ABSTRACT Although it is an important branch of the global overturning circulation, the deep western boundary current (DWBC) in the Pacific was poorly understood because of sparse observations. Six state-of-the-art global ocean model outputs were used herein to evaluate their performance in simulating the DWBC in the Melanesian Basin (MB) and the Central Pacific Basin (CPB). These model outputs were compared with historical observations, in terms of water-mass characteristics, spatial structure, and meridional volume transport of the DWBC, as well as seasonal variation. The results showed that most of the models reproduced the DWBC well in the two basins. Except for the Ocean General Circulation Model for the Earth Simulator (OFES) with its obvious cold and salty biases, the models had minor deviations in temperature and salinity in the deep layer. These models can reconstruct the spatial structure of the DWBC in detail and simulate appropriate transports of the eastern branch of the DWBC, ranging from 6.36 Sv to 8.55 Sv (1 Sv = 106 m3 s−1). The western branch of the DWBC was underestimated by all the models except the Hybrid Coordinate Ocean Model (HYCOM), which simulated a transport of 4.48 Sv. For the DWBC, HYCOM performed best with a total transport of 12.84 Sv. Analysis of the temperature and salinity from Levitus data demonstrated the existence of annual and semi-annual cycles in the deep water of the MB and CPB, respectively, with a warmer and saltier water mass in summer and autumn. Overall, the six models were able to simulate the seasonal variations of temperature and volume transport of the DWBC in the Pacific. The seasonal signals probably originated from the DWBC upstream and propagated along its pathway.

中文翻译：

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模拟太平洋深部西部边界流的全球海洋模型评估

摘要 虽然它是全球翻转环流的一个重要分支，但由于观测稀少，对太平洋西部深边界流（DWBC）的了解甚少。本文使用六个最先进的全球海洋模型输出来评估它们在模拟美拉尼西亚盆地 (MB) 和中太平洋盆地 (CPB) 的 DWBC 方面的性能。这些模型输出与历史观测值在水团特征、空间结构和 DWBC 的经向体积传输以及季节性变化方面进行了比较。结果表明，大部分模型都很好地再现了两个盆地的DWBC。除了地球模拟器海洋环流模型（OFES）具有明显的冷盐偏差外，其他模型在深层的温度和盐度都有轻微的偏差。这些模型可以详细重建 DWBC 的空间结构并模拟 DWBC 东支的适当输运，范围从 6.36 Sv 到 8.55 Sv（1 Sv = 106 m3 s−1）。除了混合坐标海洋模型 (HYCOM) 模拟 4.48 Sv 的传输外，所有模型都低估了 DWBC 的西部分支。对于 DWBC，HYCOM 表现最好，总传输量为 12.84 Sv。对 Levitus 数据的温度和盐度分析表明，MB 和 CPB 深水区分别存在年和半年循环，夏季和秋季水团更暖和更咸。总体而言，这六个模型能够模拟太平洋 DWBC 的温度和体积传输的季节性变化。