Observational and model studies of synoptic current fluctuations in the Bohai Strait on the Chinese continental shelf

Three winter storms struck the Bohai and Yellow seas in succession during February 16-25, 2017. Periodic fluctuations of sea level, currents, temperature, and salinity were recorded at a moored station deployed in the Bohai Strait. Observations also captured significant synoptic fluctuations of inflow and outflow through the Bohai Strait with maximum magnitude exceeding 50cms(-1). The sea level dropped by >1m and the bottom temperature decreased by 2.5 degrees C in <30h during these winter storms. A regional ocean model was used to investigate the prominent fluctuations of synoptic exchange flow through the Bohai Strait. The model results indicated that the Bohai and Yellow seas in their entirety responded strongly to the storm bursts and subsequent relaxation at the synoptic scale. The periodic winter storm bursts and relaxation excited the cyclonic propagation of coastal-trapped waves around the Bohai and Yellow seas. Strong periodic inflow and outflow during the passage of the three successive storms promoted water exchange between the Bohai Sea and the northern Yellow Sea. Successive winter storms might also affect the mean current structure through the Bohai Strait. The mean currents through the Bohai Strait during the studied storm period were characterized by inflow in both northern and southern parts of the strait and outflow through the middle of the strait. This arrangement is different from the traditional view of inflow via the northern channel and outflow through the southern channel.