Numerical Simulation Of The Effect Of The Sea Level Variation On Tidal Wave In The East China Sea

With global warming, sea level rise is one of the typical characters of global change in recent dacades, and has become the focus of world attention. In addition, Sea level variation has the significant seasonal period. The sea level variation of both the long term and seasonal scale affects the tidal wave system. Such effect will be discussed in detail in this paper in the follwing aspect:the AVISO altimeter merged data from Oct.1992 to Nov.2007,is used to analyze the sea level variations of the East China Sea; ECOMSED model is used to simulate the tidal wave of the East China Sea; assuming the sea level change trend in future is the same as the calculated trend of the past 15 years,the tidal wave of 50 and 100 years in future is simulated,to analyze the effect of the sea level long term variation; the tidal wave in different seasons is also simnulated to annlyze the effect of the sea level seasonal variation.The analysis shows that the sea level in the East China Sea is relatively the highest in October and lowest in April, and the sea level change rate has obvious spatial distribution. The sea level of the East China Sea is totally ascending, only in the coastal regions of Zhejiang, Fujian, Xiamen, Taiwan Strait, Miyako Islands,Okinawa Island and the Japanese Sea is descending. The basic ascending rate is about 3～5mm/a, but in some coastal areas,up to 9mm/a, for example on the top of Bohai Bay.In the process of the sea-level long term variation, the tidal amplitude and the phase lag matains basically unchanged in the deep ocean, but change significantly in the shallow water. Semidiurnal tidal constituents vary more than that of diurnal tidal constituents.The amplitude of semidiurnal tidal constituents tends to increase in most regions while decrease in some region, for example,the mouth of Yangtze River, the areas where the amplitude increased lager in turn are Radiated Sandbank of the northern region of Jiangsu, Jiangjin Bay, Haizhou Bay, West Korea Bay and Liaodong Bay. The phase lag of semidiurnal tidal constituents tends to increase in the Bohai Sea, Yellow Sea, shallow waters of East China Sea, and derease only in the areas near the amphidromic points.The amplitude of diurnal tidal constituens tends to increase in the Bohai Sea, South Yellow Sea, northeast of the North Yellow Sea, coastal areas from the Southern part of Zhejiang to Fujian, while decrease in the other areas.The phase lag of diurnal tidal constituens tends to increase in the east area of the Bohai Strait and the eastern part of the South Yellow Sea and East China Sea. The amphidromic points of diurnal tidal constituens all tend to migrate to the southeast, and those of diurnal tidal constituens have no similar routine,but migrated more or less.Sea level variation of the seasonal scale makes tide wave system to behave some variation rule, including the amplitude and the phase lag. Compared to the annual tidal waves, the variety of the amplitude and phase lags in Winter and Spring is basically converse to that in Summer and Autumn. The amplitude of semidiurnal tidal constituents changes much higher than that of diurnal tidal constituents.The amplitude's annual range of M2 tial constituent is up to 5cm, and that of S2 tial constituent is up to 2cm.The amplitude of the diurnal constituents basically changes within lmm, and the annual range is less than 2mm.The phase lags changes a lot in the vicinity of the amphidromic points. While in the coastal region away from the amphidromic points, the amplitude's maximum change of semidiurnal tidal constituents is about 20,and that of diurnal tidal constituents is about 10.