Tidal characteristics change for 50 years around the Jeju Island in the South Sea of Korea

Physical environment is changing in the Pacific Ocean and it is well-known that the internal waves develop and propagate in the Pacific Ocean. Since the changing physical environment of the Pacific Ocean may influence the tidal phenomena in the coastal ocean, it will be worthwhile to know first how the tidal characteristics in its marginal seas changes. In this study we examine the long-term tidal characteristics change at the northern and southern coasts of the Jeju Island located in the South Sea of Korea which is open to the North Pacific Ocean through the East China Sea. The semidiurnal tides, M
₂
and S
₂
observed at the northern (JJ) and southern (SGP) coasts of the Jeju Island in the South Sea of Korea show the decreasing trend of amplitudes and the increasing trend of the phases. On the other hand, the diurnal tides, K
₁
and O
₁
at JJ show minimum amplitudes in 1977 and then show the increasing trend. The amplitude of O
₁
at SGP also shows the increasing trend. These results may reflect the changing physical environment of the Pacific Ocean. The various factors such as changing stratification, eddy viscosity, mean current and meteorological forcing as well as nodal variations may be involved in these changes observed in the South Sea of Korea.