• Bond, G., W. Broecker, S. Johnsen, J. McManus, L. Labeyrie, J. Jouzel, and G. Bonani, 1993: Correlations between climate records from North Atlantic sediments and Greenland ice. Nature, 365, 143147.

    • Search Google Scholar
    • Export Citation
  • Bower, A., and H. Hunt, 2000a: Lagrangian observations of the deep western boundary current in the North Atlantic Ocean. Part I: Large-scale pathways and spreading rates. J. Phys. Oceanogr., 30, 764783.

    • Search Google Scholar
    • Export Citation
  • Bower, A., and H. Hunt, 2000b: Lagrangian observations of the deep western boundary current in the North Atlantic Ocean. Part II: The Gulf Stream–deep western boundary current crossover. J. Phys. Oceanogr., 30, 784804.

    • Search Google Scholar
    • Export Citation
  • Bower, A., M. Lozier, S. Gary, and C. Böning, 2009: Interior pathways of the North Atlantic meridional overturning circulation. Nature, 459, 243248.

    • Search Google Scholar
    • Export Citation
  • Bryan, F., and R. Smith, 1998: Modelling the North Atlantic circulation: From eddy-resolving to eddy-permitting. International WOCE Newsletter, No. 33, WOCE International Project Office, Southampton, United Kingdom, 12–14.

    • Search Google Scholar
    • Export Citation
  • Bryan, K., 1991: Poleward heat transport in the ocean. Tellus, 43, 104115.

  • Bryan, K., S. Manabe, and C. Pacanowski, 1975: A global ocean-atmosphere climate model. Part II. The oceanic circulation. J. Phys. Oceanogr., 5, 3046.

    • Search Google Scholar
    • Export Citation
  • Dickson, R., W. Gould, and T. J. Müeller, and C. Maillard, 1985: Estimates of the mean circulation in the deep (>2,000 m) layer of the eastern North Atlantic. Prog. Oceanogr., 14, 103127.

    • Search Google Scholar
    • Export Citation
  • Ducet, N., P. L. Traon, and G. Reverdin, 2000: Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2. J. Geophys. Res., 105, 477498.

    • Search Google Scholar
    • Export Citation
  • Dukowicz, J., and R. Smith, 1994: Implicit free-surface method for the Bryan-Cox-Semtner ocean model. J. Geophys. Res., 99 (C4), 79918014.

    • Search Google Scholar
    • Export Citation
  • Fanning, A. F., and A. J. Weaver, 1997: A horizontal resolution and parameter sensitivity study of heat transport in an idealized coupled climate model. J. Climate, 10, 24692478.

    • Search Google Scholar
    • Export Citation
  • Fischer, J., and F. A. Schott, 2002: Labrador Sea Water tracked by profiling floats—From the boundary current into the open North Atlantic. J. Phys. Oceanogr., 32, 573584.

    • Search Google Scholar
    • Export Citation
  • Flatau, M., L. Talley, and P. Niiler, 2003: The North Atlantic Oscillation, surface current velocities and SST changes in the subpolar North Atlantic. J. Climate, 16, 23552369.

    • Search Google Scholar
    • Export Citation
  • FRAM Group, 1991: An eddy-resolving model of the Southern Ocean. Eos, Trans. Amer. Geophys. Union, 72, 169174.

  • Ganachaud, A., and C. Wunsch, 2000: Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data. Nature, 408, 453457.

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

  • Getzlaff, K., C. W. Böning, and J. Deng, 2006: Lagrangian perspectives of deep water export from the subpolar North Atlantic. Geophys. Res. Lett., 33, L21S08, doi:10.1029/2006GL026470.

    • Search Google Scholar
    • Export Citation
  • Hall, M., and H. Byrden, 1982: Direct estimates and mechanisms of ocean heat transport. Deep-Sea Res., 29, 339359.

  • Holland, W., and L. Lin, 1975: On the origin of mesoscale eddies and their contribution to the general circulation of the ocean. I. A preliminary numerical experiment. J. Phys. Oceanogr., 5, 642657.

    • Search Google Scholar
    • Export Citation
  • Hughes, C., 2000: A theoretical reason to expect inviscid western boundary currents in realistic oceans. Ocean Modell., 2, 7383.

  • Hughes, C., and B. Cuevas, 2001: Why western boundary currents in realistic oceans are inviscid: A link between form stress and bottom pressure torques. J. Phys. Oceanogr., 31, 28712885.

    • Search Google Scholar
    • Export Citation
  • Jayne, S., and J. Marotzke, 2002: The oceanic eddy heat transport. J. Phys. Oceanogr., 32, 33283345.

  • Jochum, M., G. Danabasoglu, M. Holland, Y.-O. Kwon, and W. G. Large, 2008: Ocean viscosity and climate. J. Geophys. Res., 113, C06017, doi:10.1029/2007JC004515.

    • Search Google Scholar
    • Export Citation
  • Johns, W. E., T. J. Shay, J. M. Bane, and D. R. Watts, 1995: Gulf Stream structure, transport, and recirculation near 68°W. J. Geophys. Res., 100 (C1), 817838.

    • Search Google Scholar
    • Export Citation
  • Kistler, R., and Coauthors, 2001: The NCEP–NCAR 50-Year Reanalysis: Monthly means CD-ROM and documentation. Bull. Amer. Meteor. Soc., 82, 247267.

    • Search Google Scholar
    • Export Citation
  • Lavender, K., R. Davis, and W. Owens, 2000: Mid-depth recirculation observed in the interior Labrador and Irminger seas by direct velocity measurements. Nature, 407, 6668.

    • Search Google Scholar
    • Export Citation
  • Ledwell, J., E. Montgomery, K. Polzin, L. S. Laurent, R. Schmidt, and J. Toole, 2000: Evidence for enhanced mixing over rough topography in the abyssal ocean. Nature, 403, 179182.

    • 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.

  • Lozier, M., 1997: Evidence for large-scale eddy-driven gyres in the North Atlantic. Science, 277, 361364.

  • Lozier, M., 2010: Deconstructing the conveyor belt. Science, 328, 15071511.

  • Lumpkin, R., and K. Speer, 2003: Large-scale vertical and horizontal circulation in the North Atlantic Ocean. J. Phys. Oceanogr., 33, 19021920.

    • Search Google Scholar
    • Export Citation
  • McAvaney, B. J., and Coauthors, 2001: Model evaluation. Climate Change 2001: The Scientific Basis, J. T. Houghton et al., Eds., Cambridge University Press, 471–523.

    • Search Google Scholar
    • Export Citation
  • Molinari, R., R. Fine, and E. Johns, 1992: The deep western boundary current in the tropical North Atlantic. Deep-Sea Res., 39, 19671984.

    • Search Google Scholar
    • Export Citation
  • Munk, W., 1950: On the wind-driven ocean circulation. J. Meteor., 7, 7993.

  • Nakamura, M., and T. Kagimoto, 2006: Potential vorticity and eddy potential enstrophy in the North Atlantic Ocean simulated by a global eddy-resolving model. Dyn. Atmos. Oceans, 41, 2859.

    • Search Google Scholar
    • Export Citation
  • NGDC, cited 2007: National Geophysical Data Center 5-minute gridded global relief data collection. [Available online at http://www.ngdc.noaa.gov/mgg/fliers/93mgg01.html.]

  • O’Dwyer, J., and R. G. Williams, 1997: The climatological distribution of potential vorticity over the abyssal ocean. J. Phys. Oceanogr., 27, 24882506.

    • Search Google Scholar
    • Export Citation
  • Oschlies, A., 2002: Improved representation of upper-ocean dynamics and mixed layer depths in a model of the North Atlantic on switching from eddy-permitting to eddy-resolving grid resolution. J. Phys. Oceanogr., 32, 22772298.

    • Search Google Scholar
    • Export Citation
  • Pickart, R., 1992: Water mass components of the North Atlantic deep western boundary current. Deep-Sea Res., 39, 15531572.

  • Pickart, R., N. Hogg, and W. M. Smethie Jr., 2005: Determining the strength of the deep western boundary current using the chlorofluoromethane ratio. J. Phys. Oceanogr., 19, 940951.

    • Search Google Scholar
    • Export Citation
  • Polzin, K., J. Toole, H. Ledwell, and R. Schmitt, 1997: Spatial variability of turbulent mixing in the abyssal ocean. Science, 276, 9396.

    • Search Google Scholar
    • Export Citation
  • Rahmstorf, S., 2002: Ocean circulation and climate during the past 120,000 years. Nature, 419, 207214.

  • Randall, D. A., and Coauthors, 2007: Climate models and their evaluation. Climate Change 2007: The Physical Science Basis, S. Solomon et al., Eds., Cambridge University Press, 589–662.

    • Search Google Scholar
    • Export Citation
  • Rhein, M., and Coauthors, 2002: Labrador Sea Water: Pathways, CFC inventory, and formation rates. J. Phys. Oceanogr., 32, 648665.

  • Rhines, P., and W. Young, 1982: Homogenization of potential vorticity in planetary gyres. J. Fluid Mech., 122, 347367.

  • Schmitz, W., and M. McCartney, 1993: On the North Atlantic circulation. Rev. Geophys., 13, 2949.

  • Smethie, W., and R. Fine, 2001: Rates of North Atlantic Deep Water formation calculated from chlorofluorocarbon inventories. Deep-Sea Res., 48, 189215.

    • Search Google Scholar
    • Export Citation
  • Smethie, W., R. Fine, A. Putzka, and E. Jones, 2000: Tracing the flow of North Atlantic Deep Water using chlorofluorocarbons. J. Geophys. Res., 105 (C6), 14 29714 324.

    • Search Google Scholar
    • Export Citation
  • Smith, R. D., M. E. Maltrud, F. O. Bryan, and M. W. Hecht, 2000: Numerical simulation of the North Atlantic Ocean at 1/10°. J. Phys. Oceanogr., 30, 15321561.

    • Search Google Scholar
    • Export Citation
  • Spence, P., M. Eby, and A. Weaver, 2008: The sensitivity of the Atlantic meridional overturning circulation to freshwater forcing at eddy-permitting resolutions. J. Climate, 21, 26972710.

    • Search Google Scholar
    • Export Citation
  • Spence, P., O. Saenko, M. Eby, and A. Weaver, 2009: The Southern Ocean overturning: Parameterized versus permitted eddies. J. Phys. Oceanogr., 39, 16341651.

    • Search Google Scholar
    • Export Citation
  • Stammer, D., 1997: Global characteristics of ocean variability from regional TOPEX/POSEIDON altimeter measurements. J. Phys. Oceanogr., 28, 17431769.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., and A. Arons, 1960: On the abyssal circulation of the world ocean—I. Stationary planetary flow patterns on a sphere. Deep-Sea Res., 6, 140154.

    • Search Google Scholar
    • Export Citation
  • Sverdrup, H., 1947: Wind-driven currents in a baroclinic ocean; With application to the equatorial currents in the eastern Pacific. Proc. Natl. Acad. Sci. USA, 33, 318326.

    • Search Google Scholar
    • Export Citation
  • Talley, L., 2003: Shallow, intermediate, and deep overturning components of the global heat budget. J. Phys. Oceanogr., 33, 530560.

  • Talley, L., and M. McCartney, 1982: Distribution and circulation of Labrador Sea Water. J. Phys. Oceanogr., 12, 11891205.

  • Talley, L., J. Reid, and P. Robbins, 2003: Data-based meridional overturning streamfunctions for the global ocean. J. Climate, 16, 32133226.

    • Search Google Scholar
    • Export Citation
  • Treguier, A. M., S. Theetten, E. P. Chassignet, T. Penduff, R. Smith, L. Talley, J. O. Beismann, and C. Böning, 2005: The North Atlantic subpolar gyre in four high-resolution models. J. Phys. Oceanogr., 35, 757774.

    • Search Google Scholar
    • Export Citation
  • Weaver, A. J., and T. M. Hughes, 1992: Stability and variability of the thermohaline circulation and its link to climate. Trends in Physical Oceanography, Research Trends Series, Vol. 1, Council of Scientific Research Integration, 15–70.

    • Search Google Scholar
    • Export Citation
  • Weaver, A. J., and Coauthors, 2001: The UVic Earth System Climate Model: Model description, climatology, and applications to past, present and future climates. Atmos.–Ocean, 39, 361428.

    • Search Google Scholar
    • Export Citation
  • Wunsch, C., 1999: Where do ocean eddy fluxes matter? J. Geophys. Res., 104 (C6), 13 23513 249.

  • Wunsch, C., 2002: What is the thermohaline circulation? Science, 298, 11791181.

  • Wunsch, C., 2007: The past and future ocean circulation from a contemporary perspective. Ocean Circulation: Mechanisms and Impacts, Geophys. Monogr., Vol. 173, Amer. Geophys. Union, 53–74.

    • Search Google Scholar
    • Export Citation
  • Wunsch, C., and D. Roemmich, 1985: Is the North Atlantic in Sverdrup balance? J. Phys. Oceanogr., 15, 18761880.

  • Zhang, R., 2010: Latitudinal dependence of Atlantic meridional overturning circulation (AMOC) variations. Geophys. Res. Lett., 37, L16703, doi:10.1029/2010GL044474.

    • Search Google Scholar
    • Export Citation
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The Role of Bottom Pressure Torques on the Interior Pathways of North Atlantic Deep Water

Paul SpenceClimate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia

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

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Willem SijpClimate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia

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Matthew EnglandClimate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia

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Abstract

Four versions of the same global climate model, one with horizontal resolution of 1.8° × 3.6° and three with 0.2° × 0.4°, are employed to evaluate the role of ocean bottom topography and viscosity on the spatial structure of the deep circulation. This study is motivated by several recent observational studies that find that subsurface floats injected near the western boundary of the Labrador Sea most often do not continuously follow the deep western boundary current (DWBC), in contrast to the traditional view that the deep water formed in the North Atlantic predominantly follows the DWBC. It is found that, with imposed large viscosity values, the model reproduces the traditional view. However, as viscosity is reduced and the model bathymetry resolution increased, much of the North Atlantic Deep Water (NADW) separates from the western boundary and enters the low-latitude Atlantic via interior pathways distinct from the DWBC. It is shown that bottom pressure torques play an important role in maintaining these interior NADW outflows.

Corresponding author address: Paul Spence, Climate Change Research Centre, University of New South Wales, Sydney, NSW 2052, Australia. E-mail: paul.spence@unsw.edu.au

Abstract

Four versions of the same global climate model, one with horizontal resolution of 1.8° × 3.6° and three with 0.2° × 0.4°, are employed to evaluate the role of ocean bottom topography and viscosity on the spatial structure of the deep circulation. This study is motivated by several recent observational studies that find that subsurface floats injected near the western boundary of the Labrador Sea most often do not continuously follow the deep western boundary current (DWBC), in contrast to the traditional view that the deep water formed in the North Atlantic predominantly follows the DWBC. It is found that, with imposed large viscosity values, the model reproduces the traditional view. However, as viscosity is reduced and the model bathymetry resolution increased, much of the North Atlantic Deep Water (NADW) separates from the western boundary and enters the low-latitude Atlantic via interior pathways distinct from the DWBC. It is shown that bottom pressure torques play an important role in maintaining these interior NADW outflows.

Corresponding author address: Paul Spence, Climate Change Research Centre, University of New South Wales, Sydney, NSW 2052, Australia. E-mail: paul.spence@unsw.edu.au
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