[M-IS08] Paleoclimatology and paleoceanography

[MIS08-P20] Stalagmite evidence for ¹⁸O-depleted surface water of Japan Sea during the last glacial

*Shota Amekawa¹, Kenji Kashiwagi², Masako Hori³, Tomomi Sone⁴, Hirokazu Kato¹, Tomoyo Okumura⁵, Tsai-Luen Yu⁶, Chuan-Chou Shen^6,7,8, Akihiro Kano¹ (1.Graduate School of Science, The University of Tokyo, 2.Department of Environmental Biology and Chemistry, Faculty of Science, University of Toyama, 3.Division of Natural Sciences, Osaka Kyoiku University, 4.Marine Works Japan LTD., 5.Center for Advanced Marine Core Research, Kochi University, 6.High-precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, 7.Global Change Research Center, National Taiwan University, 8.Research Center for Future Earth, National Taiwan University)

Keywords:stalagmite, East Asian winter monsoon, the last glacial period, Japan Sea

In East Asia monsoonal realm, stalagmites generally record lower δ¹⁸O during warm humid interglacials and higher δ¹⁸O in the cold dry glacials. Here, we present an unusual trend in stalagmite δ¹⁸O between the last glacial interval and Holocene from Fukugaguchi Cave, Niigata Prefecture, where a major moisture source is the East Asian winter monsoon (EAWM) carrying vapor from the warm surface of the Japan Sea. The δ¹⁸O profile of this stalagmite overall exhibits low δ¹⁸O values; the mean sampled glacial δ¹⁸O is distinctly lower than the mid-Holocene mean of another stalagmite (Sone et al., 2013) from the same cave. An interpretation assuming greater vapor transportation than mid-Holocene from the intensified EAWM during the last glacial contradicts marine carbonate records indicating that the entrance of the Tsushima Warm Current into the Japan Sea was interrupted because of lowered sea level. Additionally, our model indicates that the amount effect of winter meteoric water was insignificant. Low δ¹⁸O in the stalagmite dated to glacial intervals in Fukugaguchi Cave most likely resulted from low-salinity and ¹⁸O-depleted surface water, which developed in the isolated Japan Sea. This is the first terrestrial evidence indicating ¹⁸O depletion and salinity of the Japan Sea surface water during the last glacial.