• Adcroft, A., , C. Hill, , and J. Marshall, 1997: Representation of topography by shaved cells in a height coordinate ocean model. Mon. Wea. Rev., 125 , 22932315.

    • Search Google Scholar
    • Export Citation
  • Beckmann, A., , and R. Döscher, 1997: A method for improved representation of dense water spreading over topography in geopotential-coordinate models. J. Phys. Oceanogr., 27 , 581591.

    • Search Google Scholar
    • Export Citation
  • Beismann, J. O., , and R. Redler, 2003: Model simulations of CFC uptake in North Atlantic Deep Water: Effects of parameterizations and grid resolution. J. Geophys. Res., 108 .3159, doi:10.1029/2001JC0011253.

    • Search Google Scholar
    • Export Citation
  • Böning, C. W., , R. Holland, , F. Bryan, , G. Danabasoglu, , and J. C. McWilliams, 1995: An overlooked problem in model simulations of the thermohaline circulation and heat transport in the Atlantic Ocean. J. Climate, 8 , 515523.

    • Search Google Scholar
    • Export Citation
  • Bower, A. S., and Coauthors, 2002: Directly measured mid-depth circulation in the northeastern North Atlantic Ocean. Nature, 419 , 603607.

    • Search Google Scholar
    • Export Citation
  • Bryan, K., , J. K. Dukowicz, , and R. D. Smith, 1999: On the mixing coefficient in the parameterization of bolus velocity. J. Phys. Oceanogr., 29 , 24422456.

    • Search Google Scholar
    • Export Citation
  • Colin de Verdière, A., , H. Mercier, , and M. Arhan, 1989: Mesoscale variability from the western to the eastern Atlantic along 48°N. J. Phys. Oceanogr., 19 , 11491170.

    • Search Google Scholar
    • Export Citation
  • Cox, M. D., 1987: Isopycnal diffusion in a z-coordinate ocean model. Ocean Modelling, 74 , (unpublished manuscripts). 15.

  • Cuny, J., , P. B. Rhines, , P. P. Niiler, , and S. Bacon, 2002: Labrador Sea boundary currents and the fate of the Irminger Sea Water. J. Phys. Oceanogr., 32 , 627647.

    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., , and J. C. McWilliams, 1995: Sensitivity of the global ocean circulation to parameterizations of mesoscale tracer transports. J. Climate, 8 , 29672987.

    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., , J. C. McWilliams, , and P. R. Gent, 1994: The role of mesoscale tracer transports in the global ocean circulation. Science, 264 , 11231126.

    • Search Google Scholar
    • Export Citation
  • Dengg, J., , C. Böning, , U. Ernst, , R. Redler, , and A. Beckmann, 1999: Effects of an improved model representation of overflow water on the subpolar North Atlantic. International WOCE Newsletter, No. 37, WOCE International Project Office, Southampton, United Kingdom, 10–14.

  • Döscher, R., , and R. Redler, 1997: The relative importance of northern overflow and subpolar deep convection for the North Atlantic thermohaline circulation. J. Phys. Oceanogr., 27 , 18941902.

    • Search Google Scholar
    • Export Citation
  • Döscher, R., , C. W. Böning, , and P. Herrmann, 1994: Response of circulation and heat transport in the North Atlantic to changes in thermohaline forcing in northern latitudes: A model study. J. Phys. Oceanogr., 24 , 23062320.

    • Search Google Scholar
    • Export Citation
  • England, M. H., , and G. Holloway, 1998: Simulations of CFC content and water mass age in the deep North Atlantic. J. Geophys. Res., 103 , 1588515901.

    • Search Google Scholar
    • Export Citation
  • Ezer, T., , and G. L. Mellor, 2004: A generalized coordinate ocean model and a comparison of the bottom boundary layer dynamics in terrain-following and in z-level grids. Ocean Modell., 6 , 379403.

    • 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. K., , L. Talley, , and P. 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
  • Ganachaud, A., , and C. Wunsch, 2000: Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data. Nature, 408 , 453456.

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

  • Gent, P. R., , J. Willebrand, , T. McDougall, , and J. C. McWilliams, 1995: Parameterizing eddy-induced tracer transports in ocean circulation models. J. Phys. Oceanogr., 25 , 463474.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., , F. Bryan, , S. Doney, , and W. Large, 1999: A perspective on the ocean component of climate models. Exchanges, 14 , 1114.

  • Gent, P. R., , A. P. Craig, , C. M. Bitz, , and J. W. Weatherly, 2002: Parameterization improvements in an eddy-permitting ocean model for climate. J. Climate, 15 , 14471459.

    • Search Google Scholar
    • Export Citation
  • Gerdes, R., , C. Koberle, , and J. Willebrand, 1991: The influence of numerical advection schemes on the results of ocean general circulation models. Climate Dyn., 5 , 211226.

    • Search Google Scholar
    • Export Citation
  • Grey, S. M., , and K. Haines, 1999: Climatological hydrography of the North Atlantic. International WOCE Newsletter, No. 36, WOCE International Project Office, Southampton, United Kingdom, 23–25.

  • Haines, K., , and P. Wu, 1998: GCM studies of intermediate and deep waters in the Mediterranean. J. Mar. Syst., 18 , 197214.

  • Held, I. M., , and V. D. Larichev, 1996: A scaling theory for horizontally homogeneous, baroclinically unstable flow on a beta plane. J. Atmos. Sci., 53 , 946952.

    • Search Google Scholar
    • Export Citation
  • Käse, R. H., , A. Biastoch, , and D. B. Stammer, 2001: On the mid-depth circulation in the Labrador and Irminger Seas. Geophys. Res. Lett., 28 , 34333436.

    • Search Google Scholar
    • Export Citation
  • Khatiwala, S., , and M. Visbeck, 2000: An estimate of the eddy-induced circulation in the Labrador Sea. Geophys. Res. Lett., 27 , 22772280.

    • Search Google Scholar
    • Export Citation
  • Killworth, P. D., , D. Staniforth, , D. J. Webb, , and S. M. Patterson, 1991: The development of a free-surface Bryan–Cox–Semtner ocean model. J. Phys. Oceanogr., 21 , 13331348.

    • Search Google Scholar
    • Export Citation
  • Krauss, W., 1986: The North Atlantic Current. J. Geophys. Res., 91 , 50615074.

  • Lavender, K. L., , R. E. Davis, , and W. B. Owens, 2000: Mid-depth recirculation observed in the interior Labrador and Irminger Seas by direct velocity measurement. Nature, 407 , 6669.

    • Search Google Scholar
    • Export Citation
  • Lazier, J. R. N., , and D. G. Wright, 1993: Annual velocity variations in the Labrador Current. J. Phys. Oceanogr., 23 , 659678.

  • Lilly, J. M., , P. B. Rhines, , M. Visbeck, , R. Davis, , J. R. N. Lazier, , F. Schott, , and D. Farmer, 1999: Observing deep convection in the Labrador Sea during winter 1994/95. J. Phys. Oceanogr., 29 , 20652098.

    • Search Google Scholar
    • Export Citation
  • Maltrud, M. E., , and J. L. McClean, 2005: An eddy resolving global 1/10° ocean simulation. Ocean Modell., 8 , 3154.

  • Mathieu, P. P., 1998: Parameterization of mesoscale turbulence in a World Ocean model. Ph.D. thesis, Université catholique de Louvain, 203 pp. [Available from Institut d’Astronomie et de Géophysique G. Lemaitre, Univesité catholique de Louvain, Chemin du cyclotron 2, B-1348, Louvain-la-Neuve, Belgium.].

  • Mellor, G. L., , S. Hakkinen, , T. Ezer, , and R. Patchen, 2002: A generalization of a sigma coordinate ocean model and an intercomparison of model vertical grids. Ocean Forecasting: Conceptual Basis and Applications, N. Pinardi and J. Woods, Eds., Springer, 55–72 pp.

    • Search Google Scholar
    • Export Citation
  • Myers, P. G., 2002: SPOM: A regional model of the sub-polar North Atlantic. Atmos.–Ocean, 40 , 445463.

  • Myers, P. G., , and A. J. Weaver, 1995: A diagnostic barotropic finite-element ocean circulation model. J. Atmos. Oceanic Technol., 12 , 511526.

    • Search Google Scholar
    • Export Citation
  • Myers, P. G., , and D. Deacu, 2004: Labrador Sea freshwater content in a model with a partial cell topographic representation. Ocean Modell., 6 , 359377.

    • Search Google Scholar
    • Export Citation
  • NOAA, 1988: Digital relief of the surface of the earth. National Geophysical Data Center Data Announcement 88-MGG-02, National Oceanic and Atmospheric Administration, Boulder, CO.

  • NODC, 1994: World Ocean Atlas CD-ROM Series 1994. National Oceanographic Data Center, National Oceanic and Atmospheric Administration.

  • Pacanowski, R. C., , and S. M. Griffies, 1998: The MOM 3.0 manual. NOAA/Geophysical Fluid Dynamics Laboratory, Ocean Group Tech. Rep. 4, 680 pp.

  • Rahmstorf, S., 1993: A fast and complete convection scheme for ocean models. Ocean Modelling, 101 , (unpublished manuscripts). 911.

  • Redi, M. H., 1982: Oceanic isopycnic mixing by coordinate rotation. J. Phys. Oceanogr., 12 , 11541158.

  • Roberts, M. J., and Coauthors, 2004: Impact of an eddy-permitting ocean resolution on control and climate change simulations with a global coupled GCM. J. Climate, 17 , 320.

    • Search Google Scholar
    • Export Citation
  • Roberts, M. J., , and D. Marshall, 1998: Do we require adiabatic dissipation schemes in eddy-resolving ocean models? J. Phys. Oceanogr., 28 , 20502063.

    • 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
  • Stammer, D., 1998: On eddy characteristics, eddy transports, and mean flow properties. J. Phys. Oceanogr., 28 , 727739.

  • Stevens, D. P., 1991: The open boundary condition in the United Kingdom fine-resolution Antarctic model. J. Phys. Oceanogr., 21 , 14941499.

    • Search Google Scholar
    • Export Citation
  • The Lab Sea Group, 1998: The Labrador Sea deep convection experiment. Bull. Amer. Meteor. Soc., 79 , 20332058.

  • Treguier, A. M., , I. M. Held, , and V. D. Larichev, 1997: On the parameterization of quasi-geostrophic eddies in primitive equation ocean models. J. Phys. Oceanogr., 27 , 567580.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. R., , W. G. Large, , and J. G. Olson, 1990: The mean annual cycle in global ocean wind stress. J. Phys. Oceanogr., 20 , 17421760.

    • Search Google Scholar
    • Export Citation
  • Visbeck, M., , J. Marshall, , T. Haine, , and M. Spall, 1997: Specification of eddy transfer coefficients in coarse-resolution ocean models. J. Phys. Oceanogr., 27 , 381402.

    • Search Google Scholar
    • Export Citation
  • Willebrand, J., and Coauthors, 2001: Circulation characteristics in three eddy-permitting models of the North Atlantic. Progress in Oceanography., Vol. 48 , Pergamon,. 123161.

    • Search Google Scholar
    • Export Citation
  • Wright, D. K., 1997: A new eddy mixing parametrization and ocean general circulation model. International WOCE Newsletter, No. 26, WOCE International Project Office, Southampton, United Kingdom, 27–29.

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Effect of a Variable Eddy Transfer Coefficient in an Eddy-Permitting Model of the Subpolar North Atlantic Ocean

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  • 1 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
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Abstract

The effect of using a variable eddy transfer coefficient for the Gent–McWilliams (GM) parameterization in a (1/3)°-resolution ocean model of the subpolar North Atlantic Ocean is investigated. Results from four experiments with different implementations of this coefficient are compared among themselves as well as with two control experiments. A series of improvements have been obtained in all of the experiments that use a low level of explicit horizontal tracer diffusion. These include a better representation of the overflow waters originating from the Nordic seas, leading to a more realistic deep western boundary current and to increased eddy activity in the deep ocean in the eastern North Atlantic. In the same experiments, the GM velocities “help” the Labrador Sea Water to spread from the deep convection region to the currents that surround it without incurring significant spurious diapycnal mixing. Thus, two classical pathways for the spreading of this water are established. Moreover, the simulated Labrador Current and the near-surface circulation in the eastern North Atlantic are in better agreement with flow patterns inferred from observations. The increased release of available potential energy obtained in the experiments with variable eddy transfer coefficients is responsible for the simulation of a flow that varies less in time. An overly strong countercurrent still occurs in the Labrador Sea in these experiments, and it has a negative impact on the pathway of the North Atlantic Current in the “Northwest Corner” and on the hydrography of the Labrador Sea. Nonetheless and overall, the use of the variable eddy transfer coefficient has led to better representations of the general circulation and hydrography in the subpolar North Atlantic.

Corresponding author address: Daniel Deacu, Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Bldg., University of Alberta, Edmonton, AB T6G 2E3, Canada. Email: ddeacu@ualberta.ca

Abstract

The effect of using a variable eddy transfer coefficient for the Gent–McWilliams (GM) parameterization in a (1/3)°-resolution ocean model of the subpolar North Atlantic Ocean is investigated. Results from four experiments with different implementations of this coefficient are compared among themselves as well as with two control experiments. A series of improvements have been obtained in all of the experiments that use a low level of explicit horizontal tracer diffusion. These include a better representation of the overflow waters originating from the Nordic seas, leading to a more realistic deep western boundary current and to increased eddy activity in the deep ocean in the eastern North Atlantic. In the same experiments, the GM velocities “help” the Labrador Sea Water to spread from the deep convection region to the currents that surround it without incurring significant spurious diapycnal mixing. Thus, two classical pathways for the spreading of this water are established. Moreover, the simulated Labrador Current and the near-surface circulation in the eastern North Atlantic are in better agreement with flow patterns inferred from observations. The increased release of available potential energy obtained in the experiments with variable eddy transfer coefficients is responsible for the simulation of a flow that varies less in time. An overly strong countercurrent still occurs in the Labrador Sea in these experiments, and it has a negative impact on the pathway of the North Atlantic Current in the “Northwest Corner” and on the hydrography of the Labrador Sea. Nonetheless and overall, the use of the variable eddy transfer coefficient has led to better representations of the general circulation and hydrography in the subpolar North Atlantic.

Corresponding author address: Daniel Deacu, Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Bldg., University of Alberta, Edmonton, AB T6G 2E3, Canada. Email: ddeacu@ualberta.ca

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