석산호 골격의 산소 및 탄소 안정동위원소 조성을 이용한 대한해협 지역의 고기후 분석을 위한 선행연구

Abstract

Geochemical compositions of massive coral skeletons have been used as common proxies for seasonal to decadal climate variations in tropical/subtropical regions. Sr/Ca ratio of coral skeletons depends on sea surface temperature (SST) while δ18O does on both SST and δ18O of seawater. Thus, combination of Sr/Ca ratios and δ18O of coral skeletons allows decoupling of sea surface salinity (SSS) and SST from δ18O signal.For palecoclimate reconstruction of Korea Strait region, a 90-cm-long core of living massive reef-building coral, Favia sp. (Family Faviidae), was collected from Iki Island, Japan and the top 28 cm interval was analyzed for δ18O. Favia sp. shows a wide distribution from tropics to middle latitude region and records surrounding environmental conditions in its skeleton. Because commonly used proxy corals such as Porites are absent in middle latitude region, Favia is the only proxy coral that are available in Korea Strait region. δ18O of the top 28 cm interval revealed 41 annual cycles caused by seasonal environmental changes, indicative of its growth period from 1966 to 2007. The measured oxygen and carbon isotope ratios decrease gradually to the present, indicative of SST (and/or precipitation) increase and incorporation of light carbon from fossil fuel burning to the ocean during the last 41 years. The analytical works for Sr/Ca ratios are still in progress. With completion of Sr/Ca measurement, it is possible to reveal SST and SSS variation of the region for the past 41 years. This study will enable the quantitative evaluation of global warming in this region.