Progressive change of tidal wave characteristics from the eastern Yellow Sea to the Asan Bay, a strongly convergent bay in the west coast of Korea

Abstract

Although there have been studies on the tide in convergent bay (or estuary), the tide change in terms of phase speed, amplitude, and phase difference between elevation and tidal current from a coastal ocean to a convergent bay has not been clearly shown so far. This study systematically examines the change of tidal wave characteristics from the eastern Yellow Sea to the Asan Bay, a strongly convergent bay on the west coast of Korea, using observations and an analytical model. As the tidal wave propagates from the eastern Yellow Sea into the Asan Bay, the phase speed, amplitude, and phase difference between elevation and tidal current increase along the channel. Such a phenomenon represents a unique example of tide change from a coastal ocean to a convergent bay, indicating dominance of convergence over friction in the Asan Bay. Both analytically computed tidal amplitude and travelling time compare well with observations. In the Asan Bay, the influence of the reflected wave is only felt in the upper one fifth of the bay and is almost unperceivable in the rest of the bay. The analytical analyses presented in this paper are particularly useful for understanding the relative importance of channel convergence, bottom friction, and reflected wave on the tidal characteristics change along the channel and the proposed method could be applicable to other estuaries.