Abstract The objective of the present study is to analyze the interannual variability of the Southwestern Atlantic Continental Shelf (SWACS) circulation and its thermohaline structure. To accomplish it we employed the global ocean reanalysis ORAP5.0, which spans the 35-years period 1979–2013. ORAP5.0 satisfactorily reproduces the most distinctive features of the SWACS circulation and its variability on different timescales, including the interannual scale. The first mode of a joint empirical orthogonal function (EOF) analysis of sea surface temperature (SST), sea surface salinity (SSS), and vertically averaged horizontal velocities is significantly correlate with the first mode of interannual variability of the atmosphere in the Southern Hemisphere, the Southern Annular Mode (SAM). Remarkably the shelf sea response has been found to be statistically significant not only in the Patagonian Shelf (south of 40 °S), as discussed in the literature, but also in the Northern Shelf (north of 40°S). During the active phases of the leading mode, current anomalies develop as a result of the sea surface height adjustment to Ekman transport at the coastline induced by alongshore wind anomalies. Modification of the advection terms in the salinity and heat budgets due to changes in the circulation and heat surface fluxes generate SST and SSS anomalies along the SWACS. It is suggested that these anomalies drive changes in the mixed layer depth and that these changes can modulate the interannual variability of the chlorophyll-a concentration during austral spring in the frontal zones.

中文翻译：

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SAM 驱动的西南大西洋陆架海洋环流变化

摘要 本研究的目的是分析西南大西洋大陆架（SWACS）环流的年际变化及其温盐结构。为了实现这一目标，我们采用了跨越 1979 年至 2013 年的 35 年间的全球海洋再分析 ORAP5.0。ORAP5.0 令人满意地再现了 SWACS 环流的最显着特征及其在不同时间尺度（包括年际尺度）上的可变性。海面温度 (SST)、海面盐度 (SSS) 和垂直平均水平速度的联合经验正交函数 (EOF) 分析的第一模态与南半球大气年际变率的第一模态显着相关，南方环形模式（SAM）。值得注意的是，已经发现大陆架海洋响应不仅在巴塔哥尼亚大陆架（40°S 以南）中具有统计学意义，如文献中所讨论的，而且在北大陆架（40°S 以北）中也是如此。在领先模态的活跃阶段，由于沿海风异常引起的海岸线埃克曼输运的海面高度调整，导致海流异常发展。由于环流和热表面通量的变化，盐度和热量收支中的平流项的修改产生了沿 SWACS 的 SST 和 SSS 异常。这表明这些异常驱动了混合层深度的变化，并且这些变化可以调节额叶区南方春季期间叶绿素-a 浓度的年际变化。