Optimal Precursors Triggering Sudden Shifts in the Antarctic Circumpolar Current Transport through Drake Passage
Optimal Precursors Triggering Sudden Shifts in the Antarctic Circumpolar Current Transport through Drake Passage
复制标题
最佳前体触发通过德雷克航道的南极绕极洋流输送的突然变化
DOI：
10.1029/2021jc017899
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Kun Zhang
中科院分区：
文献类型：
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作者：
Li Zhou;Qiang Wang;Mu Mu;Kun Zhang
摘要由于南极绕极流具有高度的非线性，因此对南极绕极流输运的准确预报仍具有挑战性。利用涡动允许区域海洋模拟系统和条件非线性最优扰动方法，通过探索其最优前体（OPR），研究了ACC通过德雷克海峡（DP）输运的突变。在这里，ACC运输的突然转变被定义为波动超过双标准差（？16 Sv; 1 Sv = 106 m3 s？1)在30天内。结果表明，三种情况下的OPR在中间DP（58°S？南纬62度西经72度64°W），深度为1000？3000 m，这意味着ACC输运对初始扰动最为敏感。OPR？演变显示了类似的特征：每种情况下的OPR触发一个涡状偶极子扰动与北方气旋和南方反气旋，导致ACC运输的突然减少？40西弗。验证了OPR中的密度分量决定了这种演化过程。此外，通过对扰动动能收支的分析，诊断出斜压不稳定在OPR的发展中起着主导作用。这项研究表明，在考虑短期预测ACC输送时，应仔细监测南大洋的深层密度扰动。
AbstractDue to the high nonlinearity, the accurate prediction of the Antarctic Circumpolar Current (ACC) transport is still challenging. Using the eddy-permitting Regional Ocean Modeling System and the conditional nonlinear optimal perturbation approach, the sudden shift in the ACC transport through Drake Passage (DP) is investigated by exploring its optimal precursor (OPR). Here, the sudden shift in the ACC transport is defined as a fluctuation exceeding double standard deviation (?16 Sv; 1 Sv = 106 m3 s?1) within 30 days. The results indicate that the OPRs for all three cases exhibit specific structures in the middle DP (58°S?62°S, 72°W?64°W) at the depth of 1000?3000 m, implying that the ACC transport is most sensitive to the initial perturbations there. The OPRs? evolutions show similar features: the OPR for each case triggers an eddy-like dipole perturbation with a northern cyclone and a southern anticyclone, leading to a sudden reduction in the ACC transport of ?40 Sv. It is verified that the density components in the OPRs determine such evolution processes. Furthermore, baroclinic instability is diagnosed to play a dominant role in the development of OPRs by analyzing the perturbed kinetic energy budget. This study suggests that the deep-layer density perturbations in the Southern Ocean should be carefully monitored when considering the short-range prediction of the ACC transport.