Cover Image Credits

The article by Rugenstein and others titled “Clumped isotope constraints on warming and precipitation seasonality in Mongolia following Altai uplift” (p. 28–54) provides new modern water stable isotope data and new clumped isotope-derived temperature estimates for Neogene soil carbonates from western Mongolia. The new modern water data indicate that, today, the Altai decrease the δ¹⁸O of waters in their lee due to the rain shadow that they create. Though the new clumped isotope data indicate a long-term cooling over the course of Neogene, this long-term trend is interrupted by a warming in the late Miocene. Surface uplift of the Altai and establishment of the Altai rain shadow reduced plant cover in western Mongolia, leading to the observed soil warming, despite overall Neogene cooling. Paradoxically, reconstructed soil water δ¹⁸O increases slightly in the lee of the Altai during this period, likely due to a shift in the seasonality of precipitation that accompanied Altai uplift. In combination with regional records of climate, the new isotope data indicate that, though Altai exhumation likely began in the late Paleogene, the Altai only became high enough in the late Miocene to interact with climate, reorganizing precipitation seasonality across a wide swath of northern Central Asia.

Explanation of Cover Figure: This figure shows the spatial distribution of stream and river water isotope data in northern Central Asia. The Altai act to decrease δ¹⁸O in their lee due to orographic precipitation on the windward side of the range (in Russia). The contribution of southerly or more local moisture to the south and east generates higher δ¹⁸O values in stream and river waters.