An exploratory model study of sediment transport sources and deposits in the Bohai Sea, Yellow Sea, and East China Sea

Abstract

A regional ocean circulation model (ROMS) is used to simulate the Chinese land‐derived sediment transport in the Bohai Sea, Yellow Sea, and East China Sea (BYECS). The model includes the effect of currents, tides, and waves on the sediment transport and is used to study the pathway and dynamic mechanisms of the fine‐grain sediment transport from the Huanghe River (Yellow River), the Old Huanghe Delta, and the Changjiang River (Yangtze River) in the BYECS. The seasonal variability of the sediment transport in the BYECS and the sources of the Yellow Sea Trough mud patch, the mud patch southwest of Cheju Island, the mud patch offshore from the Zhejiang and Fujian provinces and the Okinawa Trough mud patch are discussed. The results show that the Huanghe River sediment can be transported to the Yellow Sea Trough, but little makes it to the outer shelf while the Old Huanghe Delta sediment is mainly transported to the Yellow Sea Trough. Most of the sediment from the Changjiang River mouth is carried to the mud patch off the coast of the Zhejiang and Fujian provinces but with part of this sediment also transported to the Yellow Sea Trough. The model shows that it is difficult to transport land‐derived sediment to the Okinawa Trough mud patch under normal conditions. The model also has difficulty accounting for the deposition of sediment in the region to the southwest of Cheju Island and offshore from the Zhejiang and Fujian provinces, an issue requiring further study.

Morphodynamics at the Coastal Zone in the Laizhou Bay, Bohai Sea

“…This decrease makes sea level change and wind-wave dynamics become increasingly important for the coastal development compared to fluviatile factors. At the same time the tide plays the dominant role in transporting sediments out of the sheltered embayment system to deeper shelf and the Yellow Sea ( Bian et al, 2013;Lu et al, 2013) . Numerical studies confirm the interpretation and estimation of Yang and Liu (2007) that along shelf sediment transport delivered by Yellow River formed clinoform deposits along the eastern tip of Shandong Peninsula in the Yellow Sea during the last 7000 years.…”

Hydrography-Physical Description of the Bohai Sea

“…There are two amphidromic points of M 2 ( Figure 11a) : one is near the mouth of the Yellow River at the south-western coast, and the other one is located offshore of Qinhuangdao at the northwestern coast. The model simulated maximum amplitude of the M 2 tide is about 110 cm in Liaodong Bay and 70 cm in Bohai Bay which are about 10% smaller than the M 2 amplitude calculated from TOPEX / Poseidon altimetry data and other model studies ( Bian et al, 2013;Huang et al, 1996;Pelling et al, 2013) .…”

“…In the surface layer, the Lagrangian residual currents form a clockwise flow in the Bohai Bay and the Liaodong Bay. In contrast, it flows north-eastwards into the Laizhou Bay and the central Bohai Sea with current speeds of 1~5 cm / s. In the bottom layer strong residual currents flow north-eastwards into the Liaodong Bay showing current speeds between 1~5 cm / s. Bian et al (2013) It should be noticed that the Bohai Sea has experienced rapid coastline changes recently due to natural developments of the Yellow River delta and large-scale anthropogenic land reclamation which substantially alters the tidal dynamics of this area. A numerical tidal model showed that the M 2 tidal amplitudes have changed by up to 0． 2 m over the last three decades due to the rapid coastal development ( Pelling et al, 2013 ) , and another numerical model showed that besides tidal amplitudes, the tidal energy flux is also affected by the land reclamation in the Bohai Sea ( Song et al, 2013) .…”

“…Guan (1994) The circulation system in the Bohai Sea ( Figure 4) shows that the main inflow occurs along the northern Bohai Strait by the intrusion of the Yellow Sea Warm Current ( YSWC) in winter. In the southern Bohai Strait, the Bohai Sea water flows out all the year ( Bian et al, 2013;Guan, 1994) . Altogether, the net transport through the Bohai Strait is a superposition of continental outflow and Yellow Sea inflow.…”

“…It is important to note, that the sediment transport budget finally determines the morphological changes in the Bohai Sea. Numerical studies of the sediment transport in the Bohai Sea ( Figure 13) showed that the sediments discharged by the Yellow River are transported to the north-western Bohai Sea due to the residual currents ( Bian et al, 2013;Jiang et al, 2004) . After 12 months, the Yellow River discharged sediments almost cover the whole Bohai Sea.…”