Vertical land movement over China coasts determined by tide gauge and satellite altimetric data

Sea level change (SLC) extracted from tide gauge data references to the benchmark fixed coastal land. Sea level change determined from satellite altimetric data references to ellipsoid with respect to the Earth’s mass center in a terrestrial reference frame. In order to study the vertical land movement over China coasts, we simultaneously process altimetric data of TOPEX/Poseidon (T/P), Jason-1 and Jason-2, and tide gauge data of 21 stations from 1993 to 2012. We use altimetric data in the tandem stages to correct biases point by point between T/P and Jason-1, Jason-1 and Jason-2 to get precise sea level changes over China seas. Monthly and yearly averaged sea level changes near the corresponding tide gauge stations are estimated from tide gauge data from University of Hawaii Sea Level Center (UHSLC) and Permanent Service for Mean Sea Level (PSMSL). Correlation coefficients between two time series of SLCs determined by 21 tide gauge stations and altimetry data near each station with the same time span are calculated. The result shows that there are 8 stations correlation coefficient between 0.6 and 0.9, 10 stations correlation coefficient between 0.3 and 0.6, and 3 stations correlation coefficient below 0.3 which indicate that SLCs from these two techniques have the identical trends. Differences of SLC rates determined from altimetry data and tide gauge data can stand for the vertical land movement over China coasts. Fifteen tide gauge stations were selected over China coast whose data integrities are high, time spans are long, and correlation coefficients with altimetry SLCs are greater than 0.4. Lands over China mainland coast sink except Laohutan and Shanwei in this study. The land coast sink ranges of China mainland is mostly from −0.05 to −0.58 cm/year but the most settlement takes place in Haikou which sink up to −1.71 cm/year. Laohutan and Shanwei stations rise at 0.3 and 0.72 cm/year, respectively. Lands over Taiwan Island and Hong Kong basically rise in these 20 years and the rise range is from 0.11 to 0.47 cm/year.