Global and local meteoric water lines for δ17O/δ18O and the spatiotemporal distribution of Δ′17O in Earth's precipitation.

Recently, δ¹⁷O and its excess (Δ′¹⁷O) have become increasingly significant "triple-oxygen-isotope" indicators of distinctive hydrological processes in hydrology and climatology. This situation mirrors the research regarding δ¹⁸O and δ²H in the 1960s towards a solid theoretical base and a surge in application examples and field studies worldwide. Currently, systematic global measurements for δ¹⁷O in precipitation are still lacking. As a result, attempts have been made to define a Global δ¹⁷O/δ¹⁸O Meteoric Water Line (GMWL), often by using regional or local datasets of varying systematicity. Different definitions of the global reference slope (λ_ref) for determining Δ′¹⁷O values have been proposed, by ongoing debate around a proposed consensus value of 0.528. This study used worldwide samples archived in the IAEA Global Network of Isotopes in Precipitation (GNIP) to (a) derive a δ¹⁷O/δ¹⁸O GMWL based on four-year monthly records from 66 GNIP stations, (b) formulate local δ¹⁷O/δ¹⁸O meteoric water lines (LMWL) for these stations' areas, and (c) evaluate regional and seasonal variations of Δ′¹⁷O in precipitation. The GMWL for δ¹⁷O/δ¹⁸O was determined to be δ′¹⁷O = 0.5280 ± 0.0002 δ′¹⁸O + 0.0153 ± 0.0013, in keeping with the consensus value. Furthermore, our results suggested that using a line-conditioned ¹⁷O-excess is a viable alternative over the global λ_ref in the context of regional hydrology and paleoclimatology interpretations; however, without challenging the global λ_ref as such. [ABSTRACT FROM AUTHOR]