Abstract
Earth’s climate history is traced through the long-term covariance between the isotopic (δ18O) composition of archived meteoric waters (groundwater, ice cores) with air temperature (T) and amount of precipitation (P). To assess recent multi-decadal climatic changes, we analysed δ18O, T and P, and the relationships between these parameters at 20 stations having 60 years of continuous monthly isotopic records. Using nonparametric regressions and time series modelling we found significant linear and non-linear relationships for δ18O with T and P and showed that the δ18O dependency on these two parameters varied over decadal scales, thereby revealing complex relationships related to recycled moisture, large-scale convective processes and atmospheric-oceanic oscillations. Due to multiple factors controlling the δ18O composition of precipitation including P and T effects, we found that time-varying relationships between δ18O in precipitation P and T were better explained using the non-linear regressions. Our results affirmed that δ18O distributions in global precipitation are integrative indicators of climate dynamics whose patterns can be applied to better understand region-specific climatic changes in the present, past, and future.
Highlights
Analysis of long-term (60-year) global precipitation δ18O data and the relationships with P and T revealed diverse spatial climatic response patterns that cannot be simplistically unified in space and time
Stations with indistinguishable T and P effects and low δ18O variability revealed that other interdependent process are affecting T and the δ18O composition of meteoric water, rather than mainly local climatic conditions
Long-term records of stable isotopes and meteorological data for monthly composites of precipitation spanning ca. 60 years were obtained from the International Atomic Energy Agency (IAEA) the Global Network for Isotopes in Precipitation (GNIP)[42]
Summary
Analysis of long-term (60-year) global precipitation δ18O data and the relationships with P and T revealed diverse spatial climatic response patterns that cannot be simplistically unified in space and time. Over the multi-decadal sampling period we observed that the δ18O dependency on T and P was not constant over time, which indicates multiple effects of climate dynamics including global and regional scale hydrologic processes and oceanic cycles.
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