| 14 Apr 2026
A spatially resolved 39-month dataset of precipitation water isotopes over Jeju volcanic island, Korea
Abstract. Spatially and temporally resolved observations of precipitation water isotopes are essential for quantifying groundwater recharge, constraining hydroclimate variability, and calibrating paleoclimate proxies, yet such datasets remain scarce for monsoon-influenced volcanic islands characterized by steep topography and strong maritime and continental interactions. Here, we present a spatially resolved 39-month dataset (September 2000 to December 2003) of precipitation water isotopes (δ¹⁸O, δD, and d-excess) collected from 15 monitoring stations across Jeju volcanic island, South Korea, spanning elevations from 10 to 1,500 m above sea level. The dataset comprises 462 precipitation samples and captures pronounced seasonal variability together with island-wide spatial gradients. Monthly mean isotope values exhibit a distinct monsoon-driven seasonal cycle, with isotopic depletion during summer and enrichment during winter, which is well represented by sinusoidal fitting for δ¹⁸O and δD. Spatial analyses reveal a clear altitude effect, with mean lapse rates of −0.15 ‰ per 100 m for δ¹⁸O and −1.1 ‰ per 100 m for δD, while d-excess displays weaker elevation dependence but pronounced seasonal sensitivity to moisture source humidity and evaporation conditions. This dataset provides a robust observational basis for developing high-resolution regional isoscapes, estimating groundwater recharge elevations, and serving as benchmark input and validation data for isotope-enabled climate and hydrological models. All data are openly available with comprehensive metadata, enabling direct reuse in hydrological, climatological, and paleoclimate studies across monsoon-affected volcanic island environments.
Lee et al. present and discuss a new database of d18O and d2H in precipitation in Jeju Island (Korea). Apart from the usefulness of such data for scientific and practical purposes (e.g., water resources management) it is worth praising the authors for “digging up” decades all data, rather that just leave sit in drawers – it could set an example for groups, as well. To this extent, I suggest adding 1-2 lines, both in the abstract and the main text on the usefulness of such approach. Also, to better support this, I would suggest the authors to add a brief (within the limitations imposed by the journal’s instructions) discussion of how their data fits/complements similar studies in the region (see https://doi.org/10.1016/j.ejrh.2026.103141 and references therein).
Overall, given the scope of the journal, I would reduce the length of the discussions section, perhaps remove also the entire sections 4.3 and 4.4 and leave these for a dedicated paper. Some of the discussion could be reduced in length, as they are mostly theoretical considerations.
A couple of observations detailed below might nevertheless help the authors and future readers better shape and understand, respectively, the paper.
Specific comments