SEASONAL VARIABILITY OF THE M(2) TIDE IN THE SEAS ADJACENT TO KOREA

Seasonal variability of the M2 tidal harmonic constants is revealed th rough analyses of monthly tidal data at 12 representative tidal statio ns in the seas adjacent to the Korean peninsula. The variability remai n systematic over the 9 years (1965-1973) of data analysis with a rang e comparable to that of the 18.6 year nodal modulation. Spatial inhomo geneity of the seasonal variability in the observed harmonic constants is found to exist. The largest seasonal variability in M2 appears in the stations located along the Korea Strait. This variability is not e xplained by the equilibrium theory of tides, and such a variability or irregularities in the harmonic constants are considered as either a n oise as done by Cartwright and Amin (1986), Deutsch Hydrography Zeitsc hrift, 39, 235-253, or a manifestation of frictional interaction as do ne by Godin and Gutierrez (1986) Continental Shelf Research, 5, 379-40 2 for the Bay of Fundy. Considering the opposite relation between mont hly mean sea level differences in Izuhara-Pusan section and tidal char acteristics in the Korea Strait, it is hypothesized that the interacti on between the predominant tidal currents and oceanic currents varying with the seasons might be the main cause of the observed temporal var iability in the M2 tide. The nonlinear effect of the Kuroshio is inves tigated along the shelf break region through scale analyses, which sho w that the presence of a mean current increases the non-linear terms i n the momentum balance by about one order of magnitude. The seasonally different damping effect of the Tsushima Current to the M2 tide is al so discussed to explain the process of dominant seasonal variability a long the Korea Strait based on the actual current data, but further th orough investigation, considering the advection effect of the mean cur rent, is required to investigate the associated dynamics more complete ly.