The separation of the East Australian Current : A Lagrangian approach to potential vorticity and upstream control
The separation of the East Australian Current : A Lagrangian approach to potential vorticity and upstream control
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东澳大利亚洋流的分离：位涡和上游控制的拉格朗日方法
DOI：
10.1002/2015jc011133
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发表时间：
2016
影响因子：
--
通讯作者：
P. Spence
中科院分区：
文献类型：
--
作者：
S. Ypma;E. Sebille;A. Kiss;P. Spence
东澳大利亚海流（East Australian Current，EAC）是沿澳大利亚东海岸沿着流动的西部边界海流，在大约34°S处与海岸分离。分离后，两个主要的路径可以区分，向东流动的塔斯曼锋和延伸的EAC向南流动。分离纬度以南的区域是涡旋丰富的，EAC的分离纬度是可变的。在EAC分叉处分离的水团的性质知之甚少。本文提出了新的见解，从拉格朗日的角度来看，转向东和那些继续向南的水团跟踪在一个涡流允许的数值模型。计算了沿两条路径的沿着输运，发现EAC延伸区的输运与塔斯曼锋的输运之比为1：3.结果表明，粒子的“归宿”是由分离纬度上游EAC流内粒子分布决定的一级动力，其中EAC延伸区的85%粒子来自460 m以下，塔斯曼锋的90%粒子来自28°S处460 m深度的顶部.分离和通道由该区域的等密度线的结构控制。对位涡异常的分析表明，在两个水团重叠的区域，水的命运取决于反气旋涡旋的存在，反气旋涡旋将等密度线向下推，从而使粒子能够进一步向南移动。
The East Australian Current (EAC) is the western boundary current flowing along the east coast of Australia separating from the coast at approximately 34°S. After the separation two main pathways can be distinguished, the eastward flowing Tasman Front and the extension of the EAC flowing southward. The area south of the separation latitude is eddy-rich and the separation latitude of the EAC is variable. Little is known of the properties of the water masses that separate at the bifurcation of the EAC. This paper presents new insights from the Lagrangian perspective, where the water masses that veer east and those that continue south are tracked in an eddy-permitting numerical model. The transport along the two pathways is computed, and a 1:3 ratio between transport in the EAC extension and transport in the Tasman Front is found. The results show that the "fate" of the particles is to first order already determined by the particle distribution within the EAC current upstream of the separation latitude, where 85% of the particles following the EAC extension originate from below 460 m and 90% of the particles following the Tasman Front originate from the top 460 m depth at 28°S. The separation and pathways are controlled by the structure of the isopycnals in this region. Analysis of anomalies in potential vorticity show that in the region where the two water masses overlap, the fate of the water depends on the presence of anticyclonic eddies that push isopycnals down and therefore enable particles to travel further south.