New Perspectives on Frontal Variability in the Southern Ocean
New Perspectives on Frontal Variability in the Southern Ocean
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DOI：
10.1175/jpo-d-16-0222.1
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发表时间：
2017-05-01
影响因子：
3.5
通讯作者：
Chapman, Christopher C.
中科院分区：
文献类型：
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作者：
Chapman, Christopher C.
利用查普曼的研究中提出的小波/高阶统计增强（WHOSE）锋面检测方法对南大洋的锋面结构进行了研究。将该方法应用于21年的每日网格化绝对动力地形（ADT）数据，以获得锋面位置的每日地图。通过形成锋面出现频率图，然后用简单函数的叠加来近似这些出现图，得到了锋面的时间平均位置以及它们蜿蜒程度的度量，并与先前研究发现的锋面位置相关联。然后考虑了锋面结构的时空变异性。发现南大洋各处锋面的数量变化很大，在大型海底地形特征的下游增加（分裂），在锋面受下伏地形严格控制的区域减少（合并）。这些分裂/合并事件与下伏锋面结构的变化有关，即锋面出现频率高的区域跨越或扩散在流函数等值线上。与锋面数量不同，锋面的蜿蜒在整个南大洋相对恒定。在1993 - 2014年期间，几乎没有发现锋面的迁移，而且锋面位置对与南半球环状模或厄尔尼诺 - 南方涛动相关的大气强迫只有微弱的敏感性。最后，讨论了这些结果对跨流示踪物传输研究的影响。
The frontal structure of the Southern Ocean is investigated using the Wavelet/Higher Order Statistics Enhancement (WHOSE) frontal detection method, introduced in Chapman's work. This methodology is applied to 21 yr of daily gridded absolute dynamic topography (ADT) data to obtain daily maps of the locations of the fronts. By forming frontal occurrence frequency maps and then approximating these occurrence maps by a superposition of simple functions, the time-mean locations of the fronts, as well as a measure of their capacity to meander, are obtained and related to the frontal locations found by previous studies. The spatial and temporal variability of the frontal structure is then considered. The number of fronts is found to be highly variable throughout the Southern Ocean, increasing (splitting) downstream of large bathymetric features and decreasing (merging) in regions where the fronts are tightly controlled by the underlying topography. These splitting/merging events are related to changes in the underlying frontal structure whereby regions of high frontal occurrence cross or spread over streamfunction contours. In contrast to the number of fronts, frontal meandering remains relatively constant throughout the Southern Ocean. Little to no migration of the fronts over the 1993-2014 time period is found, and there is only weak sensitivity of frontal positions to atmospheric forcing related to the southern annular mode or the El Nino-Southern Oscillation. Finally, the implications of these results for the study of cross-stream tracer transport are discussed.