Rainshadow effect on hydrogen isotopes in leaf wax n-Alkanes across the Cascade Mountains of Washington, USA

Hydrogen isotope ratios are sensitive tracers of the water cycle with potential to constrain timing mountain building episodes in geologic past. This study presents hydrogen (2H/1H or δ2H) n-alkanes derived from leaf wax terrestrial plants, collected trees and soils along an east–west transect across Cascade range Washington State, USA. Along this transect, δ2H values (δ2Halkane) surface gymnosperm leaves well-correlated mean annual precipitation (δ2Hprecip) instrument-model reanalysis products (R2 = 0.346 0.558, p < 0.001 for soil alkanes, R2 0.667 0.844, alkanes) measured nearby waters 0.451, 0.001). All data show increasing deuterium (2H) depletion distance coast response Rayleigh distillation induced by Mountains. Assessed within context a global dataset 235 published δ2Halkane vs δ2Hprecip, Cascades results statistically indistinguishable. However, δ2Hprecip differ set 87 such sites, steeper relationship. is attributed regional differences between other locations that include higher latitude, altitude, presence strong, narrow climatic gradient. The strong imprint rainshadow on validates its use as proxy uplift when suitable sedimentary rocks.