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Based on monthly averaged current, temperature, and salinity, we analyzed the changes of suspended sediment concentration (SSC) and the relationship with the warm current, coastal current, and cold water mass (CWM) in the East China Seas (ECSs). The result shows that the coastal current and surface diluted water are the route for transporting suspended sediment. The Kuroshio and its derived warm current branches play the important role of the continental shelf circulation system and control the diffusion of suspended sediment. High SSC has been mainly concentrated in coastal current and CWM. Two sedimentary dynamic patterns have been identified. The winter‐half‐year pattern lasts almost 7 months. The coastal currents off the Shandong Peninsula, northern Jiangsu, Zhejiang‐Fujian coast are the main routes for diffusion and deposition of the suspended sediment from the Yellow River and Changjiang River. The summer‐half‐year pattern is characterized by the well‐developed CWM. All CWMs have a unique function to trap suspended sediment under the thermocline due to weakening tidal current and residual current there. These CWMs in the Yellow Sea (YS) and north ECS are connected together. The layer above the thermocline is characterized by diluted water with low salinity, high temperature. Suspended sediment can be transported into the Okinawa Trough and the South Korea coast during this period. A strong eddy always occur nearby the Kuroshio bend at northeast Taiwan, which has promoted the exchange between the ECS shelf and Okinawa Trough, and the development of the shelf edge current and Taiwan warm current (TWC).

The Yellow Sea Cold Water Mass (YSCWM) is an important component of the hydrodynamic system in the South Yellow Sea (SYS). However, its intricate interactions with the ambient flows over long time scales are not fully understood. This paper presents the analysis of the data set obtained from a seabed‐mounted Acoustic Doppler Current Profiler (ADCP) deployed for nearly 1 year in the western SYS. It allowed us to study the evolution of YSCWM, including the seasonal changes of tidal currents, near‐inertial oscillations (NIOs), and the wind‐driven currents due to typhoons and winter storms. Strong NIOs were found near the bottom of mixed layer and in the pycnocline with nearly opposite current directions, with maximum velocity of nearly 20 cm·s−1 in summer. The YSCWM can also inhibit the direct downward energy transport in the water column due to typhoons. Conversely, the hydrodynamic system also feeds back to influence the change of YSCWM. A large current shear (S) of 20 cm·s−1·m−1 is generated near the top of pycnocline. Generally, the intensity and depth of the pycnocline determine S's magnitude and vertical location, respectively. Based on the monthly averaged density profile data, the Richardson number and wavelet analysis, the NIOs are considered to be capable of inducing predominant shear instability around the pycnocline. However, the NIOs are not strong enough to influence the lower YSCWM. In addition, in autumn, each fortnightly spring tide corresponds with a bottom temperature increase of nearly 2°C, indicating that tidal currents are the leading hydrodynamic driving force to decline the YSCWM.

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The muddy area in the centre of the South Yellow Sea (SYS) is formed and characterized by fine‐grained particles since the Yellow Sea circulation system became stable before 8000 years. The distribution and thickness of the central South Yellow Sea muddy area are both updated based on the interpretation of eight high‐resolution sub‐bottom profiles in central SYS, 2012. The area mainly locates within 34.5°–36.5°N, 122°–124.5°E, showing thick in the north and west and thin in the south and east with a ‘┌’ shape. The maximum thickness is up to 11 m. Meanwhile, there appears a weak deposition belt in the transition zone between the central South Yellow Sea muddy area and the slope deposit body surrounding Shandong Peninsula. In this paper, a numerical simulation under wind‐driven circulation in winter is established to study the dispersal and depositional processes of the suspended sediment. Studies show that the presence of a weak‐current‐low‐energy area by the tide is the primary factor to control the muddy area in central South Yellow Sea with similar results to previous research, but we find that the sediment is transported by the Yellow Sea Warm Current in winter. In winter, the Yellow Sea Warm Current can carry the southern sediment into here and we believe that it is the main driving force to transport sediment into the muddy area. The weak deposit band of the simulation result and measurement matched well; it is controlled by the shear front of the Yellow Sea Warm Current and the Yellow Sea Coastal Current. The shear front plays the role of a ‘water barrier’ to prevent the sediment carried by the Yellow Sea Coastal Current spreading directly to the muddy area and the sediment carried by the Yellow Sea Warm Current spreading to the coastal zone, so the weak deposit band arose. Copyright © 2016 John Wiley & Sons, Ltd.