Collaborative Research: P2C2--Paleoaridity Shifts in a Regional Climatological Hotspot During Abrupt Global Change Events: An Observation-Model Approach

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The general research goal of the research is to evaluate the modern hydroclimate in central Texas that is currently dominated by moisture delivered from the Gulf of Mexico (GoM), tropical Atlantic, and continental recycling, with smaller components from the Pacific. The Great Plains Low-Level Jet generates rainfall while atmospheric conditions govern how much rainwater evaporates, setting the geospatial distribution of aridity. This project will specifically test the hypothesis that this regional distribution of aridity has shifted in terms of both location and intensity as a function of past abrupt global warming and cooling events.The researchers aim to reconstruct speleothem (cave deposits) proxy records from central Texas during episodes of known rapid global change between the last 16,000 years to 11,000 years– spanning the Bølling- Allerød (BA) and Younger Dryas (YD) using existing samples from caves across the Edwards Plateau in central Texas. These caves have been monitored and assessed relative to modern climate parameters, thereby helping to maximize the information from the proxy records. The research team will analyze seven coeval speleothems spanning a 375-kilometer West to East transect, constructing high-resolution oxygen isotope and growth rate proxy records constrained by high-precision Uranium-Thorium chronologies. The resulting speleothem records will be analyzed as a function of longitude to discern changes in moisture source, as well as the steepness and location of the wet-dry gradient. The research approach will: 1) employ proxy system models (PSMs) to assess the influence of cave-specific speleothem growth parameters such as carbon dioxide transport, temperature, water transport and drip rates, and source delta Oxygen-18 isotopes; 2) integrate isotopic variations and growth rates to enhance reconstructions of paleo-aridity; 3) develop proxy time series to ground-truth isotope-enabled general circulation models; and 4) use models to test the regional sensitivities to climate forcing mechanisms, including insolation, greenhouse gases, ice sheet dynamics, and meltwater input to the GoM. Proxy-model comparison will be employed to inform regional circulation dynamics during abrupt change events.This research is important because the climate of the eastern United States is becoming wetter while the western United States is drying. The continental wet-dry line has been shifting eastward over the past four decades and could ultimately degrade water security for millions of citizens in Texas residing in the rapidly growing urban corridor stretching from the Rio Grande Valley to the Dallas-Fort Worth region. This project seeks to understand the mechanisms by which warming and cooling influence aridity in this region to refine and inform projections under a range of future climate scenarios.The potential Broader Impacts include greater understanding of water resources in the western United States, support for a doctoral graduate student, and outreach.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.