유공충과 daitom에 대한 안정 산소동위원소:장기간에 걸친 아시아 몬순변화에 대한 의의

Abstract

Long-term climate variability is one of the most important issues for the evaluation in future climate prediction with high resolution scale. Because of the sea surface temperature and its characteristic are associated with the climatic changes, it is important to understand the natural climatic variability. We have speculated the long-term Asian monsoon variation using oxygen isotope values of foraminifer and diatom from the East Sea core sediments and from previous published data in neighboring sites.Several oxygen isotope records from the East Sea core sediment showed that the excursion of the 18O was quite different from those of global. Most data clearly show strong depleted values during the glacial periods when the sea level was lower than present day. These depleted values were interpreted as a consequence of surface water freshening in East Sea and East China Sea in previous works (Oba et al., 1991; Kim et al., 2000; Kubota et al., 2010). Our data also show strong resemblance with previous data that shows coincident variation with East Asian monsoon variability. The timing of surface water freshening is coincident with high precipitation of the East Asia, therefore several depleted oxygen isotope records may associated with East Asia monsoon variability. As a consequence of Asian monsoon variability, surface water freshening events were recorded in sediments around the Korean peninsula. Other proxies such as alkenone sea surface temperature (SST) from the East Sea and East China Sea support that the SST drop and low salinity events since the last interglacial periods have been strongly associated with East Asian monsoon variability, climatic changes.