• Borowski, D., R. Gerdes, and D. Olbers, 2002: Thermohaline and wind forcing of a circumpolar channel with blocked geostrophic contours. J. Phys. Oceanogr., 32, 25202540.

    • Search Google Scholar
    • Export Citation
  • Clark, P. U., N. G. Pisias, T. F. Stocker, and A. J. Weaver, 2002: The role of the thermohaline circulation in abrupt climate change. Nature, 415, 863869.

    • Search Google Scholar
    • Export Citation
  • Gayen, B., R. W. Griffiths, G. O. Hughes, and J. A. Saenz, 2013: Energetics of horizontal convection. J. Fluid Mech.,716, R10, doi:10.1017/jfm.2012.592.

  • Hawkins, E., R. S. Smith, L. C. Allison, J. M. Gregory, T. J. Woollings, H. Pohlmann, and B. De Cuevas, 2011: Bistability of the Atlantic overturning circulation in a global climate model and links to ocean freshwater transport. Geophys. Res. Lett.,38, L10605, doi:10.1029/2011GL047208.

  • Hogg, A. M., 2010: An Antarctic Circumpolar Current driven by surface buoyancy forcing. Geophys. Res. Lett., 37, L23601, doi:10.1029/2010GL044777.

    • Search Google Scholar
    • Export Citation
  • Holliday, D., and M. E. McIntyre, 1981: On potential energy density in an incompressible, stratified fluid. J. Fluid Mech., 107, 221225, doi:10.1017/S0022112081001742.

    • Search Google Scholar
    • Export Citation
  • Hughes, C. W., and C. Wilson, 2008: Wind work on the geostrophic ocean circulation: An observational study of the effect of small scales in the wind stress. J. Geophys. Res., 113, C02016, doi:10.1029/2007JC004371.

    • Search Google Scholar
    • Export Citation
  • Hughes, G. O., and R. W. Griffiths, 2008: Horizontal convection. Annu. Rev. Fluid Mech., 40, 185208, doi:10.1146/annurev.fluid.40.111406.102148.

    • Search Google Scholar
    • Export Citation
  • Hughes, G. O., A. M. Hogg, and R. W. Griffiths, 2009: Available potential energy and irreversible mixing in the meridional overturning circulation. J. Phys. Oceanogr., 39, 31303146.

    • Search Google Scholar
    • Export Citation
  • Huisman, S. E., M. den Toom, H. A. Dijkstra, and S. Drijfhout, 2010: An indicator of the multiple equilibria regime of the Atlantic meridional overturning circulation. J. Phys. Oceanogr., 40, 551567.

    • Search Google Scholar
    • Export Citation
  • Huisman, S. E., H. A. Dijkstra, A. S. von der Heydt, and W. P. M. de Ruijter, 2012: Does net EP set a preference for North Atlantic sinking? J. Phys. Oceanogr., 42, 1781–1792.

    • Search Google Scholar
    • Export Citation
  • Jones, D. C., T. Ito, and N. S. Lovenduski, 2011: The transient response of the Southern Ocean pycnocline to changing atmospheric winds. Geophys. Res. Lett., 38, L15604, doi:10.1029/2011GL048145.

    • Search Google Scholar
    • Export Citation
  • Kuhlbrodt, T., A. Griesel, M. Montoya, A. Levermann, M. Hofmann, and S. Rahmstorf, 2007: On the driving processes of the Atlantic meridional overturning circulation. Rev. Geophys.,45, RG2001, doi:10.1029/2004RG000166.

  • Marsh, R., D. Desbruyères, J. L. Bamber, B. A. de Cuevas, A. C. Coward, and Y. Aksenov, 2010: Short-term impacts of enhanced Greenland freshwater fluxes in an eddy-permitting ocean model. Ocean Sci., 6, 749760, doi:10.5194/os-6-749-2010.

    • Search Google Scholar
    • Export Citation
  • Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey, 1997: A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers. J. Geophys. Res., 102 (C3), 57535766.

    • Search Google Scholar
    • Export Citation
  • Molemaker, M. J., and J. C. McWilliams, 2010: Local balance and cross-scale flux of available potential energy. J. Fluid Mech., 645, 295–314, doi:10.1017/S0022112009992643.

    • Search Google Scholar
    • Export Citation
  • Morrison, A. K., A. M. Hogg, and M. L. Ward, 2011: Sensitivity of the Southern Ocean overturning circulation to surface buoyancy forcing. Geophys. Res. Lett., 38, L14602, doi:10.1029/2011GL048031.

    • Search Google Scholar
    • Export Citation
  • Munday, D. R., H. L. Johnson, and D. P. Marshall, 2013: Eddy saturation of equilibrated circumpolar currents. J. Phys. Oceanogr., 43, 507–532.

    • Search Google Scholar
    • Export Citation
  • Munk, W., and C. Wunsch, 1998: Abyssal recipes II: Energetics of tidal and wind mixing. Deep-Sea Res., 45, 19762009.

  • Paparella, F., and W. R. Young, 2002: Horizontal convection is non-turbulent. J. Fluid Mech., 466, 205214.

  • Rahmstorf, S., 1995: Bifurcations of the Atlantic thermohaline circulation in response to changes in the hydrological cycle. Nature, 378, 145149.

    • Search Google Scholar
    • Export Citation
  • Roullet, G., and P. Klein, 2009: Available potential energy diagnosis in a direct numerical simulation of rotating stratified turbulence. J. Fluid Mech., 624, 45–55, doi:10.1017/S0022112008004473.

    • Search Google Scholar
    • Export Citation
  • Saenko, O. A., 2013: Energetics of weakening and recovery of the Atlantic overturning in a climate change simulation. Geophys. Res. Lett.,40, 888–892, doi:10.1002/grl.50101.

  • Saenz, J. A., A. M. Hogg, G. O. Hughes, and R. W. Griffiths, 2012: Mechanical power input from buoyancy and wind to the circulation in an ocean model. Geophys. Res. Lett.,39, L13605, doi:10.1029/2012GL052035.

  • Scotti, A., and B. White, 2011: Is horizontal convection really “non-turbulent?” Geophys. Res. Lett.,38, L21609, doi:10.1029/2011GL049701.

  • Shakespeare, C. J., and A. M. Hogg, 2012: An analytical model of the response of the meridional overturning circulation to changes in wind and buoyancy forcing. J. Phys. Oceanogr., 42, 1270–1287.

    • Search Google Scholar
    • Export Citation
  • Smith, R. S., and J. M. Gregory, 2009: A study of the sensitivity of ocean overturning circulation and climate to freshwater input in different regions of the North Atlantic. Geophys. Res. Lett.,36, L15701, doi:10.1029/2009GL038607.

  • Stommel, H., 1961: Thermohaline convection with two stable regimes of flow. Tellus, 13, 224230.

  • Stouffer, R. J., and Coauthors, 2006: Investigating the causes of the response of the thermohaline circulation to past and future climate changes. J. Climate,19, 1365–1387.

  • Tailleux, R., 2009: On the energetics of stratified turbulent mixing, irreversible thermodynamics, Boussinesq models and the ocean heat engine controversy. J. Fluid Mech., 638, 339–382, doi:10.1017/S002211200999111X.

    • Search Google Scholar
    • Export Citation
  • Toggweiler, J. R., and B. Samuels, 1998: On the ocean's large-scale circulation near the limit of no vertical mixing. J. Phys. Oceanogr., 28, 18321852.

    • Search Google Scholar
    • Export Citation
  • Weijer, W., M. E. Maltrud, M. W. Hecht, H. A. Dijkstra, and M. A. Kliphuis, 2012: Response of the Atlantic Ocean circulation to Greenland Ice Sheet melting in a strongly-eddying ocean model. Geophys. Res. Lett.,39, L09606, doi:10.1029/2012GL051611.

  • Winters, K. B., and R. Barkan, 2012: Available potential energy density for Boussinesq fluid flow. J. Fluid Mech., 714, 476–488.

  • Winters, K. B., P. N. Lombard, J. J. Riley, and E. A. D'Asaro, 1995: Available potential energy and mixing in density-stratified fluids. J. Fluid Mech., 289, 115128.

    • Search Google Scholar
    • Export Citation
  • Wolfe, C. L., and P. Cessi, 2011: The adiabatic pole-to-pole overturning circulation. J. Phys. Oceanogr., 41, 17951810.

  • Wunsch, C., and R. Ferrari, 2004: Vertical mixing, energy, and the general circulation of the oceans. Annu. Rev. Fluid Mech., 36, 281314.

    • Search Google Scholar
    • Export Citation
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The Energetics of a Collapsing Meridional Overturning Circulation

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  • 1 Research School of Earth Sciences, and ARC Centre of Excellence for Climate System Science, The Australian National University, Canberra, Australian Capital Territory, Australia
  • | 2 Institute for Marine and Atmospheric Research, Department of Physics and Astronomy, Utrecht University, Utrecht, Netherlands
  • | 3 Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
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Abstract

A well-studied example of natural climate variability is the impact of large freshwater input to the polar oceans, simulating glacial melt release or an amplification of the hydrological cycle. Such forcing can reduce, or entirely eliminate, the formation of deep water in the polar latitudes and thereby weaken the Atlantic meridional overturning circulation (MOC). This study uses a series of idealized, eddy-permitting numerical simulations to analyze the energetic constraints on the Atlantic Ocean's response to anomalous freshwater forcing. In this model, the changes in MOC are not correlated with the global input of mechanical energy: both kinetic energy and available potential energy (APE) increase with northern freshwater forcing, while the MOC decreases. However, a regional analysis of APE density supports the notion that local maxima in APE density control the response of the MOC to freshwater forcing perturbations. A coupling between APE input and changes in local density anomalies accounts for the difference in time scales between the recovery and collapse of the MOC.

Corresponding author address: Andrew Hogg, Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia. E-mail: Andy.Hogg@anu.edu.au

Abstract

A well-studied example of natural climate variability is the impact of large freshwater input to the polar oceans, simulating glacial melt release or an amplification of the hydrological cycle. Such forcing can reduce, or entirely eliminate, the formation of deep water in the polar latitudes and thereby weaken the Atlantic meridional overturning circulation (MOC). This study uses a series of idealized, eddy-permitting numerical simulations to analyze the energetic constraints on the Atlantic Ocean's response to anomalous freshwater forcing. In this model, the changes in MOC are not correlated with the global input of mechanical energy: both kinetic energy and available potential energy (APE) increase with northern freshwater forcing, while the MOC decreases. However, a regional analysis of APE density supports the notion that local maxima in APE density control the response of the MOC to freshwater forcing perturbations. A coupling between APE input and changes in local density anomalies accounts for the difference in time scales between the recovery and collapse of the MOC.

Corresponding author address: Andrew Hogg, Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia. E-mail: Andy.Hogg@anu.edu.au
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