• Broecker, W. S., T.-H. Peng, G. Ostlund, and M. Stuiver, 1985: The distribution of bomb radiocarbon in the ocean. J. Geophys. Res., 90, 69536970, https://doi.org/10.1029/JC090iC04p06953.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Broecker, W. S., S. Sutherland, W. Smethie, T.-H. Peng, and G. Ostlund, 1995: Oceanic radiocarbon: Separation of the natural and bomb components. Global Biogeochem. Cycles, 9, 263288, https://doi.org/10.1029/95GB00208.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Druffel, E. R. M., 1987: Bomb radiocarbon in the Pacific: Annual and seasonal timescale variations. J. Mar. Res., 45, 667698, https://doi.org/10.1357/002224087788326876.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Farneti, R., S. Dwivedi, F. Kucharski, F. Molteni, and S. M. Griffies, 2014: On Pacific subtropical cell variability over the second half of the twentieth century. J. Climate, 27, 71027112, https://doi.org/10.1175/JCLI-D-13-00707.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fine, R. A., W. H. Peterson, and H. G. Ostlund, 1987: The penetration of tritium into the tropical Pacific. J. Phys. Oceanogr., 17, 553564, https://doi.org/10.1175/1520-0485(1987)017<0553:TPOTIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fukumori, I., T. Lee, B. Cheng, and D. Menemenlis, 2004: The origin, pathway, and destination of Nino-3 water estimated by a simulated passive tracer and its adjoint. J. Phys. Oceanogr., 34, 582604, https://doi.org/10.1175/2515.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Giese, B. S., S. C. Urizar, and N. S. Fučkar, 2002: Southern Hemisphere origins of the 1976 climate shift. Geophys. Res. Lett., 29, 1014, https://doi.org/10.1029/2001GL013268.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Goodman, P. J., W. Hazeleger, P. de Vries, and M. Cane, 2005: Pathways into the Pacific Equatorial Undercurrent: A trajectory analysis. J. Phys. Oceanogr., 35, 21342151, https://doi.org/10.1175/JPO2825.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grenier, M., S. Cravatte, B. Blanke, C. Menkes, A. Koch-Larrouy, F. Durand, A. Melet, and C. Jeandel, 2011: From the western boundary currents to the Pacific Equatorial Undercurrent: Modeled pathways and water mass evolution. J. Geophys. Res., 116, C12044, https://doi.org/10.1029/2011JC007477.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gu, D., and S. G. H. Philander, 1997: Interdecadal climate fluctuations that depend on exchanges between the tropics and extratropics. Science, 275, 805807, https://doi.org/10.1126/science.275.5301.805.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hazeleger, W., M. Visbeck, M. Cane, A. Karspeck, and N. Naik, 2001: Decadal upper ocean temperature variability in the tropical Pacific. J. Geophys. Res., 106, 89718988, https://doi.org/10.1029/2000JC000536.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Izumo, T., J. Picaut, and B. Blanke, 2002: Tropical pathways, equatorial undercurrent variability and the 1998 La Nina. Geophys. Res. Lett., 29, 2080, https://doi.org/10.1029/2002GL015073.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., and M. J. McPhaden, 1999: Interior pycnocline flow from the subtropical to equatorial Pacific Ocean. J. Phys. Oceanogr., 29, 30733089, https://doi.org/10.1175/1520-0485(1999)029<3073:IPFFTS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., M. J. McPhaden, and E. Firing, 2001: Equatorial Pacific Ocean horizontal velocity, divergence, and upwelling. J. Phys. Oceanogr., 31, 839849, https://doi.org/10.1175/1520-0485(2001)031<0839:EPOHVD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., B. M. Sloyan, W. S. Kessler, and K. E. McTaggart, 2002: Direct measurements of upper ocean currents and water properties across the tropical Pacific during the 1990s. Prog. Oceanogr., 52, 3161, https://doi.org/10.1016/S0079-6611(02)00021-6.

    • Crossref
    • 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, https://doi.org/10.1029/1999GL900352.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kolodziejczyk, N., and F. Gaillard, 2012: Observation of spiciness interannual variability in the Pacific pycnocline. J. Geophys. Res., 117, C12018, https://doi.org/10.1029/2012JC008365.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kosaka, Y., and S. P. Xie, 2013: Recent global-warming hiatus tied to equatorial Pacific surface cooling. Nature, 501, 403407, https://doi.org/10.1038/nature12534.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lee, T., I. Fukumori, D. Menemenlis, Z. Xing, and L. L. Fu, 2002: Effects of the Indonesian Throughflow on the Pacific and Indian Oceans. J. Phys. Oceanogr., 32, 14041429, https://doi.org/10.1175/1520-0485(2002)032<1404:EOTITO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lu, P., and J. P. McCreary, 1995: Influence of the ITCZ on the flow of thermocline water from the subtropical to the equatorial Pacific Ocean. J. Phys. Oceanogr., 25, 30763088, https://doi.org/10.1175/1520-0485(1995)025<3076:IOTIOT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Luyten, J. R., J. Pedlosky, and H. Strommel, 1983: The ventilated thermocline. J. Phys. Oceanogr., 13, 292309, https://doi.org/10.1175/1520-0485(1983)013<0292:TVT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McCreary, J. P., and P. Lu, 1994: Interaction between the subtropical and equatorial ocean circulations: The subtropical cell. J. Phys. Oceanogr., 24, 466497, https://doi.org/10.1175/1520-0485(1994)024<0466:IBTSAE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., and D. Zhang, 2002: Slowdown of the meridional overturning circulation in the upper Pacific Ocean. Nature, 415, 603608, https://doi.org/10.1038/415603a.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., and D. Zhang, 2004: Pacific Ocean circulation rebounds. Geophys. Res. Lett., 31, L18301, https://doi.org/10.1029/2004GL020727.

  • Pedlosky, J., 1987: An inertial theory of the Equatorial Undercurrent. J. Phys. Oceanogr., 17, 19781985, https://doi.org/10.1175/1520-0485(1987)017<1978:AITOTE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Qin, X., A. S. Gupta, and E. van Sebille, 2015: Variability in the origins and pathways of Pacific Equatorial Undercurrent water. J. Geophys. Res., 120, 31133128, https://doi.org/10.1002/2014JC010549.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rodgers, K. B., M. A. Cane, N. H. Naik, and D. P. Schrag, 1999: The role of the Indonesian Throughflow in equatorial Pacific thermocline ventilation. J. Geophys. Res., 104, 20 55120 570, https://doi.org/10.1029/1998JC900094.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rodgers, K. B., D. P. Schrag, M. A. Cane, and N. H. Naik, 2000: The bomb 14C transient in the Pacific Ocean. J. Geophys. Res., 105, 84898512, https://doi.org/10.1029/1999JC900228.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rodgers, K. B., B. Blanke, G. Madec, O. Aumont, P. Ciais, and J.-C. Dutay, 2003: Extratropical sources of equatorial Pacific upwelling in an OGCM. Geophys. Res. Lett., 30, 1084, https://doi.org/10.1029/2002GL016003.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roemmich, D., and J. Gilson, 2009: The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Prog. Oceanogr., 82, 81100, https://doi.org/10.1016/j.pocean.2009.03.004.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roemmich, D., and J. Gilson, 2017: Roemmich–Gilson Argo climatology. Scripps Institution of Oceanography. Subset used: January 2004–December 2016, accessed 31 March 2017, http://sio-argo.ucsd.edu/RG_Climatology.html.

  • Schneider, N., A. J. Miller, M. A. Alexander, and C. Deser, 1999a: Subduction of decadal North Pacific temperature anomalies: Observations and dynamics. J. Phys. Oceanogr., 29, 10561070, https://doi.org/10.1175/1520-0485(1999)029<1056:SODNPT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schneider, N., S. Venzke, A. J. Miller, D. W. Pierce, T. P. Barnett, C. Deser, and M. Latif, 1999b: Pacific thermocline bridge revisited. Geophys. Res. Lett., 26, 13291332, https://doi.org/10.1029/1999GL900222.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • TAO Project Office, 2000: Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network. NOAA/PMEL, accessed 21 July 2016, https://www.pmel.noaa.gov/tao/drupal/disdel/.

  • Thomas, M. D., and A. V. Fedorov, 2017: The eastern subtropical Pacific origin of the equatorial cold bias in climate models: A Lagrangian perspective. J. Climate, 30, 58855900, https://doi.org/10.1175/JCLI-D-16-0819.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Toole, J. M., E. Zou, and R. C. Millard, 1988: On the circulation of the upper waters in the western equatorial Pacific Ocean. Deep-Sea Res., 35, 14511482, https://doi.org/10.1016/0198-0149(88)90097-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tsuchiya, M., R. Lukas, R. A. Fine, E. Firing, and E. Lindstrom, 1989: Source waters of the Pacific Equatorial Undercurrent. Prog. Oceanogr., 23, 101147, https://doi.org/10.1016/0079-6611(89)90012-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, D., and M. J. McPhaden, 2006: Decadal variability of the shallow Pacific meridional overturning circulation: Relation to tropical sea surface temperatures in observations and climate change models. Ocean Modell., 15, 250273, https://doi.org/10.1016/j.ocemod.2005.12.005.

    • Crossref
    • Search Google Scholar
    • Export Citation
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Hemispheric Asymmetry in the Ventilated Thermocline of the Tropical Pacific

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  • 1 Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts
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Abstract

To understand sources of variability in the eastern equatorial Pacific, a region integral to modulating global temperatures, the waters upwelling from the Equatorial Undercurrent (EUC) are characterized. Past work is updated using temperature and salinity measurements from the Argo array and current measurements from Tropical Atmosphere Ocean (TAO) buoys. A larger hemispheric asymmetry is found in the water mass contribution through the ventilated thermocline to the EUC than previously reported, with 80%–90% of waters in the western Pacific originating from the Southern Hemisphere. South Pacific subtropical waters are the dominant source feeding the EUC, although in the central equatorial Pacific upper layers of the EUC experience freshening due to the addition of North Pacific waters. Anomalous volume transport, advection of anomalous waters, and shifts in hemispheric contributions contribute to variability in the EUC. These results suggest that variability in the EUC caused by anomalies in the South Pacific ventilated thermocline can explain variability in the eastern equatorial Pacific.

Supplemental information related to this paper is available at the Journals Online website: https://doi.org/10.1175/JCLI-D-17-0686.s1.

© 2018 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Lauren Kuntz, lkuntz@fas.harvard.edu

Abstract

To understand sources of variability in the eastern equatorial Pacific, a region integral to modulating global temperatures, the waters upwelling from the Equatorial Undercurrent (EUC) are characterized. Past work is updated using temperature and salinity measurements from the Argo array and current measurements from Tropical Atmosphere Ocean (TAO) buoys. A larger hemispheric asymmetry is found in the water mass contribution through the ventilated thermocline to the EUC than previously reported, with 80%–90% of waters in the western Pacific originating from the Southern Hemisphere. South Pacific subtropical waters are the dominant source feeding the EUC, although in the central equatorial Pacific upper layers of the EUC experience freshening due to the addition of North Pacific waters. Anomalous volume transport, advection of anomalous waters, and shifts in hemispheric contributions contribute to variability in the EUC. These results suggest that variability in the EUC caused by anomalies in the South Pacific ventilated thermocline can explain variability in the eastern equatorial Pacific.

Supplemental information related to this paper is available at the Journals Online website: https://doi.org/10.1175/JCLI-D-17-0686.s1.

© 2018 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Lauren Kuntz, lkuntz@fas.harvard.edu

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