Influence of ENSO on the variation of annual sea level cycle in the South China Sea

The variability of the annual sea level cycle in the South China Sea (SCS) has been explored based on tide gauge data, satellite altimetry data and Ocean General Circulation Model (OGCM) outputs. This variability has the potential to increase or decrease the flooding risk in the SCS coastal regions. The cyclostationary empirical orthogonal function (CSEOF) decompositions of the three data sets demonstrate consistent annual sea level fluctuations which are related to ENSO (El Niño-Southern Oscillation) variability. In particular, a significant reduction in the strength of the annual cycle is observed during the 1997-1998 El Niño event. The spatial variability of the annual cycle in the region as computed from the satellite altimetry and OGCM show excellent agreement, while the CSEOF analysis also captures the temporal and spatial distribution characteristics of the ENSO signal. As a secondary result, a drop in the strength of the annual sea level cycle is observed from tide gauge data resulting from the Sumatra-Andaman Earthquake event in 2004.