[M-IS23] [JJ] Paleoclimatology and paleoceanography

[MIS23-P12] Cellulose oxygen isotopes in Sphagumun from the Bekanbeushi mire, eastern Hokkaido and its application to paleoclimate reconstruction during the last 2000 years

*Hiromichi Sakurai¹, Masanobu Yamamoto¹, Osamu Seki², Takayuki Omori³ (1.Faculty of Environmental Earth Science, Hokkaido University, 2.Low Temperature Research Institute, Hokkaido University , 3.The University Museum, The University of Tokyo, Japan)

Keywords:peat, cellulose, oxygen isotopes

The oxygen isotopic composition of rainfall water has climate signals such as temperature and precipitation. Therefore, we can use the δ¹⁸O values of plant cellulose which preserves the δ¹⁸O values of rainfall water for paleoclimate reconstruction. At the Hani peat mire in northeastern China, paleoclimate reconstruction was attempted using the δ¹⁸O values of cellulose in the peat core, and the variation of the δ¹⁸O values in bulk samples was interpreted that it reflects the variation of temperature (Hong et al., 2009). On the other hands, the analysis of δ¹⁸O in different plant tissues in the same sample from the Rhishiri Minamihama high mire showed that the δ¹⁸O values of sphagnum is lower than the other species (Yamamoto and Seki, unpublished data), suggesting that bulk cellulose δ¹⁸O values may have reflected fractional variation in different tissues. In this study, we separated sphagnum and plant tissues and measured their cellulose δ¹⁸O for peat core samples retrieved from the Bekanbeushi high mire. The δ¹⁸O values of sphagnum were always lower than those of Vaccinium oxycoccos and Calamagrostis neglecta var. aculeolata. Temporal variation in the δ¹⁸O of sphagnum indicated that the value was lower around 1500 years ago and higher around 1100 years ago, corresponding to Dark Age Cold Period and Medieval Warm Period, respectively. The difference of the δ¹⁸O values between plant tisuues and sphagnum has a negative correlation with the δ¹⁸O values of sphagnum. This suggests that relative humidity was higher in warmer periods, which is analogous to modern summer climate in Bekanbeushi area..