We quantify the annual-mean structure, transport budget and coupling between surface and deep currents along the southern Australian shelves, that we propose be collectively known as the Southern Australia Current System. The system contains eastward Shelf Break Currents (SBC) including the Leeuwin Current Extension, the South Australian Current and the Zeehan Current; and a counter-flowing westward Flinders Current (FC). In this work, we use a high resolution climatological hydrography and a high resolution ocean model forced by an atmospheric climatology.The westward FC is dual structured with (1) the slope-FC, an undercurrent to the SBC trapped near 600 m depth; and (2) the offshore-FC, a large deep-reaching flow located offshore of the SBC. Along the slanted shelf (not zonally oriented), onshore flows feeding into the FC are weak, and the FC is disconnected from the Tasman Leakage south of Tasmania. Along the zonal shelf, where nearly 80% of total onshore flows occur, the FC intensifies resulting in 12.3 Sv transport at Cape Leeuwin.The eastward SBC are continuous flows in the upper 250 m. Over steep slopes, downwelling occurs from the SBC into the slope-FC and may be important in maintaining the slope-FC. The Leeuwin Current Extension transport decreases from 1.1 Sv at Cape Leeuwin to 0.1 Sv near the Great Australian Bight due to strong downwelling and offshore exports around Cape Leeuwin. The South Australian Current is weak and steady, and the Zeehan Current increases to 0.4 Sv due to onshore flows stronger than downwelling exports.We find that the SBC and offshore-FC are coupled through onshore Ekman drift and the SBC and slope-FC are coupled through downwelling. The combined effect is a conversion of widespread northward Ekman drift into downwelling with little impact on the eastward SBC transport. In contrast, the onshore flows feeding into the FC are largely converted into increasing westward FC transport. Even though the Leeuwin Current System off western Australia is fed by geostrophic flows and the Southern Australia Current System is fed by Ekman drift, the annual-mean circulation of the two systems are remarkably similar.In summer, when the winds are upwelling favourable, the SBC are weaker and partly reversed (to westward). In autumn, the winds become downwelling favourable and the FC is weaker and partly reversed (to eastward). In contrast, the Leeuwin Current System persists annually. The balance mechanism maintaining the seasonal opposition between the SBC and FC warrants further research.

中文翻译：

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基于网格水文和高分辨率模型的南澳大利亚洋流系统

我们量化了澳大利亚南部大陆架沿线的年平均结构、运输预算以及地表和深部洋流之间的耦合，我们建议将其统称为南澳大利亚洋流系统。该系统包含向东的陆架断裂流 (SBC)，包括 Leeuwin 海流延伸、南澳大利亚海流和 Zeehan 海流；和逆流向西的弗林德斯洋流 (FC)。在这项工作中，我们使用高分辨率气候水文和大气气候强迫的高分辨率海洋模型。向西 FC 是双重结构的：（1）斜坡-FC，潜流到 SBC 附近 600 m 深度；(2) 离岸 FC，一个位于 SBC 离岸的大型深水流。沿着倾斜的陆架（不是带状的），流入 FC 的陆上水流很弱，FC 与塔斯马尼亚南部的 Tasman Leakage 断开连接。沿着带状陆架，近 80% 的陆上水流发生在此处，FC 加强，导致在 Cape Leeuwin 的 12.3 Sv 输运。向东的 SBC 是上部 250 m 的连续流动。在陡坡上，下流从 SBC 进入斜坡 FC，可能对维持斜坡 FC 很重要。由于列文角周围强劲的下流和近海出口，Leeuwin Current Extension 输水量从 Cape Leeuwin 的 1.1 Sv 下降到 Great Australian Bight 附近的 0.1 Sv。南澳大利亚洋流弱而稳定，由于陆上流动强于下流出口，泽汉洋流增加到 0.4 Sv。我们发现 SBC 和海上-FC 通过陆上 Ekman 漂移耦合，SBC 和斜坡-FC 耦合通过下井。综合效应是将广泛的向北的 Ekman 漂移转变为向下流，而对向东的 SBC 运输几乎没有影响。相比之下，流入 FC 的陆上流量在很大程度上转化为增加的向西 FC 运输。尽管西澳大利亚近海的列文海流系统受地转流馈送，南澳大利亚海流系统受埃克曼漂流馈送，但这两个系统的年平均环流非常相似。 SBC 较弱且部分反转（向西）。在秋季，风变得有利于下降，FC 变弱并部分逆转（向东）。相比之下，Leeuwin Current System 每年都存在。维持 SBC 和 FC 之间季节性对立的平衡机制值得进一步研究。