Collaborative Research: Paleo Records Of GLacier And Climate changes Inferred from Alaskan Lakes (PROGLACIAL)

气候变化对社会构成重大挑战。需要更多的信息将最近的气候变化置于自然气候变率的长期背景下。这些信息有助于预测未来可能的气候趋势，特别是那些涉及气候系统缓慢变化特征的趋势，这些特征将在未来数百年至数千年继续变化。各种地质证据可以用来延长对温度和其他气候变量的观测时间。这个项目的重点是重建美国北极地区阿拉斯加的冰川波动，作为过去数千年气候变化的证据。研究小组将通过研究冰川沉积物来估计过去冰川的大小，这些沉积物由融水流携带并沉积在冰川湖泊中。为该项目收集的沉积物样本也将用于研究地震和火山爆发的迹象，以确定这些破坏性事件在过去发生的频率以及未来可能发生的频率。该项目还将帮助本科生和研究生为STEM劳动力的职业生涯做好准备。冰川覆盖的范围是气候的主要指标。储存在冰川补给（前冰川）湖泊中的沉积物提供了冰川大小波动的独特连续记录。该项目将进一步发展利用冰川石粉丰度的基本沉积指标（体积密度、有机质、粒度、磁化率和积累率）重建前冰期湖泊集水区冰川覆盖范围的能力。通过对阿拉斯加的前冰期湖泊进行采样，研究小组将系统地获得这些众所周知的冰川指标的定量信息，这些指标随冰川大小和其他环境变量而变化。这些信息将用于开发一个数值模型，根据从阿拉斯加中南部和西北部的多个湖泊中提取的沉积物岩心测量的湖泊沉积物特性来估计过去的冰川范围，这些沉积物可以追溯到大约15000年前。除了岩石粉指标外，还将分析沉积物的陆地和水生生产力指标，包括有机色素和生物成因二氧化硅丰度，这些指标适合生成具有十年尺度分辨率的时间序列。这些记录将用于解决与阿拉斯加气候变化的时间和程度有关的基本问题，这些变化发生在上一个主要冰河时期之后。湖泊沉积物的年龄将通过短寿命放射性同位素、火山灰层和放射性碳定年法来确定。该项目还将有助于评估阿拉斯加人口最稠密地区附近与地震和火山活动相关的地质灾害，支持和吸引STEM研究生和本科生以及早期职业研究人员，并开发科学资源，包括受欢迎的阿拉斯加古冰川地图集。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。

Climate change poses a major challenge for society. More information is needed to put recent climate changes into a long-term context of natural climate variability. This information helps to foresee possible future climate trends, especially those that involve slow-moving features of the climate system, which will continue to change over hundreds to thousands of years to come. A variety of geological evidence can be used to extend observations of temperature and other climate variables back in time. This project focuses on reconstructing glacier fluctuations in Alaska, the Arctic region of the United States, as evidence for past climate changes extending back for thousands of years. The research team will estimate past glacier size by studying sediment from glaciers that is carried by meltwater streams and deposited in glacier-fed lakes. The sediment samples collected for this project will also be studied for signs of earthquakes and volcanic eruptions to determine how frequently these damaging events have occurred in the past and will likely occur in the future. The project will also help prepare undergraduate and graduate students for careers in the STEM workforce.The extent of glacier cover is a prime indicator of climate. Sediments stored in glacier-fed (proglacial) lakes provide a uniquely continuous record of glacier-size fluctuations. This project will further develop the ability to reconstruct the extent of glacier cover within the catchment of proglacial lakes using basic sedimentary indicators of glacier rock-flour abundance (bulk density, organic matter, particle size, magnetic susceptibility, and accumulation rate). By sampling proglacial lakes along an environmental gradient of heavily to sparsely glaciated catchments in Alaska, the research team will systematically acquire quantitative information about these well-known glacial indicators, which vary with glacier size and other environmental variables. This information will be used to develop a numerical model to estimate past glacier extent based on lake sediment properties measured in sediment cores taken from multiple lakes in south-central and northwest Alaska that extend back to around 15,000 years. In addition to rock-flour indicators, the sediment will be analyzed for terrestrial and aquatic productivity indicators, including organic pigments and biogenic silica abundance, which are amenable to generating time series with decadal-scale resolution. These records will be used to address fundamental questions related to the timing and extent of climate changes in Alaska that occurred following the last major ice age. The ages of the lake sediment will be determined using short-lived radioisotopes, volcanic ash layers, and radiocarbon dating. This project will also contribute to assessing geological hazards related to seismic and volcanic activity near the most populated area of Alaska, supporting and engaging STEM graduate and undergraduate students and early career researchers, and developing scientific resources, including the popular Alaska PaleoGlacier Atlas.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.