Pilot Project: Exploring the Paleoenvironmental Data Archived in Ice Deposits from Lava Tubes before Its Imminent Loss to Ice Melting

该项目利用资金进行为期两年的试点研究，以探索从新墨西哥州西部El Malpais国家纪念碑（ELMA）精选的熔岩管中恢复的冰芯中可能储存的古气候信息，该地区具有进行干旱研究的巨大潜力。仪器气候记录表明，北美西南部的干旱模式对太平洋年代际海洋（PDO）变率以及厄尔Niño南方涛动（ENSO）与北美季风系统（NAMS）之间的相互作用非常敏感。更深入地了解这些模式过去（仪器前）的行为有助于改进对未来干旱和洪循环的预测。熔岩管中季节性积累的冰可能提供高分辨率和年代准确的气候条件变化记录，这将检验ENSO和NAMS变率是过去几千年来西南地区持续存在的特征，以及所有主要气候时期（如中世纪温暖期）都是这种年代际变率模式的一部分的总体假设。该项目旨在：1)为在无法进行三角洲18氧分析的熔岩管内冰沉积物中使用稳定同位素组成提供概念证明；2)有助于建立一个不断增长的定量古气候数据集网络，为了解北美西南部的干旱模式和相关的天气气候遥相关增加一个关键的时空视角；3)在过去3000年里，从西南地区熔岩管内的冰中提取高分辨率的年代际尺度同位素记录。该项目还可能有助于解决其他重要的科学问题，例如：1)δ 18-氧和氘过量的冰如何指示冰形成过程中水分来源和空气温度的变化？2)美国西南部的水文气候变率是如何通过冰的稳定同位素组成来反映的？在过去3000年里，哪些大尺度气候变率模式在运行？3)冰沉积能否用于识别西南地区晚全新世干旱（特大干旱）的空间格局。为了解决这些问题，冰同位素记录将与从冰中回收的放射性碳定年木炭和ELMA提供的高分辨率树木年轮数据结合使用。潜在的更广泛的影响包括支持一名研究生，开发一个新的古气候数据档案的潜力，以及美国西南部干旱科学的进步，这是一个关注当前和未来水资源的地区。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。

This project uses funding for a two-year pilot study to explore the paleoclimate information potentially stored in ice cores recovered from a select number of lava tubes from El Malpais National Monument (ELMA) in western New Mexico, a region of great potential for drought research.Instrumental climate records indicate that drought patterns in southwestern North America are sensitive to Pacific Decadal Ocean (PDO) variability and to interactions between the El Niño Southern Oscillation (ENSO) and the North American Monsoon System (NAMS). A deeper understanding of the past (pre-instrumental) behavior of these modes could be helpful for improving predictions of future drought and pluvial cycles. Seasonally-accumulated ice in lava tubes may provide an high-resolution and well-dated record of changing climatic conditions that will test the overarching hypothesis that ENSO and NAMS variability were persistent features over the past millennia in the Southwest and that all major climate periods (e.g., Medieval Warm Period) were part of this pattern of decadal-to-interdecadal variability.This project aims to: 1) provide proof of concept for the use of stable isotopic composition of ice deposits in lava tubes where carbonates are not available for delta 18-Oxygen analyses; 2) contribute to a growing network of quantitative paleoclimate datasets that would add a critical spatial and temporal perspective to the understanding of aridity patterns in southwestern North America and associated synoptic climate teleconnections; and 3) develop high-resolution, decadal-to-interdecadal scale isotopic records from ice in lava tubes in the Southwest for the past 3,000 years. The project may also help address other important science questions such as: 1) How delta 18-Oxygen and deuterium excess of ice indicate changes in the moisture source and air temperature during ice formation? 2) How is hydroclimate variability in the south west U.S. reflected by the stable isotopic composition of ice and which of the large-scale modes of climate variability were operating over the past 3000 years? and 3) Can ice deposits be used to identify spatial patterns of aridity (megadroughts) in the Southwest during late Holocene. To address these questions, the ice isotopic record will be used in conjunction with radiocarbon dated charcoal recovered from ice and high-resolution tree-ring data available at ELMA.The potential Broader Impacts include support for a graduate student, the potential for developing a new archive of paleoclimate data, and the advancement of the science of drought in the southwestern U.S., an area of concern for current and future water resources.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.