The Recent Fifty Years High-resolution Climate Of Nansha Islands Recorded In Reef Coral

Directed by Pro f Liu TungsheIlg, Zheng hongllan, Zhao Huanting, Liao WeikuaA 50-year Porites lutea core from Nansha Islands (9~。 33' N, 112~。 54' E)was analyzed for δ~18 O and δ~13C for two aims. First, we hope to find and set up someformula between δ~18O (δ~13C ) and environmental parameters, such as thermometerreadings, so that we can reconstruct historical environment of this area. Second, wehope to understand the climate changing process during the past fifty years of thisarea and its relation to the global change.The study indicated that the reef coral δ~18O is not only a good sea surfacetemperature (SST) thermometer, but aIso a good air temperature thermometer It'sthe first report about coral δ~18O air temperature. With the two thermometers, wereconstructed the past fifty years seasonally and annually SST and air temperature ofNansha Islands, and found that there are 7y, l2-l3y and l5y temperature oscilIatedcycIes. During the past fifty years, the SST and air temperature of Nansha Islandsshow consistent warming trend to the middle and the north of the South China Sea,and the air temperature of wholly China. and the global SST and air temperature.The coral δ~13C can record temperature, sunshine, cloud amount and rainfall ofYongshu Reef. The reconstncted sunshine and cloud amount based on δ~13C indicatedthat the sunshine duration of Yongshu Reef show a decreasing trend, and the cloudamount show an increasing trend.The coral δ~18O and δ~13C of Nansha Islands can trace the El Nino events sincel95l. When the El Nino process goes through winter, the coral winter δ~18O is usuallycharacterized by a negative anomaIy. During the El Nino year from 1951 to 1972, thespring and annual coral δ~18O, as weII as coraI δ~13C almost show positive anomalies;and during the El Nino year since l972, the spring and annual coral δ~18O, as weIl as- lIcoral 6 l3C almost show negative anomalies.The coral winter 5l8O of Yongshu reef show a high correspondence to thesummer drought or flood condition of the middle and the lower reaches of theYangtze River. When the coral winter 6"O is towards loW the middle and the lowerreaches of the Yangtze River will have more rainfall. This teleconnection providesone go0d way in looking for the rule of drought or flood of Yangtze River. lt is alsothe first report about coral 61sO and its teleconnection with drought or floodconditions of the far away mainland.The groWth rate of POriles IlIIea in Nansha lslands shows positive correlation totemperature. The seawater 618O of the South China Sea shows significant correlationto latitude and salinity.The study aIso concludes that tl1e Nansha Islands coraI is a valuable source ofinfOrmation on global climate changes.