Geomorphic Response of Glacial Decoupling in Alpine Regions in Response to Climate Warming: Icy Debris Fans and Early Paraglacial Landscape Evolution

近几十年来，气候变暖的影响在高山冰川地区尤为显著。许多山谷冰川已经与高层冰盖脱钩，暴露出主要的悬崖，目前正在经历以冰为主导的过程，包括冰崩、崩塌、结冰的泥石流和泥石流。该项目将对这些悬崖底部正在演变的一套动态冰层主导的地貌(这里称为冰屑扇)进行首次详细研究。以前对冰川消融地貌的研究，形成于副冰期，描述了冲积扇和距骨锥的快速发展，然而，以冰为主的大规模消融过程对地形演变的影响大多没有被认识到。研究将在阿拉斯加和新西兰的研究地点进行，这些地点提供了为与冰屑扇有关的地貌开发准确的演化模型所需的最大种类的形态形成环境和时间阶段。这项研究将集中于野外调查，旨在破译形成冰屑扇的沉积过程，集水形态测量对扇形态的影响，并将冰扇的沉积学特征与类似的不以冰为主的地貌相比较。通过使用陆基激光雷达测绘、延时摄影和遥控飞机的新组合，我们将量化不同环境中形成的扇的沉积过程和形态随时间的速率和体积的变化。地表沉积学数据和地下地球物理调查将记录冰屑扇的沉积结构。一旦整合，这些数据集将对冰屑扇的形成和演化产生重要的制约，并对评估随时间的地貌演变产生影响，包括区分冰屑扇的沉积物与相关但更深入研究的地貌，如冲积扇和距骨锥。最近的气候变暖对冰川产生了重大影响，将冰从高海拔的冰盖输送到低海拔的山谷冰川。气候变暖导致许多山谷冰川与其来源冰盖脱钩，从而暴露出主要的基岩悬崖。这些悬崖非常不稳定，以冰为主的极端侵蚀过程为特征。如冰崩、冰雪泥石流、冰雪雪崩和崩塌。冰川消融后，迅速形成的地貌被称为冰屑扇，主导着这片新形成的地貌，在夏季的几周里，数百次灾难性的冰崩和冰川泥石流很常见。这项研究直接解决了与现代全球变暖有关的几个关键科学问题，并将通过开发一种涉及延时摄影、地面雷达成像和遥控飞机的新方法，推动崎岖高山环境中地形分析的研究方法。鉴于冰屑扇是新发现的地貌，我们的研究有望为冰川消融高山环境中地貌演化的本质提供新的视角。预期结果将对改善高山冰川消融环境中的地质灾害评估和流域管理产生直接影响。具体地说，研究结果将使我们更好地了解下游沉积物和水通量的变化，提高我们对阿拉斯加和新西兰国家公园偏远地区的危险和安全的了解。随着高山环境中冰川继续融化和变薄，预计各种冰川危害将会增加，包括落石、冰坝溃决洪水和冰雪崩塌。随着斜坡变得越来越不稳定，冰块扇子将变得更加普遍。更好地描述这些鲜为人知的过程和地貌的性质和频率，将有助于减轻这些正在影响越来越大的地理区域的危险现象的影响。该项目得到了地貌学和土地利用动态计划、NSF国际科学和工程办公室以及EAR的教育和人力资源计划的支持。

In recent decades, the impacts of climate warming have been especially significant in alpine glaciated regions. Many valley glaciers have decoupled from high-level icecaps to expose major escarpments now experiencing rapid mass wasting by processes dominated by ice, including ice avalanching, rockfalls, icy debris flows, and slush avalanches. This project will conduct the first detailed study of a suite of dynamic ice-dominated landforms (here termed icy debris fans) that are evolving at the base of these escarpments. Previous studies of deglaciating landscapes, formed during periods known as paraglacial, have described rapid development of alluvial fans and talus cones, however, the influence of ice-dominated mass wasting processes on landform evolution has mostly gone unrecognized. Research will occur at study sites in Alaska and New Zealand that provide maximum variety of morphogenetic settings and temporal stages needed to develop an accurate evolutionary model for landforms associated with icy debris fans. This research will focus on field investigations aimed at deciphering the depositional processes that form icy debris fans, the influence of catchment morphometry on fan morphology, and distinguishing sedimentological characteristics of icy fans compared with similar landforms not dominated by ice. By using a novel combination of ground-based LiDAR mapping surveys, time-lapse photography, and remote-control aircraft, we will quantify variations in the rates and volumes of depositional processes and morphology of fans formed in different settings through time. Surficial sedimentological data and subsurface geophysical surveys will document the sedimentary architecture of icy debris fans. Once integrated, these datasets will yield important constraints on the formation and evolution of icy debris fans and hold implications for evaluating landscape evolution through time, including distinguishing the deposits of icy debris fans from related but more thoroughly studied landforms such as alluvial fans and talus cones. Recent climate warming has had major impacts on glaciers delivering ice from high-level icecaps to lower elevation valley glaciers. Warming has resulted in decoupling of many valley glaciers from their source icecaps, thereby exposing major bedrock escarpments. These escarpments are highly unstable and characterized by extreme erosional processes dominated by ice ? such as ice avalanches, icy debris flows, slush avalanches, and rockfall. Rapidly-forming landforms known as icy debris fans dominate this newly-forming landscape immediately following deglaciation where hundreds of catastrophic ice avalanches and icy debris flows are common during summer weeks. This research directly addresses several key scientific problems linked to modern global warming and will advance research methods of landform analysis in rugged alpine environments by developing a novel methodology involving time-lapse photography, ground-based radar imaging, and remote-controlled aircraft. Given that icy debris fans are newly discovered landforms, our research holds promise for providing new perspectives on the nature of landform evolution in deglaciating alpine environments. The anticipated outcomes will have direct implications towards improving assessment of geohazards and watershed management in deglaciating alpine settings. Specifically, results will provide a better understanding of changes in sediment and water flux downstream, improving our understanding of hazards and safety in back country areas of national parks in Alaska and New Zealand. As glaciers continue to melt and thin in alpine environments, a wide range of glacial hazards are expected to increase, including rockfalls, breakout floods from ice dams, and ice avalanches. Icy debris fans will become more prevalent as slopes become increasingly unstable. Better characterization of the nature and frequency of these poorly understood processes and landforms will help mitigate the impacts of these hazardous phenomena that are affecting increasingly larger geographic regions.This project is supported by the Geomorphology and Land Use Dynamics Program, NSF's Office of International Science and Engineering, and EAR's Education and Human Resources program.