Interannual Sea Level Variability In The Japan/East Sea And Its Response To ENSO

Comparing with the South China Sea (SCS), this study makes some investigations on the interannual variability of the sea level and thermosteric sea level in the Japan/East Sea (JES) and its response to ENSO, using a variety of mathematical methods, include the filter method, the correlative analysis, Empirical Orthogonal Function (EOF) analysis, regression analysis, the wavelet transform and wavelet analysis method. The possible physical mechanism and characteristics of the sea level interannual variability in the Japan/East Sea (JES) are studied.The thermosteric sea level anomalies from 1945.01 through 2005.12 obtained by using the global ocean temperature data sets recently published (Ishii et al.,2003, 2006) are used to investigate the interannual variability of sea level in the South China Sea (SCS) and Japan/East Sea (JES) and its response to El Nino and Southern Oscillation (ENSO). Both the interannual variations of the sea level and the thermosteric sea level obtained from reanalyzed data are closely related to ENSO. As a result, one important consequence is that the sea level trends are mainly caused by thermal expansion. The sea surface temperature anomalies and the seawater temperature anomalies in the layers deeper than 125m have inverse response to ENSO in the SCS. The whole regional thermosteric sea level trends are not stationary on ENSO time scales in the JES. An'enigma'that the correlation between sea level variability and ENSO during the period 1976-2005 is inconsistent with that during the period 1945-1975 in the Japan/East Sea is revealed. The thermosteric sea-level trends and the Southern Oscillation Index (SOI) suggested a strong negative correlation during the period 1976-2005, whereas it appeared to be a weak relatively positive correlation during the period 1945-1975 in the Japan/East Sea. Analyses based on 'Empirical Orthogonal Function'show that the interannual variability of the thermosteric sea-level during the period 1976-2005 is dominated by the signatures of ENSO. The technique of wavelet coherence analysis is introduced and used to explore relationships between thermosteric sea-level in the Japan/East Sea and ENSO. The thermosteric sea-level and the Southern Oscillation Index (SOI) show significant coherence on ENSO time scales during the period 1976-2005. The current fields and wind stress fields obtained by using the SODA (Simple Ocean Data Assimilation) data, and the precipitation obtained by using the CMAP (CPC Merged Analysis of Precipitation) data, are used to investigate the possible physical mechanism of interannual variability of sea level in the Japan/East Sea (JES).