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

该项目利用一项为期两年的试点研究资金，探索从新墨西哥州西部埃尔马尔派斯国家纪念碑(ELMA)回收的选定数量的熔岩管中可能存储的古气候信息，这是一个具有巨大干旱研究潜力的地区。仪器气候记录表明，北美西南部的干旱模式对太平洋十年代际海洋(PDO)变率以及厄尔尼诺南方涛动(ENSO)和北美季风系统(NAMS)之间的相互作用非常敏感。更深入地了解这些模式的过去(仪器前)行为可能有助于改进对未来干旱和暴雨周期的预测。熔岩管中季节性积累的冰可以提供高分辨率和过时的气候条件变化记录，这将检验最重要的假设，即ENSO和NAMS变异性是过去数千年来西南地区持续存在的特征，以及所有主要气候时期(如中世纪暖期)都是这种年代际到年代际变率模式的一部分。本项目旨在：1)为使用熔岩管中稳定的同位素组成的冰沉积提供概念证据，那里的碳酸盐不能用于三角洲18-氧分析；2)为不断扩大的量化古气候数据集网络作出贡献，这将为理解北美西南部的干旱模式和相关的天气气候遥相关提供重要的空间和时间视角；以及3)发展过去3 000年来西南熔岩管中冰的高分辨率、年代际至年代际尺度的同位素记录。该项目还可能有助于解决其他重要的科学问题，如：1)冰的18度氧和过量的重氢如何表明冰形成过程中水分来源和气温的变化？2)美国西南部的水气候变化如何通过冰的稳定同位素组成反映出来，以及在过去3000年里，气候变化的哪些大规模模式在运行？3)冰沉积是否可以用来识别晚全新世西南地区干旱(特大干旱)的空间分布模式。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测年木炭以及ELMA提供的高分辨率树轮数据一起使用。潜在的更广泛的影响包括对研究生的支持，开发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，这是当前和未来水资源的一个令人担忧的领域。这一奖项反映了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。

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.