[A-HW19] Hydrology & Water Environment

[AHW19-P10] Stable Isotopes in Precipitation for 2017-2021 at Fairbanks, Alaska

Kento TAKAKURA¹, *Kimpei Ichiyanagi¹, Hotaek Park², Masahiro TANOUE³ (1.Kumamoto University, 2.JAMSTEC, 3.Meteorological Research Institute)

Keywords:stable isotope ratio, precipitation, Alaska, temperature effect

The stable isotope ratios of precipitation are positively correlated with temperature, called the temperature effect. Stable isotopes of precipitation are therefore useful tracers for reconstructing past climates and estimating air masses and water sources. The purpose of this study is to investigate the factors that control the seasonal variation of stable isotopes in precipitation observed in inland Alaska. Precipitation sampling was conducted at the University of Alaska Fairbanks from October 2017 to August 2021, resulting in a total of 275 precipitation samples. Monthly mean stable isotope values were calculated weighted by daily precipitation. As a result, stable isotopes of precipitation showed distinct seasonal variation, with δ18O from -31.5‰ in winter to -11.9‰ in summer, and d-excess from -10‰ in summer to +12‰ in winter. A positive correlation was found between monthly mean δ18O and surface air temperature, with a correlation coefficient of 0.76, which was statistically significant. The slope of the regression equation was 0.27‰/℃, indicating a temperature effect. A positive correlation between them was obtained for spring, autumn, and winter, but no significant correlation was observed only in summer. Furthermore, backward trajectory analysis indicated that the origin of water vapor came from the Arctic and Pacific Oceans, respectively, during relatively high and low δ18O precipitation in winter. For further study, we would like to consider the factors control the stable isotopes in precipitation from the atmospheric circulation field and water vapor origins using the isotope circulation model.