Underlying Climate Controls in Triple Oxygen (16 O, 17 O, 18 O) and Hydrogen (1 H, 2 H) Isotopes Composition of Rainfall (Central Pyrenees)

Studies of rainfall isotopic composition in the Iberian Peninsula are scarce, and to date, none of them have provided analyses of the triple oxygen isotopes, preventing from the complete understanding of current atmospheric processes in this region. We investigate the rainwater delta O-17, delta O-18, and delta D and derived parameters O-17-excess and d-excess in a mountain site in the Central South Pyrenees (Villanua, Huesca, Spain) to identify the main factors (regional and local) controlling the isotopic composition of precipitation at event scale. The samples were collected on a rainfall-event basis during 2 years (from July 2017 to June 2019), and meteorological variables [temperature, relative humidity (RH), and rainfall amount] were monitored at the sampling site. The delta O-17, delta O-18, and delta D values were higher during summer and lower during the rest of the year. In contrast, the O-17-excess and d-excess were lower during summer and higher during the remaining months. We found that the isotopic parameters are weakly correlated with rainfall amount during each event, but they strongly depend on changes in air temperature and moderately on RH. We consider other factors affecting the isotopic composition of rainfall events that resulted to have an important role, such as the influence of the moisture source and trajectory throughout the variations in the synoptic pattern during rainfall events. This dataset can be useful for further comprehensive atmospheric and hydrological studies, with application to paleoclimatic investigations.

Automated summary

Studies on rainfall isotopic composition in the Iberian Peninsula are limited, with few providing analyses on triple oxygen isotopes. This research in the Central South Pyrenees of Spain found that temperature variations play a key role in controlling isotopic composition, along with the influence of moisture sources and airflow trajectories.