GREAT BASIN CLIMATE OVER THE LAST SEVEN GLACIAL-INTERGLACIAL CYCLES: THE NEW DEVILS HOLE CAVE RECORD (Invited Presentation)

The North American southwest underwent large swings in climate throughout the Quaternary, as illustrated by the repeated expansion and desiccation of large lakes on orbital timescales. Due to difficulties in dating and archive preservation prior to the last glaciation, however, the evolution of the climate over multiple-glacial-interglacial cycles remains poorly understood. Here we present a 736,000-year oxygen (δ¹⁸O) isotope timeseries from Devils Hole Cave 2 (DH2) in southern Nevada. The DH2 record reveals climate variability in southwest North America over the last seven glacial-interglacial cycles with average resolution of 200 years. Its chronology is anchored by 114 uranium-series ages with the relative dating precision of 0.3-2% (2𝞂). During all recorded Terminations (I-VI, VIII), the shift towards interglacial δ¹⁸O values broadly coincides with the rise in boreal summer insolation, as previously observed by Moseley et al. (2016) during Termination II. The DH2 δ¹⁸O spectral structure shows significant peaks in both the precession (23 kyr and 19 kyr periods) and obliquity (41 kyr periods) orbital bands, and around the 100 kyr period. Our findings support the conclusion by Moseley et al. (2016) that the DH2 δ¹⁸O timeseries is in firm agreement with the Milankovitch theory of orbital forcing. The DH2 δ¹⁸O timeseries shows remarkable similarities to atmospheric CO₂ variability, as shown by regression analysis and indistinguishable phasing within dating uncertainties. The mid-points of Terminations II-V in the DH2 timeseries [132.15 ka (II), 244.03 ka (III), 341.12 ka (IV), and 430.79 ka (V)] are within dating uncertainties of CO₂ mid-points and coincide with the associated weak Asian monsoon interval for each Termination. DH2 δ¹⁸O variability is largely attributed to regional temperatures, which are influenced by greenhouse gases on orbital timescales. This supports recent isotope-enabled atmospheric circulation simulations which suggest that depletion of precipitation δ¹⁸O in the Great Basin is controlled by land-sea thermal contrast (Tabor et al., 2021). Further analysis of site-specific simulations in this study provides additional insight into the drivers of glacial-interglacial precipitation δ¹⁸O variability at DH2.

Moseley, G. et al. (2016). Science, 351, 165-168.

Tabor, C. et al., (2021). QRS, 274, 107255.