동해의 동위원소 기록: 담수 유입의 새로운 증거

Abstract

Two piston cores (M04-PC1A and M04-PC3) sediment taken from the East Sea (Japan Sea) were analyzed, and several previous oxygen isotope records were referred to interpret paleoceanographic evolution that closely related with climatic changes in East Sea. Our new data and detailed comparison with previous record strongly indicated that the oxygen isotope record is not simple but disrupted with locally introduced freshwater input especially since the last glacial maximum (LGM). Strong negative peak which are interpreted distinctive freshwater input during LGM has been continued until almost mid Holocene in most part of Ulleung Basin. This new finding suggested that local effects of oxygen isotope record are influenced by the climatic changes. This timing of freshwater input may synchronized with global warming between the transitional time of MIS 2 and Holocene. In East Sea, regional freshwater influences lasted until 8 ka, and the sluggish ventilation is one of favorable factor for freshwater remain. In contrast with previous works, this study provide that global warming and regional paleoceanography has been played more important role in inverse excursions of oxygen isotope, which resulted in freshwater input to the East Sea just on time of MIS 2 and 6 and the last event has been lasted until 8 ka. Geographic restriction and limited vertical mixing during glacial time are contributed to this specific freshwater input at those times.