Study On Mass Transport Induced By Coastal Trapped Waves Along The Coast Of East China Sea

The wide continental shelf of the East China Sea (ECS) is ecologically productive, many dynamical phenomena occur in the coastal ocean over the continental shelf. Mass transport nearshore is important due to its role in the transport of nutrients, larvae, sediments, and pollutants. Meanwhile, coastally trapped waves (CTWs) are one of the primary factors that modify the near-shore currents over the shelf and shelf slope region, and CTWs play an important role in transporting mass and exchanges over the shelf. However, the contribution of CTWs to the mass transport is presently unknown, the impact of wind-driven CTWs on the transport are firstly investigated in the ECS starting from theory.Firstly, deducing the CTWs theory which agrees with the special topography of this area. Secondly, the wind-driven CTWs are applied to the ECS under idealized wind stress on the order of 10-1 N m-2, and the impact of wind-driven CTWs on the structure of the cross-shelf transport are investigated. The cross-shelf currents are divided into four terms: the geostrophic balance (GB) term, the second-order wave(SOW) term, the bottom friction (BF) term and Ekman (EK) term, as well as three modes: the Kelvin wave (KW) mode, the first shelf wave (SW1) mode and the second shelf wave (SW2) mode. For the four terms, the effect of the GB and EK term is continual, while that of the BF term is confined to 60-240 km offshore, and the contribution of the SOW term can be ignored; For the three modes, the KW and SW1 mode are dominant in cross-shelf transport. At the same time, the bottom friction plays an important role in the study of the mechanism of cross-shelf transport. With the increase of linear bottom friction coefficient, the cross-shelf transport declines with distance with the slope becoming more uniform.Because the wind-driven CTWs model in the ECS is quite ideal, the next step is to analyze alongshore transport and cross-shelf transport using Regional Ocean Modeling System (ROMS) data. The results show that there are CTWs propagating from the coast of Shandong Province to Jiangsu Province with the period of these wave are about 2.7?4.2 and 10.4 day respectively, and the fastest phase speed of 10.2 ms-1. According to the selected alongshore profile and cross-shelf profile at 50m isobaths, the alongshore transport and cross-shelf transport are calculated, then using Ensemble Empirical Mode Decomposition (EEMD) decomposes the mass transport induced by CTWs with periods of about 2.7?4.2 and 10.4 day, and the result shows that the contribution of CTWs to alongshore transport is much more than that to cross-shelf transport.