Stable isotope ratios (δ2H, δ18O and δ17O) of precipitation in Seoul, Korea, during 2016-2020

Precipitation plays an important role in the global hydrological cycle, and its stable isotope ratio (δ²H, δ¹⁸O and δ¹⁷O) provides useful information for atmospheric circulation in forming precipitation. However, understanding of precipitation stable isotope ratio in mid-latitude is limited by an insufficient and restricted interpretation of hydrological and meteorological processes based on insufficient datasets. To improve domain knowledge, we monitored the water stable isotopes of rainwater and snowfall in Seoul, Korea, during the period of 2016-2022. The δ²H, δ¹⁸O and δ¹⁷O values varied from -120.3 to 3.9 ‰, from -16.58 to 1.21 ‰ and from -8.76 to 0.65 ‰, respectively with characteristic seasonal patterns. The prominent patterns were the isotopic depletion during winter (Dec-Feb; the mean δ²H of -9.39 ‰) under the influence of the Siberian High system and the isotopic enrichment during the spring (Mar-May; the mean δ²H of -2.6 ‰) affected by the Asia monsoon system. The summer season was characterized by the lowest deuterium excess (δ²H­ – 8 x δ¹⁸O; 7.4 ‰). As the interplay of the northeast Asia monsoon, and the Siberian High and the North Pacific High was the major cause of the seasonality of the isotope values, their covariance with temperature or the amount of precipitation was weak. The local meteoric water line had a lower slope and intercept (δ²H = 7.67 x δ¹⁸O + 9.28) compared to the global meteoric water line. Another local meteoric water line between δ¹⁷O and δ¹⁸O appeared to be δ¹⁷O = 0.5312 x δ¹⁸O + 0.0068 with a greater slope and intercept than its global meteoric line.