The Impact of Winter Storms on Sediment Transport Through a Narrow Strait, Bohai, China

• Published in: Journal of geophysical research. Oceans 2020-06, Vol.125 (6), p.n/a
• Main Authors: Wang, Chenghao, Liu, Zhiqiang, Harris, Courtney K., Wu, Xiao, Wang, Houjie, Bian, Changwei, Bi, Naishuang, Duan, Haiqin, Xu, Jingping
• Format: Article
• Language: English
• Subjects: Bohai Strait; Coastal currents; Coastal sediments; coastal trapped waves; Diagnostic systems; Doppler sonar; exchange flow; Exchanging; Fluctuations; Fluvial sediments; Fluxes; Geophysics; Inflow; Mathematical models; Numerical models; Outflow; Profilers; Resuspension; Rivers; Sediment; Sediment concentration; Sediment dynamics; sediment flux; Sediment transport; Sediments; Storms; Straits; Suspended sediments; Tidal currents; Transport processes; Trapped waves; Wind; Winds; Winter; Winter storms
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2020JC016069

The Yellow River is one of the most significant sources of terrestrial sediment to the global seas, and the Bohai Strait is the only pathway that delivers Yellow River‐derived sediments from the shallow Bohai Sea to the Yellow Sea. To investigate sediment transport processes through the strait under the influence of storms (strong northerly winds) that frequently occur in winter, we deployed two sets of observing platforms equipped with Acoustic Doppler Current Profilers (ADCP) and a suite of other sensors in the strait in January 2018. Aided by a system of high‐resolution models, we reconstructed sediment dynamics in response to the strong northerly wind of a winter storm. Model results show that the instantaneous suspended sediment flux (SSF) is highly aligned with tidal currents, while the net sediment flux has a clear dependence on variations in exchange flow and sediment resuspension. Enhanced coastal currents, intensified wave motions, and higher suspended sediment concentrations indicate that the through‐strait sediment flux during outflows is greater than during inflow conditions. Such SSF asymmetries are believed responsible for the net sediment export through the Bohai Strait in wintertime. Diagnostic analyses provided insights into the dynamic mechanisms of exchange flow variations influenced by both the strong northerly winds and the wind‐triggered coastal trapped waves in the shallow, narrow strait via geostrophic effects. This study highlights the importance of storm‐induced horizontal exchange processes in a coupled bay‐shelf system. Plain Language Summary The aim of this study is to characterize the dominant processes that control net wintertime sediment fluxes through a narrow strait. Flows, waves, and sediment concentration were measured in the strait during a winter storm. A well‐validated model showed that wintertime flows in the strait are dominated by alternating, strait‐wide inflow and outflow. Occasionally, however, inflows and outflows are concurrent over different sections of the strait. Based on a numerical model, our calculations of sediment flux for the entire winter revealed that large net sediment flux occurred when both winds and waves were strong. These results provide a better understanding of how sediment transport in a bay‐shelf system has driven by both local and remote forcing mechanisms. Key Points Winter storms can generate low‐frequency oscillations of barotropic flows accompanied by sea surface height fluctuations