The ocean vertical circulation has been historically underappreciated compared to the lateral circulation, largely due to the poor availability of the ocean vertical-velocity information. With the advent of high-performance ocean models, especially those constrained by the most available observations, it is now possible and incentive to dig into the vertical branch of ocean circulation. In this study, we used a state-of-the-art and dynamically-consistent ocean state estimate to investigate the seasonal variations and trend of the global upper-ocean (in the top 200 m) vertical velocity, with emphasis on the widely recognized upwelling and downwelling systems. Significant seasonal variations were noted. All around the global ocean, the North Indian Ocean and the Equator exhibited the strongest seasonality. There existed an equatorial Rossby wave propagating the equatorial Pacific upwelling at a phase speed of approximately −0.60 m/s (westward). Over 1998–2017, there were not basin-scale patterns of statistically-significant trend in the upper-ocean vertical velocity. In addition, our results did not support the classical Bakun’s 1990 hypothesis on the upwelling intensification along the major eastern boundary upwelling systems in the context of global warming. This, however, may be due to the short period considered in this study. Four extended datasets were also examined. Patterns of seasonal variations were largely robust among these datasets. Results from these extended datasets further confirmed that there were not basin-scale patterns of statistically significant intensification or weakening of vertical circulations in the top 200 m of the global ocean during 1998–2017.

与横向环流相比，海洋垂直环流在历史上一直被低估，这主要是由于海洋垂直速度信息的可用性较差。随着高性能海洋模型的出现，特别是那些受最可用观测限制的模型，现在有可能并有动力深入研究海洋环流的垂直分支。在这项研究中，我们使用最先进且动态一致的海洋状态估计来研究全球上层海洋（顶部 200 m）垂直速度的季节变化和趋势，重点是广泛认可的上升流和下降流系统。注意到明显的季节性变化。在全球海洋周围，北印度洋和赤道表现出最强的季节性。存在一个赤道罗斯比波以大约-0.60 m/s（向西）的相速度传播赤道太平洋上升流。在 1998 年至 2017 年期间，上层海洋垂直速度没有具有统计显着趋势的盆地尺度模式。此外，我们的结果不支持经典的 Bakun 1990 年关于在全球变暖背景下沿主要东部边界上升流系统上升流增强的假设。然而，这可能是由于本研究考虑的时间较短。还检查了四个扩展数据集。在这些数据集中，季节性变化的模式在很大程度上是稳健的。