Subduction and Transport in the Indian and Pacific Oceans in a 2 × CO2 Climate

Oleg A. Saenko Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada

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Xiao-Yi Yang Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada, and College of Oceanography and Environmental Science, Xiamen University, Xiamen, China

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Matthew H. England Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia

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Warren G. Lee Candian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada

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Abstract

Subduction, water mass transformation, and transport rates in the Indo-Pacific Ocean are diagnosed in a recent version of the Canadian Centre for Climate Modelling and Analysis coupled model. It is found that the subduction across the base of the winter mixed layer is dominated by the lateral transfer, particularly within the relatively dense water classes corresponding to the densest mode and intermediate waters. However, within lighter densities, including those characterizing the lighter varieties of mode waters, the vertical transfer has a strong positive input to the net subduction. The upper-ocean volume transports across 30°N and 32°S are largest within the density classes that correspond to mode waters. In the North Pacific, the buoyancy flux converts the near-surface waters mostly to denser water classes, whereas in the Southern Ocean the surface waters are transformed both to lighter and denser water classes, depending on the density. In response to a doubling of CO2, the subduction, transformation, and transport of mode waters in both hemispheres shift to lighter densities but do not change significantly, whereas the subduction of intermediate waters decreases. The area of large winter mixed layer depths decreases, particularly in the Southern Hemisphere. In the low latitudes, the thermocline water flux that enters the tropical Pacific via the western boundary flows generally increases. However, its anomaly has a complex structure, so that integrated estimates can be sensitive to the isopycnal ranges. The upper part of the Equatorial Undercurrent (EUC) strengthens in the warmer climate, whereas its lower part weakens. The anomaly in the EUC closely follows the anomaly in stratification along the equator. The Indonesian Throughflow transport decreases with part of it being redirected eastward. This part joins with the intensified equatorward thermocline flows at the western boundaries and contributes to the EUC anomaly.

Corresponding author address: Oleg A. Saenko, Canadian Centre for Climate Modelling and Analysis, University of Victoria, P.O. Box 3065 STN CSC, Victoria BC V8W 3V6, Canada. Email: oleg.saenko@ec.gc.ca

Abstract

Subduction, water mass transformation, and transport rates in the Indo-Pacific Ocean are diagnosed in a recent version of the Canadian Centre for Climate Modelling and Analysis coupled model. It is found that the subduction across the base of the winter mixed layer is dominated by the lateral transfer, particularly within the relatively dense water classes corresponding to the densest mode and intermediate waters. However, within lighter densities, including those characterizing the lighter varieties of mode waters, the vertical transfer has a strong positive input to the net subduction. The upper-ocean volume transports across 30°N and 32°S are largest within the density classes that correspond to mode waters. In the North Pacific, the buoyancy flux converts the near-surface waters mostly to denser water classes, whereas in the Southern Ocean the surface waters are transformed both to lighter and denser water classes, depending on the density. In response to a doubling of CO2, the subduction, transformation, and transport of mode waters in both hemispheres shift to lighter densities but do not change significantly, whereas the subduction of intermediate waters decreases. The area of large winter mixed layer depths decreases, particularly in the Southern Hemisphere. In the low latitudes, the thermocline water flux that enters the tropical Pacific via the western boundary flows generally increases. However, its anomaly has a complex structure, so that integrated estimates can be sensitive to the isopycnal ranges. The upper part of the Equatorial Undercurrent (EUC) strengthens in the warmer climate, whereas its lower part weakens. The anomaly in the EUC closely follows the anomaly in stratification along the equator. The Indonesian Throughflow transport decreases with part of it being redirected eastward. This part joins with the intensified equatorward thermocline flows at the western boundaries and contributes to the EUC anomaly.

Corresponding author address: Oleg A. Saenko, Canadian Centre for Climate Modelling and Analysis, University of Victoria, P.O. Box 3065 STN CSC, Victoria BC V8W 3V6, Canada. Email: oleg.saenko@ec.gc.ca

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  • Banks, H., R. Wood, and J. Gregory, 2002: Changes to Indian Ocean Subantarctic Mode Water in a coupled climate model as CO2 forcing increases. J. Phys. Oceanogr., 32 , 28162827.

    • Search Google Scholar
    • Export Citation
  • 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. McDougall, 1991: A model of sea level rise caused by ocean thermal expansion. J. Climate, 4 , 438456.

    • Search Google Scholar
    • Export Citation
  • Downes, S. M., N. L. Bindoff, and S. R. Rintoul, 2009: Impacts of climate change on the subduction of mode and intermediate water masses in the Southern Ocean. J. Climate, 22 , 32893302.

    • Search Google Scholar
    • Export Citation
  • England, M. H., and F. Huang, 2005: On the interannual variability of the Indonesian Throughflow and its linkage with ENSO. J. Climate, 18 , 14351444.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Flato, G. M., G. J. Boer, W. G. Lee, N. A. McFarlane, D. Ramsden, M. C. Reader, and A. J. Weaver, 2000: The Canadian Centre for Climate Modelling and Analysis global coupled model and its climate. Climate Dyn., 16 , 451467.

    • Search Google Scholar
    • Export Citation
  • Ganachaud, A., and C. Wunsch, 2003: Large-scale ocean heat and freshwater transports during the World Ocean Circulation Experiment. J. Climate, 16 , 696705.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean general circulation models. J. Phys. Oceanogr., 20 , 150155.

  • Gill, A. E., 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

  • Goes, M., I. Wainer, P. R. Gent, and F. O. Bryan, 2008: Changes in subduction in the South Atlantic Ocean during the 21st century in the CCSM3. Geophys. Res. Lett., 35 , L06701. doi:10.1029/2007GL032762.

    • Search Google Scholar
    • Export Citation
  • Gordon, A. L., 2001: Interocean exchange. Ocean Circulation and Climate: Observing and Modelling the Global Ocean, G. Siedler, J. Church, and J. Gould, Eds., International Geophysics Series, Vol. 77, Academic Press, 303–314.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Hanawa, K., and L. Talley, 2001: Mode waters. Ocean Circulation and Climate: Observing and Modelling the Global Ocean, G. Siedler, J. Church, and J. Gould, Eds., International Geophysics Series, Vol. 77, Academic Press, 373–386.

    • Search Google Scholar
    • Export Citation
  • Hautala, S., and D. Roemmich, 1998: Subtropical mode water in the northeast Pacific Basin. J. Geophys. Res., 103 , 1305513066.

  • Karstensen, J., and D. Quadfasel, 2002: Formation of Southern Hemisphere thermocline waters: Water mass conversion and subduction. J. Phys. Oceanogr., 32 , 30203038.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., J. C. McWilliams, and S. C. Doney, 1994: Oceanic vertical mixing: A review and a model with a nonlocal boundary layer parameterization. Rev. Geophys., 32 , 363403.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., G. Danabasoglu, J. C. McWilliams, P. R. Gent, and F. O. Bryan, 2001: Equatorial circulation of a global ocean climate model with anisotropic horizontal viscosity. J. Phys. Oceanogr., 31 , 518536.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., and T. P. Boyer, 1994: Temperature. Vol. 4, World Ocean Atlas 1994, NOAA Atlas NESDIS 4, 117 pp.

  • Levitus, S., R. Burgett, and T. P. Boyer, 1994: Salinity. Vol. 3, World Ocean Atlas 1994, NOAA Atlas NESDIS 3, 99 pp.

  • Liu, Z., and S. G. H. Philander, 1995: How different wind stress patterns affect the tropical–subtropical circulations of the upper ocean. J. Phys. Oceanogr., 25 , 449462.

    • Search Google Scholar
    • Export Citation
  • Liu, Z., S. G. H. Philander, and R. C. Pacanowski, 1994: A GCM study of the tropical–subtropical upper-ocean water exchange. J. Phys. Oceanogr., 24 , 26062623.

    • Search Google Scholar
    • Export Citation
  • Lohmann, K., and M. Latif, 2005: Tropical Pacific decadal variability and the subtropical–tropical cells. J. Climate, 18 , 51635178.

    • Search Google Scholar
    • Export Citation
  • Luo, Y., Q. Liu, and L. M. Rothstein, 2009a: Simulated response of North Pacific Mode Waters to global warming. Geophys. Res. Lett., 36 , L23609. doi:10.1029/2009GL040906.

    • Search Google Scholar
    • Export Citation
  • Luo, Y., L. M. Rothstein, and R.-H. Zhang, 2009b: Response of Pacific subtropical-tropical thermocline water pathways and transports to global warming. Geophys. Res. Lett., 36 , L04601. doi:10.1029/2008GL036705.

    • Search Google Scholar
    • Export Citation
  • Marshall, J. C., A. J. G. Nurser, and R. G. Williams, 1993: Inferring the subduction rate and period over the North Atlantic. J. Phys. Oceanogr., 23 , 13151329.

    • Search Google Scholar
    • Export Citation
  • Marshall, J. C., D. Jamous, and J. Nilsson, 1999: Reconciling thermodynamic and dynamic methods of computation of water-mass transformation rates. Deep-Sea Res., 46A , 545572.

    • Search Google Scholar
    • Export Citation
  • Masuzawa, J., 1969: Subtropical mode water. Deep-Sea Res., 16 , 463472.

  • McCartney, M. S., 1977: Subantarctic Mode Water. Deep-Sea Res., 24 , (Suppl.). 103119.

  • McCreary, J. P., and P. Lu, 1994: On the interaction between the subtropical and the equatorial oceans: The subtropical cell. Phys. Oceanogr., 24 , 466497.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Merryfield, W. J., and G. J. Boer, 2005: Variability of upper Pacific Ocean overturning in a coupled climate model. J. Climate, 18 , 666683.

    • Search Google Scholar
    • Export Citation
  • Nakamura, H., 1996: A pycnostad on the bottom of the ventilated portion in the central subtropical North Pacific: Its distribution and formation. J. Oceanogr., 52 , 171188.

    • Search Google Scholar
    • Export Citation
  • Ohno, Y., N. Iwasaka, F. Kobashi, and Y. Sato, 2009: Mixed layer depth climatology of the North Pacific based on Argo observations. J. Oceanogr., 65 , 116.

    • Search Google Scholar
    • Export Citation
  • Park, Y.-G., and K. Bryan, 2000: Comparison of thermally driven circulations from a depth coordinate model and an isopycnal-layer model. Part I: Scaling-law sensitivity to vertical diffusivity. J. Phys. Oceanogr., 30 , 590605.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 1987: An inertial theory of the Equatorial Undercurrent. J. Phys. Oceanogr., 17 , 19781985.

  • Qiu, B., and R. X. Huang, 1995: Ventilation of the North Atlantic and North Pacific: Subduction versus obduction. J. Phys. Oceanogr., 25 , 23742390.

    • Search Google Scholar
    • Export Citation
  • Rintoul, S. R., and M. H. England, 2002: Ekman transport dominates air–sea fluxes in driving variability of Subantarctic Mode Water. J. Phys. Oceanogr., 32 , 13081321.

    • Search Google Scholar
    • Export Citation
  • Saenko, O. A., and W. G. Lee, 2010: Reorganization of the ocean overturning in a colder climate. Geophys. Res. Lett., 37 , L04606. doi:10.1029/2010GL042417.

    • Search Google Scholar
    • Export Citation
  • Saenko, O. A., J. C. Fyfe, and M. H. England, 2005: On the response of the oceanic wind-driven circulation to atmospheric CO2 increase. Climate Dyn., 25 , 415426.

    • Search Google Scholar
    • Export Citation
  • Sallée, J.-B., K. Speer, S. Rintoul, and S. Wijffels, 2010: Southern Ocean thermocline ventilation. J. Phys. Oceanogr., 40 , 509529.

  • Scinocca, J. F., N. A. McFarlane, M. Lazare, J. Li, and D. Plummer, 2008: The CCCma third generation AGCM and its extension into the middle atmosphere. Atmos. Chem. Phys. Discuss., 8 , 78837930.

    • Search Google Scholar
    • Export Citation
  • Sen Gupta, A., A. Santoso, A. S. Taschetto, C. C. Ummenhofer, J. Trevena, and M. H. England, 2009: Projected changes to the Southern Hemisphere ocean and sea ice in the IPCC AR4 climate models. J. Climate, 22 , 30473078.

    • Search Google Scholar
    • Export Citation
  • Shcherbina, A. Y., L. D. Talley, and D. L. Rudnick, 2003: Direct observations of North Pacific ventilation: Brine rejection in the Okhotsk Sea. Science, 302 , 19521955.

    • Search Google Scholar
    • Export Citation
  • Simmons, H. L., S. R. Jayne, L. C. St. Laurent, and A. J. Weaver, 2004: Tidally driven mixing in a numerical model of the ocean general circulation. Ocean Modell., 6 , 245263. doi:10.1016/S1463-5003(03)00011-8.

    • Search Google Scholar
    • Export Citation
  • Speer, K., E. Guilyardi, and G. Madec, 2000: Southern Ocean transformation in a coupled model with and without eddy mass fluxes. Tellus, 52A , 554565.

    • Search Google Scholar
    • Export Citation
  • Sprintall, J., S. E. Wijffels, R. Molcard, and I. Jaya, 2009: Direct estimates of the Indonesian Throughflow entering the Indian Ocean: 2004–2006. J. Geophys. Res., 114 , C07001. doi:10.1029/2008JC005257.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1979: Determination of watermass properties of water pumped down from the Ekman layer to the geostrophic flow below. Proc. Natl. Acad. Sci. USA, 76 , 30513055.

    • Search Google Scholar
    • Export Citation
  • Suga, T., Y. Takei, and K. Hanawa, 1997: Thermostad distribution in the North Pacific subtropical gyre: The Central Mode Water and the Subtropical Mode Water. J. Phys. Oceanogr., 27 , 140152.

    • Search Google Scholar
    • Export Citation
  • Suga, T., K. Motoki, Y. Aoki, and A. MacDonald, 2004: The North Pacific climatology of winter mixed layer and mode waters. J. Phys. Oceanogr., 34 , 322.

    • Search Google Scholar
    • Export Citation
  • Talley, L. D., 1993: Distribution and formation of North Pacific Intermediate Water. J. Phys. Oceanogr., 23 , 517537.

  • Talley, L. D., 2003: Shallow, intermediate, and deep overturning components of the global heat budget. J. Phys. Oceanogr., 33 , 530560.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and J. M. Caron, 2001: Estimates of meridional atmosphere and ocean heat transports. J. Climate, 14 , 34333443.

  • Tsujino, H., and T. Yasuda, 2004: Formation and circulation of mode waters of the North Pacific in a high-resolution GCM. J. Phys. Oceanogr., 34 , 399415.

    • Search Google Scholar
    • Export Citation
  • Wang, D., M. A. Cane, S. Khatiwala, and D. Chen, 2008: Changes of the shallow Pacific meridional overturning circulation under global warming. Eos, Trans. Amer. Geophys. Union, (Fall Meeting Suppl.), Abstract A13B-0255.

    • Search Google Scholar
    • Export Citation
  • Woods, J. D., 1985: The physics of thermocline ventilation. Coupled Ocean-Atmosphere Models, J. C. J. Nihoul, Ed., Oceanography Series, Vol. 40, Elsevier Science Publishers, 543–590.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., T. Kunitani, A. Kubokawa, M. Nonaka, and S. Hosoda, 2000: Interdecadal thermocline variability in the North Pacific for 1958–97: A GCM simulation. J. Phys. Oceanogr., 30 , 27982813.

    • Search Google Scholar
    • Export Citation
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