Summer upwelling has often been observed off Vietnam in the South China Sea (SCS). Occasional disappearance of the upwelling has attracted much attention because it modulates the regional climate and harms surrounding fisheries. Fluctuations of the East Asian monsoon associated with El Ni?o are considered responsible for the weakened or abolished upwelling. However, analyses of observations performed in the present study were equivocal in terms of the dominant influence of El Ni?o. Based on long-term sea surface temperature data, we demonstrated that weak upwelling off Vietnam occurs more frequently during periods of accelerated global warming compared to warming hiatus periods. Warming signals in the Indian Ocean vanished relatively quickly during the hiatus period. The accompanying easterly anomalies south of the anomalous anticyclone (AAC) in the northwestern Pacific were also weakened, reducing the impact of the El Ni?o teleconnection on the SCS summer monsoon and thus preserving the regular post-summer upwelling off Vietnam during warming hiatus periods.

El Ni?o与越南夏季后上升流的非固定性遥相关

中文摘要：在南中国海（SCS）越南海域经常观测到上升流。上升流的偶然消失引起了人们的广泛关注，因为它调节了区域气候，并对周围的渔业造成了危害。与El Ni?o相关的东亚季风被认为是上升流减弱或消失的原因。然而，在本研究中观测资料的分析，认为El Ni?o对上升流的支配地位存在怀疑。基于长期海表温度数据，我们认为，与变暖间歇期相比，越南沿岸的弱上升流更频繁发生在全球变暖加速期。印度洋海域的变暖信号在变暖间歇期消失得相对较快。西北太平洋异常反气旋(AAC)以南伴随的东风异常也减弱，减弱了El Ni?o遥相关对南海夏季风影响，从而保留了在变暖间歇期越南海域的规律性夏季后上升流。