| Summary: | 碩士 === 國立臺灣大學 === 地質科學研究所 === 95 === Monthly-resolution geochemical proxies, such as 18 O, 13 C, Sr/Ca, and Ba/Ca, in a living Porites coral head, collected from Son Tra Island, central Vietnam (162''59.4", 108''57.1"), was used to quantita ?? tively reconstruct the local sea surface temperature (SST), the annual dynamics of the East Asian winter monsoon (EAWM), as well as the monthly change of regional hydrological conditions. By comparing the 1/4-century geochemical data, five features are exhibited. (1) The coral Sr/Ca-inferred summer SSTs correspond well with the 1x 1instrumental data to ?? demonstrate the validity of coral Sr thermometry. (2) The winter surface pressure difference, between the southern South China Sea (SCS) (0-10 癗 , 105-115 癊 ) and the northern SCS (22.5-32.5 癗 , 112-122 癊 ), matches coral winter SST data, indicating that the coral-inferred thermal extremes can be employed to retrieve the EAWM 18 O residual ( 18 O) suggests a 2-4-psu seasonal salinity change between dry and wet seasons. (4) The monthly 18 O data show that the regional rainy season is from late summer to winter which is consistent with the meteorological record. This phenomenon is also observed in seasonal variability of Ba/Ca record. (5) The high Ba/Ca background level of 10 mol/mol in 1992-2004, 2-3 times larger than the averaged value of 4 mol/mol in 1978-1992, suggests an enhanced terrestrial sediment discharge into the marginal sea over the past 10 years. Ba records reveal an economical impact on hydrological change since the Vietnam War. Our results show that the Son Tra coral geochemical records can be used as proxies of climate and environment changes and of human activity.
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