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

该研究的总体研究目标是评估德克萨斯州中部的现代水文气候，该气候目前由墨西哥湾（GoM）、热带大西洋和大陆循环输送的水分主导，太平洋的水分较少。大平原低空急流产生降雨，而大气条件决定了多少雨水蒸发，从而决定了干旱的地理空间分布。这个项目将专门测试这样一个假设，即干旱的区域分布在位置和强度方面都发生了变化，这是过去突然的全球变暖和变冷事件的函数。研究人员的目标是利用从德克萨斯州中部爱德华兹高原的洞穴中获得的现有样本，重建德克萨斯州中部在过去16000年至11000年间已知的全球快速变化时期的洞穴（洞穴沉积物）代用记录，这些变化跨越了b.o lling- allerlod （BA）和Younger Dryas （YD）。对这些洞穴进行了与现代气候参数相关的监测和评估，从而有助于最大限度地利用代用记录提供的信息。研究小组将分析横跨375公里西向东样带的7个同时期洞穴，在高精度铀钍年表的约束下构建高分辨率氧同位素和生长速率代理记录。由此产生的洞穴记录将作为经度的函数进行分析，以辨别水分来源的变化，以及干湿梯度的陡峭度和位置。研究方法将：1)采用代理系统模型（psm）评估洞穴生长参数（如二氧化碳输运、温度、水输运和滴水速率）和源δ氧-18同位素的影响；2)整合同位素变化和生长速率，加强古干旱区重建；3)建立代表时间序列的地层真实同位素总循环模型；4)利用模式测试区域对气候强迫机制的敏感性，包括日照、温室气体、冰盖动力学和墨西哥湾融水输入。代理模式的比较将用于突变事件期间的区域环流动力学。这项研究很重要，因为美国东部的气候越来越湿润，而美国西部的气候却越来越干燥。在过去的四十年里，大陆的干湿线一直在向东移动，最终可能会降低德克萨斯州数百万居民的水安全，这些居民居住在从大格兰德山谷到达拉斯-沃斯堡地区快速发展的城市走廊。该项目旨在了解该地区变暖和变冷影响干旱的机制，以便在一系列未来气候情景下改进和预测。潜在的更广泛的影响包括加深对美国西部水资源的了解，支持博士研究生和推广。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.