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Bottom mounted platforms equipped with current profilers/meters, temperature/salinity and turbidity sensors were deployed for about 10 days in August 2017 over an elongated deposit off the coast of Shandong Peninsula, in order to monitor the hydrodynamics and sediment processes in the bottom boundary layer. In total, semidiurnal barotropic tides dominate the measured currents, accounting for 90% of total variance. However, in the cross-shore direction, greater variance is associated with the semidiurnal internal tidal currents than the semidiurnal barotropic currents. Both the Empirical Orthogonal Functions and normal mode analysis demonstrate that the baroclinic velocity is dominated by the mode-1 internal tides, i.e. the current has a vertical shear with strong opposite flows near the surface and bottom while weak in the middle. Although the bottom slope is subcritical in most area of the deposit, the ratio between the bottom slope and the slope of internal tide characteristics is greater than 0.5, suitable for local internal tide generation. The internal tides generated from the deposit are especially significant considering that the shelf of the Yellow Sea is usually broad and flat. The quantitative estimation of the water column mixing indicate that the bottom dissipation induced by the barotropic tides (6.44ⅹ10−4 m3 s−3) is greater than the internal tides (−0.95ⅹ10−4 m3 s−3), and the total dissipation rate due to bottom drag is 5.49ⅹ10−4 m3 s−3, which is much greater than the interior one due to internal tides (2.69ⅹ10−4 m3 s−3). The internal tidal current alone is not energetic enough to resuspend the local fine-grained sediments. However, in the cross-shore direction, the sediment flux due to internal tides is twice as much as the barotropic component, resulting in a net onshore sediment flux, thus highlighting the advection effect of internal tides in the coastal mass transport. • This investigation is the first to quantify the semidiurnal-band characteristics of baroclinic tidal currents and evaluate the effect of the internal tides to sediment resuspension and transport in the region of a unique elongated mud deposit off the coast of Shandong peninsula. • Mode-1 semidiurnal internal tides, the dominant baroclinic motion, is believed to be related to the steep topography of the deposit and enhanced stratification in summer. • The near-bed stress induced by internal tides is not strong enough to suspend sediments, but its contribution to sediment transport due to advection cannot be ignored. [ABSTRACT FROM AUTHOR]

This paper investigates sediment trapping in coastal embayments during summer seasons based on observation data obtained from two instrumented tripods that were placed at the mouth of Weihai Bay on north coast of Shandong Peninsula, China, over a 15-day period between 5 and August 20, 2018. The data consisted of time series of water depths, current profiles, wave parameters, near-bed flow velocities, turbidity, water salinity and temperature. Distributions of suspended sediment concentration (SSC) and water temperature in the bay and adjacent sea areas were also investigated at 87 grid stations from July 31 to August 4, 2018. From these data the bed shear stresses, residual currents and suspended sediment fluxes (SSF) were calculated. The results indicated that the variability in the SSC at the northern mouth was mainly controlled by local sediment resuspension while at the southern mouth horizontal advection due to the SSC gradient was the dominant mechanism. To identify the main drivers of the sediment transport, the SSF was analyzed using the decomposition method. The seaward advective transport due to residual flow and landward tidal pumping effect dominated the total near-bed sediment transport at the northern and southern mouths, respectively. Therefore, trapping processes occurred mainly through the southern mouth. The suspended sediment fluxes (SSF) during neap and spring tides at the southern mouth were 0.053 and 0.321 g m−2 s−1, respectively, while during moderate wave conditions (H s > 0.8 m), the SSF was two times larger than the spring tide. In summer, the fine-grained sediments trapped in the bay were mainly derived from resuspension off the eastern tip of the Shandong Peninsula and thus is indirectly from the Yellow River. During such sediment transport and trapping processes, upwelling and winds can also play important roles. • SSC variations at the northern and southern bay mouth were controlled by local resuspension and horizontal advection. • Trapping occurred mainly through the southern mouth via tidal pumping as the SSC gradient dominated the net sediment flux. • Sediments trapped in the bay were mainly derived from resuspension off the eastern tip of the Shandong Peninsula. [ABSTRACT FROM AUTHOR]