Non-seasonal sea level variations in the Korea Strait and regional atmospheric conditions

To investigate dominant sea level variations in the Korea Strait (KS) and to find their responsible factors, Empirical Orthogonal Function (EOF) analysis was performed on the non-seasonal components of sea level, wind, and sea level pressure data from 1993 to 2014. The non-seasonal sea level variation accounts for 20% of the total sea level variations in the KS. The first EOF mode of the sea level explains 63.8% of the total variance and represents strait-wide simultaneous sea level oscillations. EOF analysis on the surface wind data over the KS and the East China Sea was performed and the first EOF of winds, explaining 49.5% of the total variance, represents the strength of the northeasterly wind. The amplitude time series of the first EOF s from wind and sea level data has correlation coefficients (r) of 0.48. The sea level and wind data have common spectral peaks at periods of 5.1 and 10.2 months. Variance and the first EOF of the steric height in the KS are relatively high around Jeju Island while they are small near the south coast of Korea. Correlation between the amplitude time series of sea level and steric height first modes is low (r = 0.20). The basin-wide simultaneous sea level variations with intra-seasonal and interannual periods in the KS are found to be modulated by variations in the regional surface winds and sea level pressure patterns over the East China Sea and the KS rather than by changes in local steric height.