figshare
Browse
gieh_a_1132215_sm3574.docx (24.32 kB)

Spatial analysis of annual mean stable isotopes in precipitation across Japan based on an intensive observation period throughout 2013

Download (24.32 kB)
Version 2 2016-09-01, 09:20
Version 1 2016-04-06, 22:11
journal contribution
posted on 2016-09-01, 09:20 authored by Kimpei Ichiyanagi, Masahiro Tanoue

Spatial distribution of annual mean stable isotopes in precipitation (δ18O, δ2H) was observed at 56 sites across Japan throughout 2013. Annual mean δ18O values showed a strong latitude effect, from −12.4 ‰ in the north to −5.1 ‰ in the south. Annual mean d-excess values ranged from 8 to 21 ‰, and values on the Sea of Japan side in Northern and Eastern Japan were relatively higher than those on the Pacific Ocean side. The local meteoric water line (LMWL) and isotope effects were based on the annual mean values from all sites across Japan as divided into distinct regions: the Sea of Japan side to the Pacific Ocean side and Northeastern to Southwestern Japan. Slopes and intercepts of LMWL ranged from 7.4 to 7.8 and 9.8 to 13.0, respectively. Slopes for latitude, altitude, and temperature effects ranged from −0.27 to −0.48 ‰/°N, −0.0034 to −0.0053 ‰/m, and 0.36 to 0.46 ‰/°C, respectively, with statistically significance at the 99 % level. However, there was no precipitation amount effect. From the result of a multiple regression analysis, the empirical formula of annual mean δ18O in precipitation from latitude and altitude for all sites across Japan was determined to be δ18 O = −0.348 (LAT) − 0.00307 (ALT) + 4.29 (R2 = 0.59). Slopes for latitude and altitude ranged from − 0.28 to − 0.51, and − 0.0019 to − 0.0045, respectively. Even though site distribution was uneven, these equations are the first trial estimation for annual mean stable isotopes in precipitation across Japan. Further research performed on the monthly basis is required to elucidate factors controlling the spatiotemporal variability of stable isotopes in precipitation across Japan.

History