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Asymmetric tidal straining across an inlet: Lateral inversion and variability over a tidal cycle

机译:入口处的不对称潮汐应变:潮汐周期的横向反转和变化

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摘要

Tidal straining is a phenomenon of temporal variations in stratification and mixing resulting from the interaction of a longitudinal salinity gradient with the vertical shear of the horizontal tidal velocity. As a result, the theory predicts stronger and weaker stratification during ebb/low tide and flood/high tide, respectively. In contrast to this well-known temporal asymmetry, in this study, we document in situ measurements demonstrating a lateral asymmetry and lateral inversion of tidal straining at Barataria Pass, a narrow (~600 m wide) tidal inlet of Barataria Bay in southeastern Louisiana. During flood, the eastern side of the channel had strong stratification of 4 PSU salinity change over a 1.5 m thin layer while the western side had a 2 PSU change over a 12 m water column. This strong lateral difference decreased as flood continued until near the end of the flood when it reached vertically well-mixed condition across the channel. During ebb it was just the opposite such that the western side became stratified while the eastern end was well-mixed. This resulted to a small correlation coefficient of -0.05 for stratification between the west and east sides, although the central channel and east side have a high correlation coefficient of 0.88. The tidally averaged salinity was higher on the western end than the eastern end except in a narrow boundary layer close to the eastern shore. This is an apparent contradiction to what the Coriolis effect would produce in classical estuarine dynamics. Our hypothesis for the observed difference arises from the influence of the river water coming out of the Mississippi River through the Southwest Pass of the Birdfoot Delta. This water mass may have played a role in the observed, complicated lateral inversion of the tidal straining. This study underlines the complexity of estuarine dynamics proximal to large deltaic systems and we anticipate that these results will underscore the need for a modeling study to further investigate this dynamic process.
机译:潮汐应变是分层和混合随时间变化的现象,这是由于纵向盐度梯度与水平潮汐速度的垂直剪切力相互作用而引起的。结果,该理论预测在退潮/退潮和洪水/涨潮期间分别会出现更强和更弱的分层。与这种众所周知的时间不对称性不同,在这项研究中,我们记录了原位测量结果,证明了路易斯安那州东南部巴拉塔里亚湾的一条狭窄(〜600 m宽)潮汐入口巴拉塔里亚通道的潮汐应变的横向不对称和横向反转。在洪水期间,河道东侧在1.5 m薄层上有4 PSU盐度变化的强烈分层,而西侧在12 m水柱上有2 PSU盐度变化。随着洪水的持续,这种强烈的横向差异减小,直到洪水在通道两端达到垂直均匀混合状态时才接近洪水的尽头。在退潮期间,正好相反,以至于西侧变得分层,而东端则混合得很好。尽管中央通道和东侧的相关系数很高,但西侧和东侧之间的分层的相关系数较小,为-0.05,但相关系数较高。潮汐平均盐度在西端比东端更高,除了靠近东岸的狭窄边界层外。这与古典河口动力学中的科里奥利效应产生明显矛盾。我们对观察到的差异的假设来自于通过Birdfoot Delta的西南通道从密西西比河流出的河水的影响。该水团可能在观察到的,复杂的潮汐应变横向反转中起作用。这项研究强调了靠近大型三角洲系统的河口动力学的复杂性,我们预计这些结果将强调需要进行模型研究以进一步研究这一动力学过程。

著录项

  • 来源
    《Estuarine Coastal and Shelf Science》 |2009年第4期|651-660|共10页
  • 作者单位

    Coastal Studies Institute, Department of Oceanography and Coastal Sciences, School of the coast and Environment, Louisiana State University, Baton Rouge, LA 70803, United States College of Marine Sciences, Shanghai Ocean University, 334 Jungong Road, Shanghai 200090, China Coastal Studies Institute, Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, United States;

    Department of Oceanography and Coastal Sciences, School of the coast and Environment, Louisiana State University, Baton Rouge, LA 70803, United States;

    Coastal Studies Institute, Department of Oceanography and Coastal Sciences, School of the coast and Environment, Louisiana State University, Baton Rouge, LA 70803, United States;

    Department of Oceanography and Coastal Sciences, School of the coast and Environment, Louisiana State University, Baton Rouge, LA 70803, United States;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    tides; estuaries; estuarine dynamics; in situ measurements; tidal straining; tidal pass;

    机译:潮汐河口河口动力学;原位测量;潮汐拉紧;潮汐;

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