Study Of Sea Level Change Over The South China Sea During 1993-2015

Sea level change(SLA) is a fundamental quantity for the study the global changes, and its trend and period also plays a key role in hotspot issues both abroad and at home. With the satellite altimetry technology continues to develop, Topex/Poseidon and its subsequent satellite Jason-1 and Jason-2 have a provided 23 years continuous altimeter data from 1993 to 2015 for studying SLA in South China Sea. The oceanic mass change (EWH) inverted by GRACE satellite data during 2003-2015, the oceanic evaporation trend analyzed by oceanic evaporation data during 1993-2015, and thermosteric sea level (TSSL)variation calculated using the temperature and salinity data during 2004-2015, have played significant roles on the average rate of sea level rise in South China Sea.Study of SLA based on altimeter data. The average rate of sea level rise resulted by from Topex/poseidon and its subsequent satellite Jason-1 and Jason-2 data show 5.81mm/yr from 1993 to 2015 and 1.61mm/yr from 2004 to 2015. The spatial irregular distribution of sea level change trend is high in the middle and low on all sides, and the average rate of SLA has different change trend during 1-12 month. Wavelet analysis is used to get period feature of the average sea level changes, found that the most significant is 1 -year period.Study of the oceanic evaporation variation based on evaporation data. The average rate of the oceanic evaporation rise is 2.87mm/yr from 1993 to 2015, which has indirectly effect on the average sea level change in South China Sea.The period of oceanic evaporation change calculated by spectral analysis and wavelet analysis also show 1- year period,which strongly consists with the period of SLA in South China sea.Study of EWH based on GRACE satellite data. The averge rate of EWH inverted by GRACE satellite data is 0.36mm/yr during 2003-2015.Compared with the rate of 1.61mm/yr of SLA, the values of EWH is obviously small. Through studying the spatial distribution of the average rate, the result indicated that there has been rising trend in northeast area and downward trend in southwest of South China sea. In addition, the spatial distribution of the rate of EWH from January to December is analyzed, we found that the trend is consisten with the trend of SLA based on satellite altimetry data, especially the same change cycle.Study of TSSL based on ocean temperture data and salinity data.The average rate of TSSL is 1.45mm/yr, which has contribution of 90%to SLA.Using Pearson correlation analysis, the result show that the correlation coefficient of EWH and SLA reach 0.584, and correlation coefficient between .evaporation change and SLA was 0.504.