Assessment of coral skeletal oxygen and carbon isotope raitions from Ishigaki Island as environmental proxies
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The chemical and isotopic compositions of coral skeleton can be used as past climate proxies for tropic and subtropic regions. We have collected a coral core representing 170 years of continuous growth from Ishigaki Island, the Ryukyu archipelago, Japan and conducted detailed analysis of skeletal oxygen and carbon isotope ratios (δ18Oc and δ13Cc) for the upper portion of the sample. The isotope ratios, measured along the major growth axis of the coral skeleton, showed clear periodic variations. A significant linear correlation was found between δ18Oc and sea surface temperature (SST) at Ishigaki Port, especially in winter data. Thus, wintertime δ18Oc is a good proxy for winter SST. In contrast, no significant correlation was observed in summer data. Although summertime δ18Oc is considered to be under influence of the fluctuation of δ18Osw caused by local climate such as precipitation, no significant correlation was found between gridded sea surface salinity data and summertime δ18O of seawater (δ18OSW) estimated from δ18Oc and SST. Further examination of coral based SST of Ishigaki Island (SSTIc) revealed that SSTIc can serve as warming trend observed in SST at Ishigaki Port past 40 yeas, and winter SSTIc was significantly affected by East Asian Winter Monsoon from 1958 until 1988/1989 climate regime shift. The δ13Cc was significantly correlated to the seasonal variation of solar radiation. Although δ13Cc seemed to vary with other factors such as biological effects, the δ13Cc can serve as indicators of age and season.
- 資源地質学会の論文
資源地質学会 | 論文
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