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首页> 外文期刊>Journal of Physical Oceanography >Dynamic and Double-Diffusive Instabilities in a Weak Pycnocline. Part Ⅰ: Observations of Heat Flux and Diffusivity in the Vicinity of Maud Rise, Weddell Sea
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Dynamic and Double-Diffusive Instabilities in a Weak Pycnocline. Part Ⅰ: Observations of Heat Flux and Diffusivity in the Vicinity of Maud Rise, Weddell Sea

机译：弱碧萝oc中的动态和双扩散不稳定性。第一部分：韦德海莫德上升附近热通量和扩散率的观测

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摘要

An expedition to study the stability of the weakly stratified water column in the eastern Weddell Sea was undertaken in the austral winter of 2005. A regional CTD survey around Maud Rise delineated water mass boundaries associated with flow around the seamount and identified areas most susceptible to overturning. A downstream region of the seamount Taylor column was found least stable, with a potential density difference across the pycnocline less than 0.018 kg m~(-3). Intensive water column measurements, including 1300 profiles of temperature, conductivity, and fast-response microconductivity, were made during a series of 13 drift stations to investigate vertical turbulent transports and the evolution of water column stability. The dependence of pycnocline turbulent diffusivity k_T on Froude number Fr (turbulence generated by internal wave shear) and density ratio R_ρ (turbulence generated by diffusive layering and possibly diapycnal cabbeling) is investigated. The Fr alone cannot explain completely the observed k_T variability. Instead, there is also a strong dependence on R_ρ. Turbulent diffusivity is an order of magnitude larger in the weakly stratified Taylor cap over Maud Rise (where R_ρ approaches one) than in the surrounding water column that is unaffected by flow around Maud Rise. In terms of water column stability, diffusive heat flux across the pycnocline inhibits winter ice growth and densification of the surface layer. The observed R_ρ dependence of k_T thus provides a strong negative feedback on the winter evolution of the Maud Rise area water column toward overturning instability.
机译：2005年南方冬季，进行了一次考察东部韦德海弱分层水柱稳定性的考察。围绕Maud Rise的地区CTD勘测确定了与海山周围水流有关的水体边界，并确定了最容易倾覆的区域。发现海山泰勒柱的下游区域最不稳定，整个比索克林的电位密度差小于0.018 kg m〜（-3）。在一系列13个漂移站期间，进行了密集的水柱测量，包括1300个温度，电导率和快速响应微导率曲线，以研究垂直湍流传输和水柱稳定性的演变。研究了斜面湍流扩散率k_T对Froude数Fr（由内部波浪剪切产生的湍流）和密度比R_ρ（由扩散分层和可能的斜向晃动产生的湍流）的依赖性。单独的Fr不能完全解释观察到的k_T变异性。相反，也强烈依赖于R_ρ。湍流扩散率在Maud Rise上方的弱分层泰勒顶盖（R_ρ接近1）处比在不受Maud Rise周围水流影响的周围水柱中大。就水柱的稳定性而言，穿过吡菌环的扩散热通量抑制了冬季冰的生长和表层的致密化。因此，观测到的k_T的R_ρ依赖性对Maud Rise地区水柱的冬季演化向倾覆不稳定性提供了强烈的负反馈。

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    《Journal of Physical Oceanography》 |2014年第8期|1973-1991|共19页
  • 作者

    William J. Shaw; Timothy P. Stanton;

  • 作者单位

    Department of Oceanography, Naval Postgraduate School, 833 Dyer Road, OC Dept., Rm. 328 Spanagel Hall, Monterey, CA 93943;

    Department of Oceanography, Naval Postgraduate School, Monterey, California;

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