Long-term isotope records of precipitation in Slovenia

Long-term meteorological datasets are fundamental for understanding the dynamics of Earth's climate and hydrological systems. Isotopic compositions of precipitation, primarily δ¹⁸O and δ²H, reflect integrated atmospheric processes including moisture source regions, transport pathways, and local climatic conditions such as temperature and precipitation amount. Systematic, long-term observations allow researchers to detect seasonal cycles, inter-annual variability, and long-term trends in atmospheric circulation and hydrometeorological patterns. These datasets are essential for calibrating and validating isotope-enabled climate models and paleoclimate proxies, thereby improving reconstructions of past climate conditions and predictions of future change. Furthermore, they provide a critical reference for assessing the impacts of climate change on regional water resources and identifying shifts in precipitation regimes. As such, long-term precipitation isotope records are indispensable tools in both climate science and water resource management.

This research aims to present evaluation of long-term monthly composite isotope in precipitation records from two Slovenian Isotope in Precipitation (SLONIP, https://slonip.ijs.si/) stations, namely Ljubljana and Portorož, that were compared with neighbouring records from Vienna, Graz and Zagreb.

Stable isotope data from precipitation samples were analysed using the R programming language, involving data cleaning, seasonal and annual aggregation, rolling mean calculation (precipitation-weighted and unweighted), breakpoint detection, and type II regression modelling (reduced major axis and major axis regressions), along with visualization of trends and distributions. Non-parametric statistical tests (Mann-Kendall, Sen’s slope, Kruskal-Wallis) were used to assess temporal and seasonal significance. The applicability of air back-trajectory analysis using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was also explored to help explain the observed trends.

Activities for this presentation were funded in last decade by the ARIS (Grants P1-0143, N1-0054) and IAEA (CRP F33024, F31006, TC RER7013, TC RER7017).