Since temperature and precipitation amounts are anticor- related on an interannual timescale (Fig. 5), we interpret low ?D values to indicate both relatively cool and wet conditions. In addition to fluctuations in mean annual precipitation iso- topes, snowmelt and delivery to plants may vary. We suggest that a high proportional contribution of water derived from snowmelt, after relatively long and wet winters with high amounts of snowfall, can further lead to more negative ?D leaf wax values.

Higher isotopic values in the summer compared to the winter (Yao et al., 2013; Bowen and Revenaugh, 2003) suggest that monthly values are indeed driven by temperature. If these seasonal controls also determine interannual variations in the isotopic composition of precipitation then temperature is likely to be a major factor explaining the reconstructed hydrogen isotopic variability. A higher percentage of growing season rainfall (relative to total water used by plants) would result in higher deltaD values.

Higher isotopic values in the summer compared to the winter (Yao et al., 2013; Bowen and Revenaugh, 2003) suggest that monthly values are indeed driven by temperature. If these seasonal controls also determine interannual variations in the isotopic composition of precipitation then temperature is likely to be a major factor explaining the reconstructed hydrogen isotopic variability. A higher percentage of winter snowmelt (relative to total water used by plants) would result in lower deltaD values.

This amount effect lowers the summer precipitation isotopic com- position, dampens the seasonality of the mean precipitation of isotopic values and lowers the integrated annual precip- itation isotopic composition. Hence, in drier years average ?D values will be D-enriched relative to wetter years, and likewise warmer years will be D-enriched relative to colder years (Fig. 4b). Given the low precipitation amounts in this arid region today, the amount effect is likely to remain sec-ondary to the temperature controls on isotopic composition apparent in the seasonal cycle.