Wendt et al. (2025) Controls on the southwest USA hydroclimate over the last six glacial-interglacial cycles

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-11-14
• Authors: Kathleen A. Wendt, Stacy Carolin, Christo Buizert, Simon D. Steidle, R. Lawrence Edwards, Gina E. Moseley, Yuri Dublyansky, Hai Cheng, Chengfei He, Mark J. Warner, Christoph Spötl
• DOI: 10.1038/s41467-025-64963-1

Research Groups

• Institute of Geology, University of Innsbruck, Austria
• College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, USA
• Department of Earth Sciences, University of Toronto, Canada
• Department of Earth Sciences, University of Cambridge, UK
• Department of Earth Sciences, University of Oxford, UK
• Department of Earth Sciences, University of Minnesota, USA
• Institute of Global Environmental Change, Xi’an Jiaotong University, China
• State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, China
• Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami, USA

Short Summary

This study uses an absolute-dated speleothem record from Devils Hole cave 2 and Earth system simulations to identify the primary drivers of hydroclimate and vegetation changes in the southwest USA over the last 580,000 years, finding that temperature-related mechanisms primarily control δ18O variability, with secondary influences from North American ice sheets, while vegetation density is forced by Northern Hemisphere summer intensity.

Objective

• To identify the primary drivers of hydroclimate (δ18O) and environmental (δ13C, vegetation density) changes in the southern Great Basin, southwest USA, over the last six glacial-interglacial cycles (580,000 years) using a precisely dated speleothem record and Earth system model simulations.

Study Configuration

• Spatial Scale: Southern Great Basin, southwest United States (Devils Hole cave 2, southern Nevada; recharge from Spring and Sheep mountain ranges ~80 km southeast, minor inputs ~400 km northeast). Global context for comparisons.
• Temporal Scale: Last six glacial-interglacial cycles, spanning 580,000 years before present (orbital timescales of 10^4 – 10^5 years).

Methodology and Data

• Models used: Water isotope-enabled Community Earth System Model version 1.3 (iCESM1.3) with moisture tagging, OxCal version 4.2 (Bayesian statistical software for age modeling), REDFIT, Lomb-Scargle, Multi-taper method (MTM) for spectral analysis, REDFIT-X for cross-spectral analysis, MATLAB for lagged correlation.
• Data sources:
  • Absolute-dated δ18O and δ13C record from Devils Hole cave 2 (DH2) calcite deposits (speleothem).
  • Uranium (U)-series dating (230Th-234U and 234U-238U).
  • 65°N July insolation data.
  • Original Devils Hole (DH) δ18O record.
  • Palaeo water table reconstructions from DH and DH2 caves.
  • DH2 δ234Ui maxima.
  • Modern rain-bearing trajectories (cluster analyses).
  • Global ice volume inferred from Red Sea relative sea level (RSL).
  • Global atmospheric CO2 record (composite from ice cores: AICC2023, WD2014, DF2021, AICSTAL2024 chronologies).
  • Leviathan δ18O from Nevada stalagmites.
  • LR04 benthic marine δ18O stack.
  • Tropical east Pacific sea surface temperatures (SSTs).
  • Packrat middens (for vegetation shifts).

Main Results

• The extended DH2 δ18O and δ13C record spans 580,000 years with high chronological precision (2σ age uncertainties of 0.3–2%).
• iCESM simulations show a 1.3‰ decrease in annual average δ18O of precipitation at DH2 during the Last Glacial Maximum (LGM) relative to preindustrial (PI), attributed to cooler temperatures and changes in moisture sources.
• LGM simulations indicate a 50% increase in annual precipitation at DH2, primarily during winter, due to a southward displacement of the Pacific Storm Track and enhanced southern North Pacific moisture transport.
• Phasing and midpoint analyses suggest that DH2 δ18O variability on orbital timescales is primarily driven by temperature-related processes (e.g., greenhouse gas concentrations, land-sea temperature gradients, rainout efficiency).
• Secondary drivers of DH2 δ18O variability stem from atmospheric circulation changes linked to North American ice sheets (e.g., Pacific Storm Track modulation).
• DH2 δ18O shows the closest structural and temporal similarity to atmospheric CO2 variability, with DH2 δ18O leading CO2 by an average of ~100 years during glacial terminations (TII-TV).
• Global ice volume lags DH2 δ18O on average, suggesting it is not the primary driver.
• DH2 δ13C, a proxy for vegetation density, is inversely related to DH2 δ18O and shows significant peaks in the precession (23 kyr period) and 100 kyr period bands.
• DH2 δ13C variations are in-phase with Northern Hemisphere summer insolation, indicating increased vegetation density and primary productivity during warm summers.
• A rapid decline in primary productivity occurs during warm interglacial periods when local groundwater recharge declines to less than 50% above modern levels, suggesting a tipping point for environmental decline.

Contributions

• Provides a precisely dated, continuous speleothem record (δ18O and δ13C) from the southern Great Basin spanning six glacial-interglacial cycles (580,000 years), extending previous records.
• Reconciles the Devils Hole climate record with orbital forcing by using a shallow-depth core (DH2) that is not significantly affected by excess 230Th, resolving a long-standing discrepancy.
• Mechanistically disentangles the primary and secondary drivers of orbital-scale hydroclimate (δ18O) variability in the southwest USA using isotope-enabled Earth System Model simulations and comprehensive phasing analyses.
• Identifies the dominant driver of orbital-scale environmental change (δ13C, vegetation density) in the southern Nevada highlands as Northern Hemisphere summer intensity.
• Reveals a critical tipping point for local environmental decline, where vegetation density rapidly decreases when groundwater recharge falls below 50% above modern levels during warm interglacials.
• Sheds new light on the complex relationship between temperature, moisture balance, and vegetation in the southern Great Basin over long timescales, with implications for future climate projections in a water-scarce region.

Funding

• Austrian Science Fund (FWF) project numbers P32751 and P26305
• National Science Foundation (NSF) project numbers 1602940 and 2202913
• National Natural Science Foundation of China project number 41888101
• National Science Foundation (NSF) project number 2102944
• Heising-Simons Foundation grant number 2022-3756

Citation

@article{Wendt2025Controls,
  author = {Wendt, Kathleen A. and Carolin, Stacy and Buizert, Christo and Steidle, Simon D. and Edwards, R. Lawrence and Moseley, Gina E. and Dublyansky, Yuri and Cheng, Hai and He, Chengfei and Warner, Mark J. and Spötl, Christoph},
  title = {Controls on the southwest USA hydroclimate over the last six glacial-interglacial cycles},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-64963-1},
  url = {https://doi.org/10.1038/s41467-025-64963-1}
}

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