Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-HW Hydrology & Water Environment

[A-HW24] Isotope Hydrology 2019

Mon. May 27, 2019 9:00 AM - 10:30 AM 105 (1F)

convener:Masaya Yasuhara(Rissho Univ.), Kohei Kazahaya(Geological Survey of Japan, AIST), Shinji Ohsawa(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Kazuyoshi Asai(Geo Science Laboratory), Chairperson:Masaya Yasuhara(Rissho Univ.), Noritoshi Morikawa(産業技術総合研究所活断層・火山研究部門)

9:45 AM - 10:00 AM

[AHW24-03] Quantitative reconstruction of the humidity in the moisture source region based on the 17O-excess in precipitation on a subtropical island

Yuina Uechi1, *Ryu Uemura1 (1.University of the Ryukyus)

Keywords:17O, stable isotope, monsoon, precipitation

A high-precision analysis of the triple oxygen isotope composition of water provides a new tracer denoted as 17O-excess. In theory, the 17O-excess can be interpreted as variations in the relative humidity in moisture source regions for precipitation. However, recent studies on 17O-excess in the precipitation in polar and dry regions suggest the importance of snow formation and raindrop re-evaporation processes. To date, whether humidity in the moisture source region can be quantified based on observations of 17O-excess in precipitation has not been proven. Here, we show a 2 year record of the 17O-excess in precipitation on a maritime island in the East Asian monsoon region, Okinawa, Japan. We demonstrate that the reconstructed relative humidity is quantitatively consistent with observations in the oceanic moisture source region. This result suggests that the 17O-excess in precipitation on the subtropical island is determined largely by diffusional fractionation during evaporation in the ocean. These results suggest that the 17O-excess in precipitation in tropical and subtropical regions is a unique quantitative tracer for the relative humidity in oceanic moisture source regions and thus will be a useful tracer and proxy for hydrological and paleoclimate studies.

Reference:
Uechi, Y. and R. Uemura, Dominant influence of the humidity in the moisture source region on the 17O-excess in precipitation on a subtropical island, Earth and Planetary Science Letters, in press.