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Double Diffusion in Saline Powell Lake, British Columbia

机译：不列颠哥伦比亚省盐湖鲍威尔湖的双重扩散

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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 (R_ρ = 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 (27mWm~(-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.
机译：自上次冰河时代以来，鲍威尔湖（Powell Lake）就有一层深层的遗迹海水与海洋分离。该深层是永久分层的，并从下方进行地热加热，是一个孤立的地球物理区域，适合研究双扩散对流。高分辨率CTD和微观结构测量显示，深水中有多个双扩散阶梯（R_ρ= 1.6至6），垂直阶梯由光滑的高梯度区域以较大的密度比垂直分隔。最低的楼梯包含台阶，这些台阶在流域尺度上横向一致，并具有明确的垂直结构。该楼梯的平均温度阶梯为4 mK，盐度阶梯为2 mg kg〜（-1），混合层高度为70 cm。 CTD能够测量温度和盐度下楼梯的整体特征。显微组织的测量仅限于温度，但可以解决所选层流界面中心的最大温度梯度。比较了两种用于表征楼梯的不同算法。稳态热通量（27mWm〜（-2））的一致估计是从阶梯上方和下方的测量以及光滑界面中心的微观结构测量得出的。从体界面梯度获得的估计值将稳态通量低估了将近2倍。使用标准4/3通量定律参数化计算的平均通量与独立估计值非常吻合，但是参数化和观测值之间仍然存在不一致之处。通过将基础缩放关系与测量结果进行比较，可以检查这些不一致之处。

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  • 来源
    《Journal of Physical Oceanography》 |2014年第11期|2893-2908|共16页
  • 作者

    Benjamin Scheifele; Rich Pawlowicz; Tobias Sommer; Alfred Wueest;

  • 作者单位

    Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver BC V6T 1Z4, Canada;

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

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

    Surface Waters Research and Management, Eawag, Kastanienbaum, and Margaretha Kamprad , Physics of Aquatic Systems Laboratory, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland;

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