The Weakened Upwelling at the Upstream Kuroshio in the East China Sea Induced Extensive Sea Surface Warming

The interannual sea surface temperature trend of the Kuroshio in the East China Sea (ECS-Kuroshio) is significantly different from that of the ECS-shelf region. Based on 33 years (1982-2014) of observational temperature data in the ECS, the upstream ECS-Kuroshio, as an upwelling region, shows an opposite temperature trend to the downstream ECS-Kuroshio, creating a horizontal "dipole" structure. Vertical heat transport modulated by upwelling variability in the upstream ECS-Kuroshio can be the main factor for the distinct temperature trend in the upstream ECS-Kuroshio. This upstream trend can expand to downstream areas through horizontal advections. As a result, the weakened upwelling triggered a significant warming trend in the entire upper layer of the ECS-Kuroshio during the warming period (1999-2014). The weakening trend of upwelling and global rewarming conditions may lead to robust warming in the Kuroshio region in the middle of this century.