Interannual changes of sea level in the two regions of East China Sea and different responses to ENSO

Abstract

Sea level changes in the two regions of the East China, separated by 30°N, were investigated based on the data of sea level anomalies (SLA) from Oct, 1992 to May, 2007. In the past 14 years, the rising rates have reached to 0.338 and 0.237 cm/yr in the two regions of East China Sea, respectively. The magnitudes of SLA increase or decrease in the East China Sea related to ENSO events are ± 2 cm. Interannual components of SOI and SLA are positively correlated in the Southern East China Sea (SECS), while with completely opposite phase in the Yangtze River Estuary and its adjacent sea (YRE), both significant at the 95% confidence level. This implies that the interannual changes of sea level in the East China Sea are dominated by ENSO events, and the dynamical mechanism between ENSO events and SLA in the two regions differs from each other. Wind stresses in the two regions have a strong response to ENSO events but opposite phase relationship with SOI, and local winds in the direction of 60° and 25° east by south over the YRE and SECS respectively affect the interannual changes of SLA the most strongest (both significant with anti-phase relationship at the 95% confidence level). The divergence zone in the East China Sea is wiggling from 30°N to 37°N. This change affects the wind field of the East China Sea strongly through atmospheric circulation, and in return makes the wind stress anomalies and SLA in the two regions response differently to ENSO events. To sum up, both ENSO and wind stress make contribution to the sea-level change over the East China Sea. Sea surface wind responds well to ENSO, indicating that ENSO could affect the sea level of the East China Sea through the mechanism of wind stress transfer. Because the local wind fields are closely related to the atmospheric circulation, the response of SLA to ENSO events is related to the location of divergence zone of atmospheric circulation over the East China Sea.