Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Poster

M (Multidisciplinary and Interdisciplinary) » M-GI General Geosciences, Information Geosciences & Simulations

[M-GI25] Environmental changes in mountainous area

Tue. May 22, 2018 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Keisuke Suzuki(Department of Environmental Sciences, Faculty of Science, Shinshu University), Yoshihiko Kariya(Department of Environmental Geography, Senshu University), Chiyuki Narama(新潟大学理学部理学科, 共同), Akihiko SASAKI(Department of Geography and Environmental Studies, Kokushikan University)

[MGI25-P17] Spatiotemporal variations in stable isotope ratios of precipitation in the Japanese Alps Region

*Tsukasa Katsuragawa1, Yuki Kurokumo1, Motoshi NISHIMURA1, Shimizu Hironori1, Akihiko SASAKI1, Tsutomu Yamanaka2, Keisuke Suzuki1 (1.Department of Environmental Science, Faculty of Science, Shinshu University, 2.Faculty of Life and Environmental Sciences, University of Tsukuba)

Keywords:precipitation, isotope

We collected precipitation samples and observed weather every month from January 2011 to December 2016 at nine locations in the Japanese Alps Region (Nagano, Matsumoto, Suwa, Omachi, Sugadaira, Norikura, Kamikochi, Shigakogen, Nishihotaka). The collected water samples were brought back to the laboratory to stable isotope analysis to determine δD,δ18O and calculated d-excess. The δ18O in precipitation collected more than once times per month was weighted average using the amount of precipitation and was taken as the average monthly value. As a result of examining the seasonal variation of δ18O from 2011 to 2016, δ18O showed two peaks in spring and summer. In order to investigate the spatial variation, the coefficient of determination between latitude, longitude, altitude and δ18O was calculated, it clearly correlated with altitude from April to October. The cause of the altitude effect was thought to be due to Rayleigh's condensation process. The monthly variation of the δ18O decrease rate also showed a variation close to the monthly average δ18O, suggesting that the seasonal variation of δ18O may also be related to altitude effect. d-excess showed seasonal variation which is high in winter and low in summer. This is thought to be caused by the high d-excess precipitation from the Sea of Japan due to the winter pressure pattern. As a spatial variation, correlation with altitude is high in summer and correlation with longitude is high in winter. The relationship with the altitude in the summer was thought to be related to the Rayleigh's condensation process. The correlation between longitude and d-excess in winter is thought that high d-excess precipitation was brought by the winter pressure pattern to Omachi,Nagano,Sugadaira and Shigakogen in the eastern part of the sampling area.