M. Balmaseda, K. Mogensen, and S. Tietsche, 2018: OCEAN5: The ECMWF Ocean Reanalysis System and its real-time analysis component. European Centre for Medium-Range Weather Forecasts, 44 pp.

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Key Role of Diabatic Processes in Regulating Warm Water Volume Variability over ENSO Events

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  • 1 Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • | 2 Climate Change Research Centre, and ARC Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales, Australia
  • | 3 School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales, Australia
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Abstract

The equatorial Pacific warm water volume (WWV), defined as the volume of water warmer than 20°C near the equator, is a key predictor for El Niño–Southern Oscillation (ENSO), and yet much about the individual processes that influence it remains unknown. In this study, we conduct idealized ENSO simulations forced with symmetric El Niño– and La Niña–associated atmospheric anomalies as well as a historical 1979–2016 hindcast simulation. We use the water mass transformation framework to examine the individual contributions of diabatic and adiabatic processes to changes in WWV. We find that in both sets of simulations, El Niño’s discharge and La Niña’s recharge periods are initiated by diabatic fluxes of volume across the 20°C isotherm associated with changes in surface forcing and vertical mixing. Changes in adiabatic horizontal volume transport above 20°C between the equator and subtropical latitudes dominate at a later stage. While surface forcing and vertical mixing deplete WWV during El Niño, surface forcing during La Niña drives a large increase partially compensated for by a decrease driven by vertical mixing. On average, the ratio of diabatic to adiabatic contributions to changes in WWV during El Niño is about 40% to 60%; during La Niña this ratio changes to 75% to 25%. The increased importance of the diabatic processes during La Niña, especially the surface heat fluxes, is linked to the shoaling of the 20°C isotherm in the eastern equatorial Pacific and is a major source of asymmetry between the two ENSO phases, even in the idealized simulations where the wind forcing and adiabatic fluxes are symmetric.

Corresponding author: Maurice F. Huguenin, m.huguenin-virchaux@unsw.edu.au

Abstract

The equatorial Pacific warm water volume (WWV), defined as the volume of water warmer than 20°C near the equator, is a key predictor for El Niño–Southern Oscillation (ENSO), and yet much about the individual processes that influence it remains unknown. In this study, we conduct idealized ENSO simulations forced with symmetric El Niño– and La Niña–associated atmospheric anomalies as well as a historical 1979–2016 hindcast simulation. We use the water mass transformation framework to examine the individual contributions of diabatic and adiabatic processes to changes in WWV. We find that in both sets of simulations, El Niño’s discharge and La Niña’s recharge periods are initiated by diabatic fluxes of volume across the 20°C isotherm associated with changes in surface forcing and vertical mixing. Changes in adiabatic horizontal volume transport above 20°C between the equator and subtropical latitudes dominate at a later stage. While surface forcing and vertical mixing deplete WWV during El Niño, surface forcing during La Niña drives a large increase partially compensated for by a decrease driven by vertical mixing. On average, the ratio of diabatic to adiabatic contributions to changes in WWV during El Niño is about 40% to 60%; during La Niña this ratio changes to 75% to 25%. The increased importance of the diabatic processes during La Niña, especially the surface heat fluxes, is linked to the shoaling of the 20°C isotherm in the eastern equatorial Pacific and is a major source of asymmetry between the two ENSO phases, even in the idealized simulations where the wind forcing and adiabatic fluxes are symmetric.

Corresponding author: Maurice F. Huguenin, m.huguenin-virchaux@unsw.edu.au
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