The seasonal sea level variability and the long term trend of the sea level in the China Seas is investigated based on the monthly mean sea level data at 48 long term tide stations. Results show the average rising rate of all the stations is 2.3mm/a. The rising rate of the sea level in the north area is a little larger than the south area, and large rising rate appears on the island or at the big river mouth. The annual range of the sea level along the coast of China seas shows larger values in the north than in the south. The months when the highest or lowest sea levels occur in the south area lag the north area. River runoff can influence the annual range of the nearby sea level prominently. Monsoon, sea surface air pressure and SST are three important factors that cause the sea level variation along the coast of the China seas.
Over the past 20th century, the global mean sea level has risen about 10-25cm with a most likely value of 18cm (Gornitz,1995; Warrick et al., 1996), corresponding to a rate of about 2mm/a. The thermal expansion of the upper ocean and the melting of mountain glaciers associated with global mean surface temperature rising are the most important contributors. For the low-lying coastal areas, a small rising rate of the sea level may cause profound economic and social burden, as sea level rise will significantly aggravate the disaster of storms and marine erosions. And for the coastal areas, it is not the absolute but relative sea level that is concerned most. In recent years, more and more research reveals a rising sea level along the coast of China seas on the background of the global mean sea level rise.
