Analysis of temporal and spatial characteristics of sea surface temperature variabilities over the past 34years in coral reef areas of the South China Sea
A monthly sea surface temperature(SST)data from 1982to 2015 of the South China Sea(SCS)was extracted based on the NOAA OISST data set in this study.First count up the SST at the Dongsha,Xisha and Nansha reef islands on time scale.Then the empirical orthogonal function(EOF)method was applied to the monthly anomaly field of the data set to analyze the characteristics of the yearly spatial and temporal variabilities of the SCS SST distribution.The study showed as follows:(1)The SST warming trends were differed at different reef areas.The rising trend of SST in the Dongsha reef area was the most significant (about 0.216℃/(10a)).The following trends were 0.18℃/(10a)at Xisha reef area and 0.096℃/(10a) at Nansha reef area,respectively;(2)The SST in the Xisha and Nansha reef areas were in the optimum growth temperature of hermatypic corals in the whole year.There were about 4months lower SST for hermatypic corals in the Dongsha reef area.The hottest month were focus on July(Dongsha),June(Xisha)and May(Nansha),respectively;(3)The first mode of EOF showed that SST over the SCS was spatially in phase and declined from northwest to southeast.That was Dongsha>Xisha>Nansha;(4)The first mode temporal distribution of EOF showed that the variation of SST in the SCS was related to the El Nino.The correlation analysis between SSTA over the SCS and the index of Nino3.4showed that the average incidence was 0.655,and the highest correlation degree was 0.723.The SSTA over the SCS was lag of Nino3.4about 7-8months.In summary,under the background of global warming,the change of SST in the SCS is not only affected by the El Nino,but the continued rising is quietly threaten the growth of corals.