海洋底混合层研究进展

Research progress of ocean bottom mixing layer

  • 摘要: 海洋底混合层是海洋底层水体中受强湍流混合作用影响的水层,温度、盐度和密度等物理性质在垂直方向上相对均匀,其作为海洋物理、化学和生物过程交汇的重要界面,在全球海洋能量、物质交换和生物地球化学循环中扮演着关键角色。本文系统综述了海洋底混合层的研究进展,重点探讨了其结构特征、影响机制、厚度的确定及参数化方法以及全球海洋底混合层厚度分布规律,并展望了其未来研究研究方向。详细分析了底混合层温度、盐度和密度在垂直方向相对均匀的结构特征;探讨了底层剪切流引发湍流破坏水体密度层结、内波破碎产生强湍流混合、地形改变底层流流速方向增大流速梯度、潮汐作用周期性调节底层流流速流向、地热通量加热底层海水减弱层结稳定性等多种影响机制;介绍了阈值法、曲率法、最大角度法和相对方差法等确定底混合层厚度的方法,并讨论了底混合层厚度与海水深度和湍流扩散系数呈正相关、与浮力频率呈负相关等参数化关系;总结了全球大洋底混合层厚度分布不均匀性特征,洋中脊附近较厚,大西洋、印度洋和太平洋的底混合层厚度中值分别为40米、42米和64米,全球中值为47米;最后对海洋底混合层未来的研究手段和研究方向做出了展望,提出需发展深海坐底潜标、自主水下机器人等先进观测技术,加强底层流剪切、内波破碎和地形效应相互作用的理论研究,发展底混合层精细数值模拟等。

     

    Abstract: This study comprehensively reviews the research progress on the ocean bottom mixing layer, emphasizing its structural features, influencing mechanisms, thickness determination and parameterization methods, and global distribution patterns, while also exploring future research directions. The ocean bottom mixing layer, a water layer near the ocean floor influenced by strong turbulent mixing, has relatively uniform temperature, salinity, and density. As a crucial interface for marine physical, chemical, and biological processes, it plays a key role in global ocean energy exchange, material transport, and biogeochemical cycles. We thoroughly analyze the structural characteristics of the ocean bottom mixing layer. Various influencing mechanisms such as bottom shear flow, internal wave breaking, topography, tides, and geothermal flux are explored. Methods for determining the thickness of the bottom mixing layer are introduced, and parameterization of the bottom mixing layer thickness in relation to the seawater depth, buoyancy frequency, and turbulent diffusion coefficients is discussed. Finally, the distribution characteristics of the global ocean bottom mixing layer thickness are summarized, and future research methods and directions of the ocean bottom mixing layer are prospected.

     

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