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

这项研究的总体研究目标是评估得克萨斯州中部的现代水气候，目前该地区以墨西哥湾(GOM)、热带大西洋和大陆循环输送的水分为主，来自太平洋的成分较小。大平原低空急流产生降雨，而大气条件控制着雨水的蒸发量，决定了干旱的地理空间分布。这个项目将专门测试这一假设，即随着过去突然的全球变暖和变冷事件，这种地区干旱的分布在位置和强度方面都发生了变化。研究人员的目标是利用德克萨斯州中部爱德华兹高原洞穴的现有样本，重建过去16,000年到11,000年间已知快速全球变化时期德克萨斯州中部洞穴沉积(洞穴沉积)的替代记录。根据现代气候参数对这些洞穴进行了监测和评估，从而有助于最大限度地利用代理记录中的信息。研究小组将分析横跨西向东375公里的七个同时代洞穴，构建受高精度铀-钍年代学约束的高分辨率氧同位素和生长速度替代记录。由此产生的洞穴记录将作为经度的函数进行分析，以辨别水汽来源的变化，以及干湿梯度的陡度和位置。研究方法将：1)使用替代系统模型(PSM)来评估洞穴特有的洞穴洞穴生长参数的影响，如二氧化碳输送、温度、水输送和滴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加强古干旱的重建；3)开发替代时间序列以建立地面真实同位素启用的大气环流模型；以及4)利用模型来测试区域对气候强迫机制的敏感性，包括太阳辐射、温室气体、冰盖动力学和向全球海洋观测机制的融水输入。这项研究很重要，因为美国东部的气候正在变得更加潮湿，而美国西部正在变得干燥。过去40年，大陆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，这些人居住在从格兰德河谷到达拉斯-沃斯堡地区的快速增长的城市走廊上。该项目旨在了解气候变暖和变冷对该地区干旱的影响机制，以完善和提供在一系列未来气候情景下的预测。潜在的更广泛的影响包括更好地了解美国西部的水资源，对博士生的支持，以及更广泛的外游。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.