Collaborative Research: Quantitative Reconstructions of Last Millennium Hydroclimate and Temperature from the Tropical High Andes

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。地球热带地区的冰川山脉为当地和下游社区提供了重要的淡水资源，并支持丰富多样的生态系统。然而，高海拔地区（1.2万英尺）的变暖预计将在未来加剧，预计到21世纪中叶，许多冰川将消失。维尔卡诺塔山脉（秘鲁）是安第斯山脉第二大冰川山脉，是世界第二大热带冰盖奎尔卡亚的所在地，也是亚马逊河的主要源头。然而，由于仪器记录很少，对20世纪后期之前的温度和降水变化的约束很差。该项目将利用两个位置接近但不同的气候档案：湖泊/泥炭沉积物和冰芯，重建过去几个世纪的温度和水分可用性模式。湖泊和泥炭沉积物随着时间的推移而积累，保存了过去温度和降水的生物和化学指标。项目成果包括从仪器齐全的安第斯湖和泥炭地重建气候，这将提高基于生物标志物的温度代用指标的实用性，并增强叶蜡和冰蝉代用系统模型。该项目还将支持扩大代表性不足群体对STEM的参与，开发K-12教育资源，包括为高中开发气候变化教育模块，提供实践研讨会、培训和体验式学习机会。研究人员将分析Sibinacocha湖（16043英尺）及其周围的沉积物，并使用湖泊和冰模型，使用现有的仪器测量校准，将这些重建结果与Quelccaya冰帽（QIC）冰芯进行比较。结果将为安第斯山脉高海拔地区从寒冷时期（小冰期）过渡到工业时期的空气温度、湖泊温度和湿度变化提供验证和信息。过去1000年的气候模式模拟将把这些变化在多大程度上是由南美夏季风和热带太平洋海面温度变化等远程过程驱动的背景化，将当前安第斯山脉的气候变化置于一个长期的历史背景中。数据将用于重建来自叶蜡的降水δD (δ dprecipitation)，甘油二烷基甘油四醚（GDGTs）的温度，以及来自岩性、整体地球化学和古生态传感器的径流和降水/蒸发。将比较冰川湖泊和非冰川湖泊以及泥炭地的温度重建结果，并使用能量平衡模型对空气/湖泊温度关系进行量化。代理系统模型（PSM）将用于评估冰芯和沉积物的δ18Oprecip、δ dprecp和δDwetland重建对季节和平均年气候变量的敏感性。强迫反应与内部变异性将通过同位素模拟进行研究。由于δ18Oice和δDwax都追踪降水的稳定同位素组成，但对湿度、蒸发和沉积/消融季节的敏感性不同，该项目的双psm方法将允许δ18Oprecip、δ dprecp和温度的多代理重建，同时提供对当地蒸发条件的新约束。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 award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Glaciated mountain ranges in the Earth’s tropical regions provide critical freshwater resources to local and downstream communities and support richly diverse ecosystems. Yet warming at high elevations (12,000’) is expected to amplify in the future, with the disappearance of many glaciers projected by the mid-21st century. The Cordillera Vilcanota (Peru) is the second largest glacierized mountain range in the Andes, is home to world’s second-largest tropical ice cap, Quelccaya and is a principal source of the Amazon River. However, because instrumental records are sparse, variations in temperature and precipitation prior to the late 20th century are poorly constrained. This project will reconstruct patterns of temperature and moisture availability over the past several centuries using two closely-situated but distinct climate archives: lake/peat sediments and ice cores. Lake and peat sediments accumulate over time, preserving biological and chemical indicators of past temperature and precipitation. Project deliverables include climate reconstructions from well-instrumented Andean lakes and peats, which will imporve the utility of biomarker-based temperature proxies, and enhanced leaf wax and ice cory proxy system models. This project will also support efforts to broaden participation from underrepresented groups in STEM and to develop K-12 educational resources, including development of climate change education modules for high schools, and providing hands-on workshops, training and experiential learning opportunities.Researchers will analyze sediments from sites in and around Lake Sibinacocha (16,043’) and use lake and ice models, calibrated using existing instrumental measurements, to compare these reconstructions to Quelccaya Ice Cap (QIC) ice cores. Results will provide validation and information on air temperature, lake temperature, and moisture changes as the high Andes transitioned from a cold period (the Little Ice Age) to the industrial period. Climate model simulations of the past 1,000 years will contextualize the extent to which these changes were driven by remote processes such as the South American Summer Monsoon and sea surface temperature variations in the tropical Pacific, putting current Andean climate change into a long-term historical context. Data will be generated to reconstruct precipitation δD (δDprecip) from leaf waxes, temperature from glycerol dialkyl glycerol tetraethers (GDGTs), and runoff and precipitation/evaporation from lithologic, bulk geochemical, and paleoecological sensors. Temperature reconstructions will be compared from glacial and non-glacial lakes and peatlands, and air/lake temperature relationships will be quantified using an energy balance model. Proxy system models (PSM) will be used to evaluate the sensitivity of δ18Oprecip, δDprecip, and δDwetland reconstructions from ice cores and sediments to seasonal and mean annual climate variables. Forced responses vs. internal variability will be investigated with isotope-enabled Last Millennium simulations. Because δ18Oice and δDwax both track the stable isotopic composition of precipitation but with differing sensitivities to humidity, evaporation, and seasons of deposition/ablation, the project’s dual-PSM approach will allow multiproxy reconstructions of δ18Oprecip, δDprecip, and temperature while providing new constraints on local evaporative conditions.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.