Evaporation exerts fundamental control over the isotopic composition of terrestrial waters, yet the mechanisms involved remain insufficiently constrained. Difficulty in differentiating the roles of diffusion, advection, and atmospheric mixing, combined with variability in the environmental drivers of evaporation - temperature, relative humidity, and wind speed, results in substantial uncertainties, limiting our ability to quantify modern hydrological processes and to robustly interpret geological isotopic archives such as ice cores, speleothems, and lake deposits.

Closed-basin lakes offer a unique opportunity to study evaporation processes since water entering the lake leaves solely by evaporation, making them highly sensitive to isotopic evaporative enrichment. Still, there has not been an attempt to utilize the isotopic composition of closed-basin lakes, with an emphasis on ∆’17O, to understand evaporative enrichment. Here, we study 11 closed-basin lakes across three continents and diverse climatic regimes to assess the mechanistic links between environmental drivers of evaporation and their isotopic signatures. We apply a novel method for high-precision ∆’17O measurements with a Picarro L2140-i isotopic water analyzer achieving high signal-to-noise ratio, adequate for studying evaporation processes. We measured the isotopic composition and chemistry of each lake, its inflow waters and feeding springs, and compiled published hydrological and meteorological properties of each basin. Using this data, we constructed an isotopic hydrological model for the lakes, providing a mechanistic framework to assess the sensitivity and effective influence of different hydrological parameters on evaporative enrichment.

Our results show a remarkable correlation between evaporative enrichment and wind speed, particularly for ∆’17O. The model results enable quantifying the contributions of diffusion, advection, and atmospheric mixing for each lake, and the environmental processes that govern these parameters. This work refines our understanding of evaporative kinetic fractionation in natural settings and provides stronger constraints on the evaporation process, which can be implemented in paleoclimate reconstructions and hydrological models.