The western boundary current in the equatorial Atlantic Ocean is a main conduit for water‐mass exchanges across the equator and thus a major pathway for the interhemispheric transports in the Atlantic Meridional Overturning Circulation (AMOC) system. In this study we quantify and examine the mean and seasonal variability of the equatorial western boundary current (EWBC) in the upper ocean layer using two data‐assimilated products, the Estimating the Circulation and Climate of the Ocean (ECCO4r3) and the Simple Ocean Data Assimilation (SODA3). It is found that the EWBC between 10°S and 10°N exhibits two pronounced features in its seasonal variability: (1) the transport varies anti‐symmetrically across the equator, that is, the northward EWBC strengthens to the north of the equator when it weakens to the south of the equator, and vice versa; and (2) the amplitude of seasonal variations is much greater in the northern hemisphere than in the south. We hypothesize that the cross‐equatorial anti‐symmetry in EWBC transport variability is attributable to the impingement of equatorial Rossby waves at the western boundary and the shape of the western boundary is the main cause for the amplified seasonal variability in the northern hemisphere. A simple 1 and 1/2‐layer model is used to test and validate this hypothesis and to elucidate the role of wind forcing and topography plays in the seasonal variability in the EWBC transport.

中文翻译：

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大西洋西边界流季节性运输中的跨赤道反对称性

赤道大西洋西部的边界流是穿越赤道的水质交换的主要管道，因此是大西洋子午翻转环流（AMOC）系统中半球间运输的主要途径。在这项研究中，我们使用两种数据同化产品，即估计海洋环流和气候（ECCO4r3）和简单海洋数据，量化和检验了上层洋海赤道西边界流（EWBC）的均值和季节性变化。同化（SODA3）。发现在10°S和10°N之间的EWBC在季节变化方面表现出两个明显的特征：（1）赤道的输运呈反对称变化，即北EWBC在赤道北向时增强它减弱到赤道以南，反之亦然；（2）北半球的季节变化幅度比南部大得多。我们假设EWBC输运变异性中的跨赤道反对称性可归因于赤道Rossby波在西边界的撞击，而西边界的形状是北半球放大的季节性变化的主要原因。一个简单的1层和1/2层模型用于检验和验证该假设，并阐明风力和地形在EWBC运移的季节性变化中的作用。我们假设EWBC输运变异性中的跨赤道反对称性可归因于赤道Rossby波在西边界的撞击，而西边界的形状是北半球放大的季节性变化的主要原因。一个简单的1层和1/2层模型用于检验和验证该假设，并阐明风力和地形在EWBC运移的季节性变化中的作用。我们假设EWBC输运变异性中的跨赤道反对称性可归因于赤道Rossby波在西边界的撞击，而西边界的形状是北半球放大的季节性变化的主要原因。一个简单的1层和1/2层模型用于检验和验证该假设，并阐明风力和地形在EWBC运移的季节性变化中的作用。