Spatio-Temporal Variability of Sea Level in the East China Sea

The spatio-temporal variability of sea level in the East China Sea (ECS) was investigated based on satellite altimeter data and tide gauge data. The sea level in the ECS has strong seasonal variations, being highest in autumn and lowest in spring. The seasonal variability is also highly variable in space. Affected by the East Asian monsoon, the sea level is higher in the north than that in the south, with its peak located near the Yangtze River estuary, especially in summer and autumn. In the past 50 years, the rate of the sea level rise near the Yangtze River Delta has been 5.45 mm/a, 1.5 times as high as the mean rate of the ECS. Therefore, the Yangtze River Delta, especially the Shanghai region, is more vulnerable to sea level rise in September and October. Monthly peak rate of the ECS is higher than the corresponding monthly average rate, with the biggest differences in March, April and October. The annual peak rate of ECS in autumn is 5.07mm/a, 1.4 times greater than the annual average rate, so more emphasis should be paid to the study of the sea-level peak to reduce the risk in coastal areas. Sea level change of the ECS has multi-scale cycle characteristics, where the annual sea level cycle is influenced by the runoff of Yangtze River and Kuroshio, while the seasonal variation characteristics are caused by strong seasonal change in sea level variation. The 30-month cycle is related to quail-biennial oscillation (QBO), the 134-month (about 11 years) cycle is the same as the sunspot activity cycle, and the 230-month (about 19 years) cycle corresponds to the moon's declination cycle (18.6 years). In the next decade, the sea level of the ECS is expected to continuously rise. We predicted that the next sea level peak period in the ECS will be around 2025.