Controls on the southwest USA hydroclimate over the last six glacial-interglacial cycles

The Great Basin in the southwest United States experienced major hydroclimate shifts throughout the Quaternary. Understanding the drivers behind these past changes has become increasingly important for improving future climate projections. Here, we present an absolute-dated δ¹⁸O and δ¹³C record from Devils Hole cave 2 (southern Nevada) that reveals climate and environmental changes in the southern Great Basin over the last 580,000 years. Water isotope-enabled Earth system simulations and phasing analysis show that temperature-related mechanisms are a primary driver of δ¹⁸O variability, with additional drivers stemming from processes linked to North American ice sheets. Vegetation density in the highlands of southern Nevada is primarily forced by Northern Hemisphere summer intensity. A rapid decline in primary productivity occurs during warm interglacial periods when local groundwater recharge declines to <50% above modern. Our study sheds new light on the relationship between temperature, moisture balance, and vegetation over the last six glacial-interglacial cycles.