The synoptic variation of Yellow Sea Warm Current in winter and its mechanisms

Abstract

Purpose This paper aims to investigate the basin-scale features and mechanisms of the synoptic variation of Yellow Sea Warm Current (YSWC) in winter. Design/methodology/approach Both in situ current observation and numerical model (MITgcm) were conducted to investigate the synoptic variation of YSWC. The model was well validated and the simulated results were analyzed. Findings The YSWC shows a much stronger synoptic variation than its mean in winter with strong variation mainly in the deep central YS. The synoptic variation of YSWC is associated a counterclockwise rotary wave as a response to the strong northerly wind bursts. Strong northerly wind generates a large sea surface height (SSH) drop in the Bohai Sea and northern YS. Then, the SSH rotates in a counterclockwise manner. About 18 h later, strong eastward SSH gradient is formed, generating a northward current through geostrophic balance. Originality/value The mechanisms analysis shows that the synoptic variation of YSWC is intrinsically linked to SSH as a response to the synoptic varying winter monsoon. This study provides an insight into the spatial and temporal evolution of the oceanic response to strong northerly wind in winter.