• de Szoeke, R. A., and S. R. Springer, 2009: The materiality and neutrality of neutral density and orthobaric density. J. Phys. Oceanogr., 39, 17791799, https://doi.org/10.1175/2009JPO4042.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • de Szoeke, R. A., S. R. Springer, and D. M. Oxilia, 2000: Orthobaric density: A thermodynamic variable for ocean circulation studies. J. Phys. Oceanogr., 30, 28302852, https://doi.org/10.1175/1520-0485(2001)031<2830:>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Eden, C., and J. Willebrand, 1999: Neutral density revisited. Deep-Sea Res. II, 46, 3354, https://doi.org/10.1016/S0967-0645(98)00113-1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Forget, G., 2010: Mapping ocean observations in a dynamical framework: A 2004–06 ocean atlas. J. Phys. Oceanogr., 40, 12011221, https://doi.org/10.1175/2009JPO4043.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jackett, D. R., and T. J. McDougall, 1997: A neutral density variable for the world’s oceans. J. Phys. Oceanogr., 27, 237263, https://doi.org/10.1175/1520-0485(1997)027<0237:ANDVFT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Klocker, A., T. McDougall, and D. Jackett, 2009: A new method for forming approximately neutral surfaces. Ocean Sci., 5, 155172, https://doi.org/10.5194/os-5-155-2009.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Levitus, S., 1982: Climatological Atlas of the World Ocean. NOAA Prof. Paper 13, 173 pp. and 17 microfiche.

  • MacKinnon, J., L. St Laurent, and A. C. N. Garabato, 2013: Diapycnal mixing processes in the ocean interior. Ocean Circulation and Climate, International Geophysics Series, Vol. 103, Elsevier, 159–183.

    • Crossref
    • Export Citation
  • McDougall, T. J., 1987a: Neutral surfaces. J. Phys. Oceanogr., 17, 19501964, https://doi.org/10.1175/1520-0485(1987)017<1950:NS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., 1987b: The vertical motion of submesoscale coherent vortices across neutral surfaces. J. Phys. Oceanogr., 17, 23342342, https://doi.org/10.1175/1520-0485(1987)017<2334:TVMOSC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., 2003: Potential enthalpy: A conservative oceanic variable for evaluating heat content and heat fluxes. J. Phys. Oceanogr., 33, 945963, https://doi.org/10.1175/1520-0485(2003)033<0945:PEACOV>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and D. R. Jackett, 1988: On the helical nature of neutral trajectories in the ocean. Prog. Oceanogr., 20, 153183, https://doi.org/10.1016/0079-6611(88)90001-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and D. R. Jackett, 2005a: An assessment of orthobaric density in the global ocean. J. Phys. Oceanogr., 35, 20542075, https://doi.org/10.1175/JPO2796.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and D. R. Jackett, 2005b: The material derivative of neutral density. J. Mar. Res., 63, 159185, https://doi.org/10.1357/0022240053693734.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and D. R. Jackett, 2007: The thinness of the ocean in S–Θ–p space and the implications for mean diapycnal advection. J. Phys. Oceanogr., 37, 17141732, https://doi.org/10.1175/JPO3114.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., S. Groeskamp, and S. M. Griffies, 2014: On geometrical aspects of interior ocean mixing. J. Phys. Oceanogr., 44, 21642175, https://doi.org/10.1175/JPO-D-13-0270.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., S. Groeskamp, and S. Griffies, 2017: Comment on Tailleux, R. Neutrality versus materiality: A thermodynamic theory of neutral surfaces. Fluids 2016, 1, 32. Fluids, 2, 19, https://doi.org/10.3390/fluids2020019.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDowell, S. E., and H. T. Rossby, 1978: Mediterranean water: An intense mesoscale eddy off the Bahamas. Science, 202, 10851087, https://doi.org/10.1126/science.202.4372.1085.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McWilliams, J. C., 1985: Submesoscale, coherent vortices in the ocean. Rev. Geophys., 23, 165182, https://doi.org/10.1029/RG023i002p00165.

  • Menemenlis, D., and Coauthors, 2005: NASA supercomputer improves prospects for ocean climate research. Eos, Trans. Amer. Geophys. Union, 86, 8996, https://doi.org/10.1029/2005EO090002.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Montgomery, R. B., 1937: A suggested method for representing gradient flow in isentropic surfaces. Bull. Amer. Meteor. Soc., 18, 210212, https://doi.org/10.1175/1520-0477-18.6-7.210.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nash, J. E., and J. V. Sutcliffe, 1970: River flow forecasting through conceptual models part I—A discussion of principles. J. Hydrol., 10, 282290, https://doi.org/10.1016/0022-1694(70)90255-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nycander, J., M. Hieronymus, and F. Roquet, 2015: The nonlinear equation of state of sea water and the global water mass distribution. Geophys. Res. Lett., 42, 77147721, https://doi.org/10.1002/2015GL065525.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Reid, J. L., and R. J. Lynn, 1971: On the influence of the Norwegian-Greenland and Weddell seas upon the bottom waters of the Indian and Pacific oceans. Deep-Sea Res. Oceanogr. Abstr., 18, 10631088, https://doi.org/10.1016/0011-7471(71)90094-5.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stanley, G. J., 2019a: Neutral surface topology. Ocean Modell., 138, 88106, https://doi.org/10.1016/j.ocemod.2019.01.008.

  • Stanley, G. J., 2019b: The exact geostrophic streamfunction for neutral surfaces. Ocean Modell., 138, 107121, https://doi.org/10.1016/j.ocemod.2019.04.002.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tailleux, R., 2013: Available potential energy density for a multicomponent Boussinesq fluid with arbitrary nonlinear equation of state. J. Fluid Mech., 735, 499518, https://doi.org/10.1017/jfm.2013.509.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tailleux, R., 2016: Generalized patched potential density and thermodynamic neutral density: Two new physically based quasi-neutral density variables for ocean water masses analyses and circulation studies. J. Phys. Oceanogr., 46, 35713584, https://doi.org/10.1175/JPO-D-16-0072.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wüst, G. 1933: Das Bodenwasser und die Gliederung der atlantischen Tiefsee: de Gruyter.

  • Young, W. R., 2010: Dynamic enthalpy, conservative temperature, and the seawater Boussinesq approximation. J. Phys. Oceanogr., 40, 394400, https://doi.org/10.1175/2009JPO4294.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
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A Pressure-Invariant Neutral Density Variable for the World's Oceans

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  • 1 School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales, Australia
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Abstract

We present a new method to calculate the neutral density of an arbitrary water parcel. Using this method, the value of neutral density depends only on the parcel’s salinity, temperature, latitude, and longitude and is independent of the pressure (or depth) of the parcel, and is therefore independent of heave in observations or high-resolution models. In this method we move the parcel adiabatically and isentropically like a submesoscale coherent vortex (SCV) to its level of neutral buoyancy on four nearby water columns of a climatological atlas. The parcel’s neutral density γSCV is interpolated from prelabeled neutral density values at these four reference locations in the climatological atlas. This method is similar to the neutral density variable γn of Jackett and McDougall: their discretization of the neutral relationship equated the potential density of two parcels referenced to their average pressure, whereas our discretization equates the parcels’ potential density referenced to the pressure of the climatological parcel. We calculate the numerical differences between γSCV and γn, and we find similar variations of γn and γSCV on the ω surfaces of Klocker, McDougall, and Jackett. We also find that isosurfaces of γn and γSCV deviate from the neutral tangent plane by similar amounts. We compare the material derivative of γSCV with that of γn, finding their total material derivatives are of a similar magnitude.

© 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Yandong Lang, yandonglang@student.unsw.edu.au

Abstract

We present a new method to calculate the neutral density of an arbitrary water parcel. Using this method, the value of neutral density depends only on the parcel’s salinity, temperature, latitude, and longitude and is independent of the pressure (or depth) of the parcel, and is therefore independent of heave in observations or high-resolution models. In this method we move the parcel adiabatically and isentropically like a submesoscale coherent vortex (SCV) to its level of neutral buoyancy on four nearby water columns of a climatological atlas. The parcel’s neutral density γSCV is interpolated from prelabeled neutral density values at these four reference locations in the climatological atlas. This method is similar to the neutral density variable γn of Jackett and McDougall: their discretization of the neutral relationship equated the potential density of two parcels referenced to their average pressure, whereas our discretization equates the parcels’ potential density referenced to the pressure of the climatological parcel. We calculate the numerical differences between γSCV and γn, and we find similar variations of γn and γSCV on the ω surfaces of Klocker, McDougall, and Jackett. We also find that isosurfaces of γn and γSCV deviate from the neutral tangent plane by similar amounts. We compare the material derivative of γSCV with that of γn, finding their total material derivatives are of a similar magnitude.

© 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Yandong Lang, yandonglang@student.unsw.edu.au
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