The southern branch of the South Equatorial Current (SSEC) is the northern limit of the South Atlantic Subtropical Gyre. When this current reaches Brazil around 14°S it bifurcates into a southward flow as the Brazil Current (BC) and the surface portion of the northward flowing North Brazil Undercurrent (NBUC). The SSEC system is a key component of the western boundary supply, influencing the NBUC/BC variability and, therefore, global climate through the Meridional Overturning Circulation. In this study, using altimetry satellite data and reanalyzes outputs (1993–2018), we revisit the SSEC mean state and show this current arriving at the South Atlantic western boundary as a multi-banded flow with surface signatures resulting from different subsurface cores. These bands have velocities between 0.02 and 0.07 m s⁻¹ and, as shown by ADCP data from the PIRATA project, their signature in synoptic scenarios is obscured by eddies and waves with velocities between 0.1 and 0.3 m s⁻¹. In addition, the SSEC annual cycle analysis shows that the seasonality of the bands is out of phase with each other, presenting westward transport anomalies between 0.4 and 2.6 Sv. Finally, our results show that the seasonality of this multi-banded flow both defines where the BC is born, and modulates the seasonality of semi-permanent mesoscale eddies off Brazil.

中文翻译：

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重温大西洋南赤道洋流

南赤道流 (SSEC) 的南支是南大西洋副热带环流的北端。当该洋流在 14°S 左右到达巴西时，它分叉为向南流动的巴西洋流 (BC) 和向北流动的巴西北部潜流 (NBUC) 的地表部分。SSEC 系统是西部边界供应的关键组成部分，通过经向翻转环流影响 NBUC/BC 的变率，从而影响全球气候。在这项研究中，我们使用测高卫星数据并重新分析输出（1993-2018 年），重新审视 SSEC 平均状态，并将到达南大西洋西部边界的该电流显示为具有由不同地下核心产生的表面特征的多带流。这些波段的速度在 0.02 和 0.07 m s ^{-1 之间}并且，如来自 PIRATA 项目的 ADCP 数据所示，它们在天气情景中的特征被速度在 0.1 到 0.3 m s ^-1之间的涡流和波浪所掩盖。此外，SSEC 年周期分析表明，各波段的季节性相互异相，呈现 0.4 至 2.6 Sv 之间的西移异常。最后，我们的结果表明，这种多带流的季节性既定义了 BC 的诞生地，又调节了巴西附近半永久性中尺度涡旋的季节性。