Comparison of Observed Temperature and Salinity Changes in the Indo-Pacific with Results from the Coupled Climate Model HadCM3: Processes and Mechanisms

Helene T. Banks Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire, United Kingdom

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Nathaniel L. Bindoff Antarctic Co-operative Research Centre, Hobart, Australia

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Abstract

Observed changes in temperature and salinity properties on isopycnals across hydrographic sections throughout the Indo-Pacific are compared with the changes modeled by the coupled climate model, HadCM3. Observations show cooling and freshening on isopycnals in midlatitudes, and there is quantitative agreement between modeled and observed water mass changes on five out of six zonal sections. The full Indo-Pacific pattern of change in the climate model is examined and it is discovered that the pattern of cooling and freshening on isopycnals in midlatitudes, with warming on isopycnals at high latitudes, may be thought of as a fingerprint of anthropogenic forcing. The water mass changes are related to changes in the surface fluxes and it is found that surface warming is the dominant factor in producing water mass changes, although changes in the freshwater cycle are important in the formation zone for Antarctic Intermediate Water. The coupled model has a low-amplitude, low-frequency (100-yr period) internal mode related to the anthropogenic fingerprint. Further observations are required to measure the amplitude of the internal mode as well as the anthropogenically forced mode.

Corresponding author address: Dr. Helene T. Banks, Hadley Centre for Climate Prediction and Research, Met Office, London Road, Bracknell, Berkshire RG12 2SY, United Kingdom. Email: helene.banks@metoffice.com

Abstract

Observed changes in temperature and salinity properties on isopycnals across hydrographic sections throughout the Indo-Pacific are compared with the changes modeled by the coupled climate model, HadCM3. Observations show cooling and freshening on isopycnals in midlatitudes, and there is quantitative agreement between modeled and observed water mass changes on five out of six zonal sections. The full Indo-Pacific pattern of change in the climate model is examined and it is discovered that the pattern of cooling and freshening on isopycnals in midlatitudes, with warming on isopycnals at high latitudes, may be thought of as a fingerprint of anthropogenic forcing. The water mass changes are related to changes in the surface fluxes and it is found that surface warming is the dominant factor in producing water mass changes, although changes in the freshwater cycle are important in the formation zone for Antarctic Intermediate Water. The coupled model has a low-amplitude, low-frequency (100-yr period) internal mode related to the anthropogenic fingerprint. Further observations are required to measure the amplitude of the internal mode as well as the anthropogenically forced mode.

Corresponding author address: Dr. Helene T. Banks, Hadley Centre for Climate Prediction and Research, Met Office, London Road, Bracknell, Berkshire RG12 2SY, United Kingdom. Email: helene.banks@metoffice.com

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  • Aoki, S., 1997: Trends and interannual variability of surface layer temperature in the Indian sector of the Southern Ocean observed by the Japanese Antarctic Research Expeditions. J. Oceanogr., 53 , 623631.

    • Search Google Scholar
    • Export Citation
  • Banks, H. T., and R. A. Wood, 2002: Where to look for anthropogenic climate change in the ocean. J. Climate, 15 , 879891.

  • Banks, H. T., R. A. Wood, J. M. Gregory, T. C. Johns, and G. S. Jones, 2000: Are observed decadal changes in intermediate water masses a signature of anthropogenic climate change? Geophys. Res. Lett., 27 , 29612964.

    • Search Google Scholar
    • Export Citation
  • Banks, H. T., R. A. Wood, and J. M. 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
  • Barnett, T., D. Pierce, and R. Schnur, 2001: Detection of anthropogenic climate change in the world’s oceans. Science, 292 , 270274.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and J. A. Church, 1992: Warming of the water column in the southwest Pacific Ocean. Nature, 357 , 5962.

  • Bindoff, N. L., and C. Wunsch, 1992: Comparison of synoptic and climatologically mapped sections in the South Pacific Ocean. J. Climate, 5 , 631645.

    • 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
  • Bindoff, N. L., and T. J. McDougall, 2000: Decadal changes along an Indian Ocean section at 32°S and their interpretation. J. Phys. Oceanogr., 30 , 12071222.

    • Search Google Scholar
    • Export Citation
  • Bretherton, F. P., R. E. Davis, and C. B. Fandry, 1976: A technique for objective analysis and design of oceanographic experiments applied to MODE-73. Deep-Sea Res., 23 , 559582.

    • Search Google Scholar
    • Export Citation
  • Cox, M. D., 1984: A primitive equation, three dimensional model of the ocean. Ocean Group Tech. Rep. 1, GFDL, Princeton, NJ, 143 pp.

  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20 , 150155.

  • Gordon, A., E. J. Molinelli, and T. N. Baker, 1982: Southern Ocean Atlas. Columbia University Press, 35 pp. plus 248 pl.

  • Gordon, C., C. Cooper, C. A. Senior, H. Banks, J. M. Gregory, T. C. Johns, J. F. B. Mitchell, and R. A. Wood, 2000: The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Climate Dyn., 16 , 147168.

    • Search Google Scholar
    • Export Citation
  • Guiot, J., J. J. Boreux, P. Braconnot, and F. Torre, 1999: Data-model comparison in paleoclimatology. Climate Dyn., 15 , 569581.

  • Houghton, J. T., Y. Ding, D. J. Griggs, M. Noguer, P. J. van der Linden, D. Xiaosu, and K. Maskell, Eds.,. 2001: Climate Change 2001: The Scientific Basis. Cambridge University Press, 881 pp.

    • Search Google Scholar
    • Export Citation
  • Johns, T. C., R. E. Carnell, J. F. Crossley, J. M. Gregory, J. F. B. Mitchell, C. A. Senior, S. F. B. Tett, and R. A. Wood, 1997: The second Hadley Centre coupled ocean–atmosphere GCM: Model description, spinup and validation. Climate Dyn., 13 , 103134.

    • Search Google Scholar
    • Export Citation
  • Johns, T. C,, and Coauthors. 2001: Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Hadley Centre Tech. Note 22, 61 pp.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., and A. H. Orsi, 1997: Southwest Pacific Ocean water-mass changes between 1968/69 and 1990/91. J. Climate, 10 , 306316.

    • 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,, and Coauthors. 1998: Introduction. Vol. 1, World Ocean Database 1998, NOAA Atlas NESDIS 18, 346 pp.

  • Levitus, S., J. Antonov, J. Wang, T. Delworth, K. Dixon, and A. Broccoli, 2001: Anthropogenic warming of the earth’s climate system. Science, 292 , 267270.

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

    • Search Google Scholar
    • Export Citation
  • Roemmich, D., 1983: Optimal estimation of hydrographic station data and derived fields. J. Phys. Oceanogr., 13 , 15441549.

  • Santer, B. D., U. Mikolajewicz, W. Bruggemann, U. Cubasch, K. Hasselmann, H. Hock, E. Maier-Reimer, and T. M. L. Wigley, 1995: Ocean variability and its influence on the detectability of greenhouse warming signals. J. Geophys. Res., 100 , 1069310725.

    • Search Google Scholar
    • Export Citation
  • Wilson, S., 2000: Launching the Argo armada. Oceanus, 42 , 1719.

  • Wong, A., N. L. Bindoff, and J. A. Church, 1999: Large-scale freshening of intermediate waters in the Pacific and Indian Oceans. Nature, 400 , 440443.

    • Search Google Scholar
    • Export Citation
  • Wong, A., N. L. Bindoff, and J. A. Church, 2001: Freshwater and heat changes in the North and South Pacific Oceans between the 1960s and 1985–94. J. Climate, 14 , 16131633.

    • Search Google Scholar
    • Export Citation
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