Evaluation of sea level rise in Bohai Bay and associated responses

Tide gauge data from 1950 to 2015 are used to analyze sea level change, tidal change, return levels, and design tide levels under rising sea level scenarios in Bohai Bay. Results show the following: 1) Since 1950 sea levels in Bohai Bay show a significant rising trend of 3.3 mm per year. The speed has been particularly rapid in 1980-2015 at a rate of 4.7 mm per year. 2) Astronomical tides showed a clear long-term trend in 1950-2015. The amplitude and phase lag of the M2 tide constituent decreased at a rate of 0.21 cm per year and 0.11 degrees per year, respectively and the phase lag of K1 decreased at a rate of 0.09 degrees per year, whereas there was little change in its amplitude. The mean high and low tides increased at a rate of 0.08 and 0.52 cm per year, respectively, whereas the mean tidal range decreased at a rate of 0.44 cm per year. Results from numerical experiments show that local sea level rise plays an important role in the tidal dynamics change in Bohai Bay. 3) It is considered that the sea level return periods will decrease owing to the influence of sea level rise and land subsidence, therefore design tide level will change in relation to sea level rise. Therefore, the ability of seawalls to withstand water will diminish, and storm surge disasters will become more serious in the future.