Reconstruction Of Typhoon Event In Xincun Lagoon,Hainan Province In The Past 200 Years

Typhoon with the strong winds,heavy rains and storm surges is one of the major natural disasters in China.It has caused huge economic losses and casualties to the coastal areas.In the context of global warming,typhoon activity become more abnormal and more difficult to predict.Therefore,the study of typhoon history and its laws and mechanisms has important practical significance in predicting frequency,intensity and path of future typhoon and reducing the huge losses caused by typhoon.However,the detailed typhoon recording by satellite measurements is relatively short.The long-term typhoon historical archives are scattered and discontinuous,which is not conducive to the prediction of typhoon.The study of typhoons requires longer and more continuous record urgently.Therefore,the lagoon sediments of Hainan Island,which are often affected by typhoons,were studied.The grain size,TOC,TN,C/N ratio,?13C and ?15N of 144 samples were analyzed to identify the storm deposits.The sequence of typhoon activity of Xincun Lagoon in the past 200 years was established by combining the multi-index cross-validation verification with the typhoon historical document records.The main results are as follows:1.The mean sedimentation rate was 0.34 cm/a in Core LSXC-S1.2.Analysis of grain size data shows that the composition of sediments in the central part of Xincun Lagoon is dominated by silt.The end-member modeling analysis was performed on the grain size data of 144 samples and the data was decomposed into four end members(EM1,EM2,EM3,EM4).The total explanatory amount of the model is 99.5%,and the interpretation amounts of EM1,EM2,EM3,and EM4 for the overall samples are 7.73%,14.84%,70.75%,and 6.67%,respectively.Through the analysis of the characteristic curve of the end members,it is considered that EM1 represents the deposition of dust particles after long-distance migration or the deposition by the exogenous stream;EM2 represents the deposition of surface runoff by rainfall erosion;EM3 represents the resuspended deposition carried by tidal current and waves;EM4 represents the strong hydrodynamic event deposition caused by typhoon activity.3.By analyzing the geochemical proxies(TOC,TN,C/N ratio,?13C and ?15N)of 144 samples,it was found that the Xincun lagoon has been significantly affected by marine materials since 1920.The impact of the sea on the Xincun Lagoon has intensified by the stronger wind,waves and typhoons.It also shows that the lagoon has been significantly affected by human activities in the past decade.4.The storm deposition layers in Core LSXC-S1 was identified by studying the changes of grain size(EM4,sorting factor)and geochemical proxies(TOC,TN,C/N ratio,?13C and ?15N).And 22 typhoon periods from 1806 to 2016 were reconstructed.During the period from 1855 to 1990 and 1955 to 1986,it was the low tide period of the typhoon.The frequency and intensity of the typhoon that affecting the Xincun Lagoon increased significantly after 1900.