Editorial Type:
Article
Article Type:
Research Article

Double Diffusion in Saline Powell Lake, British Columbia

Benjamin Scheifele Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada

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Rich Pawlowicz Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada

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Tobias Sommer Surface Waters Research and Management, Eawag, Kastanienbaum, and Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland

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Alfred Wüest Surface Waters Research and Management, Eawag, Kastanienbaum, and Margaretha Kamprad Chair, Physics of Aquatic Systems Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

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Print Publication:
01 Nov 2014
DOI:
https://doi.org/10.1175/JPO-D-14-0070.1
Page(s):
2893–2908
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Abstract

Powell Lake contains a deep layer of relic seawater separated from the ocean since the last ice age. Permanently stratified and geothermally heated from below, this deep layer is an isolated geophysical domain suitable for studying double-diffusive convection. High-resolution CTD and microstructure measurements show several double-diffusive staircases (Rρ = 1.6 to 6) in the deep water, separated vertically by smooth high-gradient regions with much larger density ratios. The lowest staircase contains steps that are laterally coherent on the basin scale and have a well-defined vertical structure. On average, temperature steps in this staircase are 4 mK, salinity steps are 2 mg kg−1, and mixed layer heights are 70 cm. The CTD is capable of measuring bulk characteristics of the staircase in both temperature and salinity. Microstructure measurements are limited to temperature alone, but resolve the maximum temperature gradients in the center of selected laminar interfaces. Two different algorithms for characterizing the staircase are compared. Consistent estimates of the steady-state heat flux (27 mW m−2) are obtained from measurements above and below the staircase, as well as from microstructure measurements in the center of smooth interfaces. Estimates obtained from bulk interface gradients underestimate the steady-state flux by nearly a factor of 2. The mean flux calculated using a standard 4/3 flux law parameterization agrees well with the independent estimates, but inconsistencies between the parameterization and the observations remain. These inconsistencies are examined by comparing the underlying scaling relationship to the measurements.

Corresponding author address: Benjamin Scheifele, Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver BC V6T 1Z4, Canada. E-mail: bscheife@eos.ubc.ca

Abstract

Powell Lake contains a deep layer of relic seawater separated from the ocean since the last ice age. Permanently stratified and geothermally heated from below, this deep layer is an isolated geophysical domain suitable for studying double-diffusive convection. High-resolution CTD and microstructure measurements show several double-diffusive staircases (Rρ = 1.6 to 6) in the deep water, separated vertically by smooth high-gradient regions with much larger density ratios. The lowest staircase contains steps that are laterally coherent on the basin scale and have a well-defined vertical structure. On average, temperature steps in this staircase are 4 mK, salinity steps are 2 mg kg−1, and mixed layer heights are 70 cm. The CTD is capable of measuring bulk characteristics of the staircase in both temperature and salinity. Microstructure measurements are limited to temperature alone, but resolve the maximum temperature gradients in the center of selected laminar interfaces. Two different algorithms for characterizing the staircase are compared. Consistent estimates of the steady-state heat flux (27 mW m−2) are obtained from measurements above and below the staircase, as well as from microstructure measurements in the center of smooth interfaces. Estimates obtained from bulk interface gradients underestimate the steady-state flux by nearly a factor of 2. The mean flux calculated using a standard 4/3 flux law parameterization agrees well with the independent estimates, but inconsistencies between the parameterization and the observations remain. These inconsistencies are examined by comparing the underlying scaling relationship to the measurements.

Corresponding author address: Benjamin Scheifele, Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver BC V6T 1Z4, Canada. E-mail: bscheife@eos.ubc.ca
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  • Caldwell, D. R., 1974: Thermal conductivity of sea water. Deep-Sea Res. Oceanogr. Abstr.,21, 131–137, doi:10.1016/0011-7471(74)90070-9.

    • Search Google Scholar
    • Export Citation

  • Carmack, E., W. Williams, S. Zimmermann, and F. McLaughlin, 2012: The Arctic Ocean warms from below. Geophys. Res. Lett.,39, L07604, doi:10.1029/2012GL050890.

  • Carpenter, J. R., and M.-L. Timmermans, 2014: Does rotation influence double-diffusive fluxes in polar oceans? J. Phys. Oceanogr., 44, 289–296, doi:10.1175/JPO-D-13-098.1.

    • Search Google Scholar
    • Export Citation

  • Carpenter, J. R., T. Sommer, and A. Wüest, 2012: Simulations of a double-diffusive interface in the diffusive convection regime. J. Fluid Mech., 711, 411–436, doi:10.1017/jfm.2012.399.

    • Search Google Scholar
    • Export Citation

  • Cleveland, W. S., 1993: Visualizing Data. Hobart Press, 360 pp.

  • Crapper, P. F., 1975: Measurements across a diffusive interface. Deep-Sea Res. Oceanogr. Abstr.,22, 537–545, doi:10.1016/0011-7471(75)90034-0.

    • Search Google Scholar
    • Export Citation

  • Flanagan, J. D., A. S. Lefler, and T. Radko, 2013: Heat transport through diffusive interfaces. Geophys. Res. Lett., 40, 2466–2470, doi:10.1002/grl.50440.

    • Search Google Scholar
    • Export Citation

  • Hoare, R., 1968: Thermohaline convection in Lake Vanda, Antarctica. J. Geophys. Res., 73, 607–612, doi:10.1029/JB073i002p00607.

  • Horne, R. A., and D. S. Johnson, 1966: The viscosity of compressed seawater. J. Geophys. Res., 71, 5275–5277, doi:10.1029/JZ071i022p05275.

    • Search Google Scholar
    • Export Citation

  • Huppert, H. E., 1971: On the stability of a series of double-diffusive layers. Deep-Sea Res. Oceanogr. Abstr.,18, 1005–1021, doi:10.1016/0011-7471(71)90005-2.

    • Search Google Scholar
    • Export Citation

  • Hyndman, R. D., 1976: Heat flow measurements in the inlets of southwestern British Columbia. J. Geophys. Res., 81, 337–349, doi:10.1029/JB081i002p00337.

    • Search Google Scholar
    • Export Citation

  • IOC, SCOR, and IAPSO, 2010: The International Thermodynamic Equation of Seawater—2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides 56, 220 pp. [Available online at http://www.teos-10.org/pubs/TEOS-10_Manual.pdf.]

  • Kelley, D. E., 1990: Fluxes through diffusive staircases: A new formulation. J. Geophys. Res., 95, 3365–3371, doi:10.1029/JC095iC03p03365.

    • Search Google Scholar
    • Export Citation

  • Kelley, D. E., H. J. S. Fernando, A. E. Gargett, J. Tanny, and E. Özsoy, 2003: The diffusive regime of double-diffusive convection. Prog. Oceanogr., 56, 461–468, doi:10.1016/S0079-6611(03)00026-0.

    • Search Google Scholar
    • Export Citation

  • Linden, P. F., and T. G. L. Shirtcliffe, 1978: The diffusive interface in double-diffusive convection. J. Fluid Mech., 87, 417–432, doi:10.1017/S002211207800169X.

    • Search Google Scholar
    • Export Citation

  • Marmorino, G. O., and D. R. Caldwell, 1976: Heat and salt transport through a diffusive thermohaline interface. Deep-Sea Res. Oceanogr. Abstr.,23, 59–67, doi:10.1016/0011-7471(76)90808-1.

    • Search Google Scholar
    • Export Citation

  • Mathews, W. H., 1962: Bathymetry of Powell Lake, British Columbia. Institute of Oceanography, University of British Columbia, Tech. Rep. 13, 7 pp.

  • Mathews, W. H., J. G. Fyles, and H. W. Nasmith, 1970: Postglacial crustal movements in southwestern British Columbia and adjacent Washington State. Can. J. Earth Sci., 7, 690–702, doi:10.1139/e70-068.

    • Search Google Scholar
    • Export Citation

  • McDougall, T. J., 1983: Greenland Sea Bottom Water formation: A balance between advection and double-diffusion. Deep-Sea Res.,30A, 1109–1117, doi:10.1016/0198-0149(83)90090-0.

    • Search Google Scholar
    • Export Citation

  • Newell, T. A., 1984: Characteristics of a double-diffusive interface at high density stability ratios. J. Fluid Mech., 149, 385–401, doi:10.1017/S0022112084002718.

    • Search Google Scholar
    • Export Citation

  • Newman, F. C., 1976: Temperature steps in Lake Kivu: A bottom heated saline lake. J. Phys. Oceanogr., 6, 157–163, doi:10.1175/1520-0485(1976)006<0157:TSILKA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Noguchi, T., and H. Niino, 2010a: Multi-layered diffusive convection. Part 1. Spontaneous layer formation. J. Fluid Mech., 651, 443–464, doi:10.1017/S0022112009994150.

    • Search Google Scholar
    • Export Citation

  • Noguchi, T., and H. Niino, 2010b: Multi-layered diffusive convection. Part 2. Dynamics of layer evolution. J. Fluid Mech., 651, 465–481, doi:10.1017/S0022112010994160.

    • Search Google Scholar
    • Export Citation

  • Osborn, T. R., 1973: Temperature microstructure in Powell Lake. J. Phys. Oceanogr., 3, 302–307, doi:10.1175/1520-0485(1973)003<0302:TMIPL>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Özsoy, E., and Ü. Ünlüata, 1997: Oceanography of the Black Sea: A review of some recent results. Earth-Sci. Rev., 42, 231–272, doi:10.1016/S0012-8252(97)81859-4.

    • Search Google Scholar
    • Export Citation

  • Özsoy, E., Ü. Ünlüata, and Z. Top, 1993: The evolution of Mediterranean water in the Black Sea: Interior mixing and material transport by double diffusive intrusions. Prog. Oceanogr., 31, 275–320, doi:10.1016/0079-6611(93)90004-W.

    • Search Google Scholar
    • Export Citation

  • Padman, L., and T. M. Dillon, 1987: Vertical heat fluxes through the Beaufort Sea thermohaline staircase. J. Geophys. Res., 92, 10 799–10 806, doi:10.1029/JC092iC10p10799.

    • Search Google Scholar
    • Export Citation

  • Padman, L., and T. M. Dillon, 1989: Thermal microstructure and internal waves in the Canada basin diffusive staircase. Deep-Sea Res.,36A, 531–542, doi:10.1016/0198-0149(89)90004-6.

    • Search Google Scholar
    • Export Citation

  • Polyakov, I., A. Pnyushkov, R. Rember, V. Ivanov, Y. Lenn, L. Padman, and E. Carmack, 2012: Mooring-based observations of double-diffusive staircases over the Laptev Sea slope. J. Phys. Oceanogr., 42, 95–109, doi:10.1175/2011JPO4606.1.

    • Search Google Scholar
    • Export Citation

  • Radko, T., 2003: A mechanism for layer formation in a double-diffusive fluid. J. Fluid Mech., 497, 365–380, doi:10.1017/S0022112003006785.

    • Search Google Scholar
    • Export Citation

  • Radko, T., 2013: Double-Diffusive Convection. Cambridge University Press, 342 pp.

  • Radko, T., J. D. Flanagan, S. Stellmach, and M.-L. Timmermans, 2014: Double-diffusive recipes. Part II: Layer-merging events. J. Phys. Oceanogr., 44, 1285–1305, doi:10.1175/JPO-D-13-0156.1.

    • Search Google Scholar
    • Export Citation

  • Sanderson, B., K. Perry, and T. Pedersen, 1986: Vertical diffusion in meromictic Powell Lake, British Columbia. J. Geophys. Res., 91, 7647–7655, doi:10.1029/JC091iC06p07647.

    • Search Google Scholar
    • Export Citation

  • Schmid, M., A. Lorke, C. Dinkel, G. Tanyileke, and A. Wüest, 2004: Double-diffusive convection in Lake Nyos, Cameroon. Deep-Sea Res. I, 51, 1097–1111, doi:10.1016/j.dsr.2004.02.010.

    • Search Google Scholar
    • Export Citation

  • Schmid, M., M. Busbridge, and A. Wüest, 2010: Double-diffusive convection in Lake Kivu. Limnol. Oceanogr., 55, 225–238, doi:10.4319/lo.2010.55.1.0225.

    • Search Google Scholar
    • Export Citation

  • Sharqawy, M. H., J. H. Lienhard, and S. M. Zubair, 2010: Thermophysical properties of seawater: A review of existing correlations and data. Desalin. Water Treat., 16, 354–380, doi:10.5004/dwt.2010.1079.

    • Search Google Scholar
    • Export Citation

  • Sirevaag, A., and I. Fer, 2012: Vertical heat transfer in the Arctic Ocean: The role of double-diffusive mixing. J. Geophys. Res.,117, C07010, doi:10.1029/2012JC007910.

  • Sommer, T., J. R. Carpenter, M. Schmid, R. G. Lueck, M. Schurter, and A. Wüest, 2013a: Interface structure and flux laws in a natural double-diffusive layering. J. Geophys. Res. Oceans, 118, 6092–6106, doi:10.1002/2013JC009166.

    • Search Google Scholar
    • Export Citation

  • Sommer, T., J. R. Carpenter, M. Schmid, R. G. Lueck, and A. Wüest, 2013b: Revisiting microstructure sensor responses with implications for double-diffusive fluxes. J. Atmos. Oceanic Technol., 30, 1907–1923, doi:10.1175/JTECH-D-12-00272.1.

    • Search Google Scholar
    • Export Citation

  • Timmermans, M.-L., C. Garrett, and E. Carmack, 2003: The thermohaline structure and evolution of the deep waters in the Canada basin, Arctic Ocean. Deep-Sea Res. I, 50, 1305–1321, doi:10.1016/S0967-0637(03)00125-0.

    • Search Google Scholar
    • Export Citation

  • Timmermans, M.-L., J. Toole, R. Krishfield, and P. Winsor, 2008: Ice-tethered profiler observations of the double-diffusive staircase in the Canada basin thermocline. J. Geophys. Res., 113, C00A02, doi:10.1029/2008JC004829.

    • Search Google Scholar
    • Export Citation

  • Turner, J. S., 1965: The coupled turbulent transports of salt and heat across a sharp density interface. Int. J. Heat Mass Transfer, 8, 759–767, doi:10.1016/0017-9310(65)90022-0.

    • Search Google Scholar
    • Export Citation

  • Turner, J. S., 1968: The behaviour of a stable salinity gradient heated from below. J. Fluid Mech., 33, 183–200, doi:10.1017/S0022112068002442.

    • Search Google Scholar
    • Export Citation

  • Turner, J. S., 1973: Buoyancy Effects in Fluids. Cambridge University Press, 367 pp.

  • Williams, P. M., W. H. Mathews, and G. L. Pickard, 1961: A lake in British Columbia containing old sea-water. Nature, 191, 830–832, doi:10.1038/191830b0.

    • Search Google Scholar
    • Export Citation

  • Wüest, A., T. Sommer, M. Schmid, and J. Carpenter, 2012: Diffusive-type of double diffusion in lakes—A review. Environmental Fluid Mechanics: Memorial Volume in Honour of the Late Professor Gerhard H. Jirka, W. Rodi and M. Uhlmann, Eds., CRC Press, 271–284.

  • Zhou, S.-Q., and Y.-Z. Lu, 2013: Characterization of double diffusive convection steps and heat budget in the deep Arctic Ocean. J. Geophys. Res. Oceans, 118, 6672–6686, doi:10.1002/2013JC009141.

    • Search Google Scholar
    • Export Citation
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