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首页> 外文期刊>Journal of Physical Oceanography >Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific
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Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific

机译：南太平洋浅盐度最低值的形成：南太平洋通往热带太平洋的途径

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摘要

In the eastern South Pacific Ocean, at a depth of about 200 m, a salinity minimum is found. This minimum is associated with a particular water mass, the "Shallow Salinity Minimum Water" (SSMW). SSMW outcrops in a fresh tongue (S_(min)) centered at about 45°S. The S_(min) appears to emanate from the eastern boundary, against the mean flow. The watermass transformation that creates SSMW and S_(min) is investigated here. The S_(min) and SSMW are transformed from saltier and warmer waters originating from the western South Pacific. The freshening and cooling occur when the water is advected eastward at the poleward side of the subtropical gyre. Sources of freshening and cooling are air-sea exchange and advection of water from south of the subtropical gyre. A freshwater and heat budget for the mixed layer reveals that both sources equally contribute to the watermass transformation in the mixed layer. The freshened and cooled mixed layer water is subducted into the gyre interior along the southern rim of the subtropical gyre. Subduction into the zonal flow restricts the transformation of interior properties to diffusion only. A simple advection/diffusion balance reveals diffusion coefficients of order 2000 m~2 s~(-1). The tongue shape of the S_(min) is explained from a dynamical viewpoint because no relation to a positive precipitation-evaporation balance was found. Freshest S_(min) values are found to coincide with slowest eastward mixed layer flow that accumulates the largest amounts of freshwater in the mixed layer and creates the fresh tongue at the sea surface. Although the SSMW is the densest and freshest mode of water subducted along the South American coast, the freshening and cooling in the South Pacific affect a whole range of densities (25.0-26.8 kg m~(-3)). The transformed water turns northward with the gyre circulation and contributes to the hydrographic structure of the gyre farther north. Because the South Pacific provides most of the source waters that upwell along the equatorial Pacific, variability in South Pacific hydrography may influence equatorial Pacific hydrography. Because one-half of the transformation is found to be controlled through Ekman transport, variability in wind forcing at the southern rim of the subtropical gyre may be a source for variability of the equatorial Pacific.
机译：在南太平洋东部约200 m的深度处，发现最低盐度。该最小值与特定的水量（“浅盐度最小水”（SSMW））相关。 SSMW以约45°S为中心的新鲜舌头（S_（min））露头。 S_（min）似乎是从东部边界向平均流量方向发散的。这里研究了产生SSMW和S_（min）的水质转换。 S_（min）和SSMW是从起源于南太平洋西部的咸水和暖水转变而来的。当水在亚热带回旋的极点侧向东平流时，就会发生新鲜和冷却。清新和冷却的来源是海气交换和来自亚热带回旋区南部的水的平流。混合层的淡水和热量预算表明，两种来源均对混合层的水质转化做出了贡献。新鲜和冷却后的混合层水沿着亚热带回旋管的南缘俯冲到回旋管内部。俯冲到地层流中将内部属性的转换限制为仅扩散。一个简单的对流/扩散平衡揭示了约2000 m〜2 s〜（-1）的扩散系数。从动力学角度解释了S_（min）的舌形，因为没有发现与正的沉淀-蒸发平衡有关。发现最新鲜的S_（min）值与最慢的向东混合层流相吻合，该向东混合层流在混合层中积累了大量的淡水，并在海面产生了新鲜的舌头。尽管SSMW是沿南美海岸俯冲的最密集和最新鲜的水模式，但南太平洋的新鲜和冷却影响了整个密度范围（25.0-26.8 kg m〜（-3））。转换后的水随着回旋环流而向北转向，并有助于更北回旋流的水文结构。由于南太平洋提供了沿赤道太平洋上升的大部分水源，因此南太平洋水文学的变化可能会影响赤道太平洋水文学。由于发现转换的一半是通过埃克曼输运控制的，因此亚热带回旋南缘的强迫风的变化可能是赤道太平洋变化的原因。

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  • 来源
    《Journal of Physical Oceanography》 |2004年第11期|p.2398-2412|共15页
  • 作者

    JOHANNES KARSTENSEN;

  • 作者单位

    IFM-GEO-MAR, Leibniz-Institut fuer Meereswissenschaften an der Universitaet Kiel, Dienstgebaeude Westufer, Duesternbrooker Weg 20, 24105 Kiel, Germany;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 海洋学;
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