Storm-Generated Surface Waves and Sediment Resuspension in the East China and Yellow Seas

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  • 1 Coastal and Ocean Fluid Dynamics Laboratory, Ocean Engineering Department, Woods Hole Oceanographic Institution
  • | 2 Department of Physical Oceanography, Woods Hole Oceanographic Institution
  • | 3 Coastal and Ocean Fluid Dynamics Laboratory, Ocean Engineering Department Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
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Abstract

Surface winds derived from atmospheric pressure fields are used as input to a finite-depth wind-wave model to predict the sea state during a cold air frontal passage over the Yellow and East China Seas, which occurred 15–18 November 1983. The predicted maximum wave-stress field near the bottom is used to examine the concept of turbulent wave intensities causing sediment resuspension. The temporal variability of the wave field at three sites is used to illustrate the dependence of the bottom response on depth within the Yellow Sea. Maps of the temporal and spatial distribution of index for initiation of sediment movement are computed for different noncohesive sediment materials during this storm period and compared to sedimentological results for this region.

This study demonstrates that wave action is a mechanism which can significantly influence the sediment transport pattern induced by the regional circulation existing in this marginal sea. The results also identify regions where winter storm-generated surface waves are too weak to affect bottom sediments. Although the spatial variability of sediment resuspension depends on sea state and sediment material, the predicted wave-induced bottom shear stresses during a characteristic winter storm show that fine-grained material can be re-suspended as far out as the 100 m isobath in the East China Sea. Temporal maps of the index of sediment movement further show that the critical shear stress is exceeded for silty sand over large regions of the East China Sea during the duration of the storm studied.

These numerical simulation results suggest that the present-day distribution of sediments in the Yellow and East China Seas is in part a direct consequence of storm-generated surface waves during the winter season. The numerical model results further suggest that erosion of sand along the Chinese and Korean coasts is largely determined by surface wave action. Furthermore, the present-day mud patch south of Cheju Island appears to be a consequence of the circulation pattern in the Yellow and East China Seas and the southeastward decrease in wave and tidal bottom stress.

Abstract

Surface winds derived from atmospheric pressure fields are used as input to a finite-depth wind-wave model to predict the sea state during a cold air frontal passage over the Yellow and East China Seas, which occurred 15–18 November 1983. The predicted maximum wave-stress field near the bottom is used to examine the concept of turbulent wave intensities causing sediment resuspension. The temporal variability of the wave field at three sites is used to illustrate the dependence of the bottom response on depth within the Yellow Sea. Maps of the temporal and spatial distribution of index for initiation of sediment movement are computed for different noncohesive sediment materials during this storm period and compared to sedimentological results for this region.

This study demonstrates that wave action is a mechanism which can significantly influence the sediment transport pattern induced by the regional circulation existing in this marginal sea. The results also identify regions where winter storm-generated surface waves are too weak to affect bottom sediments. Although the spatial variability of sediment resuspension depends on sea state and sediment material, the predicted wave-induced bottom shear stresses during a characteristic winter storm show that fine-grained material can be re-suspended as far out as the 100 m isobath in the East China Sea. Temporal maps of the index of sediment movement further show that the critical shear stress is exceeded for silty sand over large regions of the East China Sea during the duration of the storm studied.

These numerical simulation results suggest that the present-day distribution of sediments in the Yellow and East China Seas is in part a direct consequence of storm-generated surface waves during the winter season. The numerical model results further suggest that erosion of sand along the Chinese and Korean coasts is largely determined by surface wave action. Furthermore, the present-day mud patch south of Cheju Island appears to be a consequence of the circulation pattern in the Yellow and East China Seas and the southeastward decrease in wave and tidal bottom stress.

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