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，该气候目前主要由墨西哥湾（GoM），热带大西洋和大陆循环输送的水分主导，太平洋的成分较小。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，确定了干旱的地理空间分布。 该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，这是过去全球突然变暖和变冷事件的函数。（洞穴沉积物）在过去16,000年至11000年间已知的快速全球变化期间，德克萨斯州中部的代理记录，000年-跨越博林-阿勒罗德（BA）和新仙女木（YD），使用德克萨斯州中部爱德华兹高原洞穴的现有样本。对这些洞穴进行了监测，并根据现代气候参数进行了评估，从而有助于最大限度地利用代用记录中的信息。 该研究小组将分析横跨375公里的西向东样带的七个同时代洞穴沉积物，构建高分辨率氧同位素和生长速率代理记录，这些记录受到高精度铀钍年表的约束。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，以及干湿梯度的陡度和位置。研究方法将：1）采用代理系统模型（PSM）评估洞穴沉积物生长参数的影响，如二氧化碳输送、温度、水输送和滴水速率，以及源三角洲氧-18同位素; 2）整合同位素变化和生长速率，以增强古干旱的重建; 3）开发代理时间序列，以支持地面真实同位素的大气环流模型;以及4）使用模型来测试区域对气候强迫机制的敏感性，包括日照、温室气体、冰盖动态和向墨西哥湾输入的融水。代理模式的比较将被用来告知区域环流动力学在突变事件。这项研究是重要的，因为美国东部的气候变得更加潮湿，而美国西部是干燥的。在过去的四十年里，大陆的干湿线一直在向东转移，最终可能会降低德克萨斯州数百万居民的水安全，他们居住在从格兰德河山谷延伸到达拉斯-沃斯堡地区的快速增长的城市走廊上。该项目旨在了解变暖和变冷影响该地区干旱的机制，以改进和通报一系列未来气候情景下的预测。潜在的更广泛影响包括更好地了解美国西部的水资源，支持博士研究生，该奖项反映了NSF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.