Park, S.J.; Choi, B.-J.; Sim, H.S., and Byun, D.-S., 2020. Arrival of long ocean waves and hourly sea level oscillations in Masan Bay, Korea on 19-22 March 2014. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1510–1514. Coconut Creek (Florida), ISSN 0749-0208.
Calmness and predictability of the sea level in a harbor are essential for safe shipping and cargo-loading on vessels. Masan Bay is an inner bay located on the south coast of Korea where the mean spring tidal range is 174 cm. It has been reported that sea level often fluctuates hourly in Masan Bay in addition to the effect of tides. The cause of the hourly sea level fluctuations have not been explained. The fluctuation periods are close to the natural resonant periods which are determined by the harbor geometry and depth. To find the generating sources of the hourly sea level fluctuations and to examine their characteristics, sea level data measured minutely at Masan harbor and the neighboring 11 tidal stations were analyzed. There were 42 events of long-period sea level oscillations with a maximum height of more than 40 cm in Masan Harbor from 2013 to 2017. Power spectral analysis on the sea level data shows the presence of high energy density in the periods ranging from 48 to 125 min at Masan and neighboring tidal stations. It was found that long ocean waves frequently propagate from the southwestern region of Korea Strait (KS) and enter Masan Bay. Time-lagged correlation analysis between the time series of sea level data along the south coast of Korea in March 2014 suggests that the long waves propagated from the southwestern KS to the eastern KS and entered Masan Bay. It took 2 h 27 min for the waves to propagate from Jeju Island in the southwestern KS to Masan Harbor. The estimated traveling speeds of the long waves using time-lagged correlation analysis were similar to the shallow water wave speed in the region. Oceanic processes that generate the propagating long ocean waves might be tsunami, seismic waves, meteotsunami or internal waves in the open ocean. The long wave events were not related to local winds or air pressure variations.