Improved high-resolution global and regionalized isoscapes of δ18O, δ2H and d-excess in precipitation

Patterns of delta O-18 and delta H-2 in Earth's precipitation provide essential scientific data for use in hydrological, climatological, ecological and forensic research. Insufficient global spatial data coverage promulgated the use of gridded datasets employing geostatistical techniques (isoscapes) for spatiotemporally coherent isotope predictions. Cluster-based isoscape regionalization combines the advantages of local or regional prediction calibrations into a global framework. Here we present a revision of a Regionalized Cluster-Based Water Isotope Prediction model (RCWIP2) incorporating new isotope data having extensive spatial coverage and a wider array of predictor variables combined with high-resolution gridded climatic data. We introduced coupling of delta O-18 and delta H-2 (e.g., d-excess constrained) in the model predictions to prevent runaway isoscapes when each isotope is modelled separately and cross-checked observed versus modelled d-excess values. We improved model error quantification by adopting full uncertainty propagation in all calculations. RCWIP2 improved the RMSE over previous isoscape models by ca. 0.3 parts per thousand for delta O-18 and 2.5 parts per thousand for delta H-2 with an uncertainty delta O-18 and < 8 parts per thousand for delta H-2 for most regions of the world. The determination of the relative importance of each predictor variable in each ecoclimatic zone is a new approach to identify previously unrecognized climatic drivers on mean annual precipitation delta O-18 and delta H-2. The improved RCWIP2 isoscape grids and maps (season, monthly, annual, regional) are available for download at .

Automated summary

Patterns of delta O-18 and delta H-2 in Earth's precipitation are vital for various scientific researches. The Regionalized Cluster-Based Water Isotope Prediction model (RCWIP2) has improved prediction accuracy by incorporating new data and coupling delta O-18 and delta H-2. The improved isoscape grids and maps are available for free download.