On the fast decay of Agulhas rings
On the fast decay of Agulhas rings
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DOI：
10.1029/2009jc005585
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发表时间：
2010-03
影响因子：
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通讯作者：
E. Sebille;P. Leeuwen;A. Biastoch;W. D. Ruijter
中科院分区：
文献类型：
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作者：
E. Sebille;P. Leeuwen;A. Biastoch;W. D. Ruijter
最终流入大西洋的印度洋水主要以厄加勒斯环和气旋的形式从厄加勒斯洋流的逆反射中分离出来。在高分辨率数值海洋模型中使用数值拉格朗日浮体轨迹，研究了厄加勒斯洋流反射附近相干结构的命运。结果表明，在厄加勒斯洋流内，逆反射上游，终止于大西洋的浮体和终止于印度洋的浮体的空间分布在很大程度上相似。这表明阿古拉斯泄漏主要是通过阿古拉斯环的脱离发生的。浮标与厄加勒斯洋流分离后，周围的水很快就会失去相对涡度。因此，阿加勒斯环似乎正在腐烂，并失去了开普盆地中的大量水分。聚类分析表明，厄加勒斯洋流中的大部分水都在直径 180 公里的聚类范围内。在开普盆地的中途，相对涡度较低的较大星团的数量有所增加，这些星团携带着大部分厄加勒斯泄漏传输穿过开普盆地。这种相对于泄漏长度尺度的向上级联，与相对涡量大小的幂律衰减相结合，可能表明阿加勒斯环的衰减在某种程度上与二维湍流的衰减相当。
The Indian Ocean water that ends up in the Atlantic Ocean detaches from the Agulhas Current retroflection predominantly in the form of Agulhas rings and cyclones. Using numerical Lagrangian float trajectories in a high-resolution numerical ocean model, the fate of coherent structures near the Agulhas Current retroflection is investigated. It is shown that within the Agulhas Current, upstream of the retroflection, the spatial distributions of floats ending in the Atlantic Ocean and floats ending in the Indian Ocean are to a large extent similar. This indicates that Agulhas leakage occurs mostly through the detachment of Agulhas rings. After the floats detach from the Agulhas Current, the ambient water quickly looses its relative vorticity. The Agulhas rings thus seem to decay and loose much of their water in the Cape Basin. A cluster analysis reveals that most water in the Agulhas Current is within clusters of 180 km in diameter. Halfway in the Cape Basin there is an increase in the number of larger clusters with low relative vorticity, which carry the bulk of the Agulhas leakage transport through the Cape Basin. This upward cascade with respect to the length scales of the leakage, in combination with a power law decay of the magnitude of relative vorticity, might be an indication that the decay of Agulhas rings is somewhat comparable to the decay of two-dimensional turbulence.