Terminus Dynamics and Active Deformation of Proglacial Sediments at an Advancing Glacier: Taku Glacier, Alaska

前进冰川的终点动力学和前冰川沉积物的主动变形：阿拉斯加塔库冰川

• 批准号: 0221307
• 负责人: Roman Motyka
• 金额: $ 35.65万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-15 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0221307&HistoricalAwards=false
• 关键词: Terminus; Dynamics; Active; Deformation; Proglacial

Motyka00221307Taku Glacier has been steadily advancing for the last several decades, excavating its bed and entrenching itself into glaciomarine, fluvial, tidal, sediments and glacier outwash deposits. The cause of this advance is related to the advance phase of the "tidewater glacier cycle". A 19th century calving retreat resulted in a high area accumulation ratio (AAR) during most of the 20th century (~ 0.90). The high AAR and gradual diminishment of calving due to infilling of the fjord by glacial and fluvial sediments resulted in a positive net balance for several decades, driving the current advance 7 kilometers (km) since 1890. Taku Glacier therefore presents an ideal setting and rare opportunity for the study of slow glacier advance onto and into soft sediments. Continued thickening of ice in the terminus region indicates this advance should continue over the next several years. Reconnaissance observations have documented contemporaneous deformation of proglacial sediments about 200 meters (m) in front of the terminus and prominent bulges up to 10 m high have formed in the compressed sediments with buckling of the overlying soil and vegetation. The Principal Investigators will study the dynamics of the advancing glacier terminus and investigate the effects of this advance on the proglacial geomorphology. Surface velocities, strain rates, and surface elevation changes will be measured both on the glacier terminus and on proglacial features, along with measurements of changes in terminus position. Ground penetrating radar (GPR) and radio echo sounding (RES) will be used to define the glacier geometry and the nature of the bed. They will repeat RES surveys to investigate ongoing subglacial sediment excavation and entrenchment. GPR will also be used to develop a 3-dimensional picture of the structure of the proglacial sediments and their deformation. Existing and new markers on the sediments will measure motion and strain. A key feature of this study will be simultaneous measurement of short-term changes in terminus ice speed and proglacial sediments using precision GPS over several months. Terminus dynamics and the mass balance are integral parts of glacier response theories, but they are poorly understood. The Principal Investigators will use finite element analyses to investigate the deformation and stress fields in the terminal ice wedge and of the sub- and proglacial sediments, using strain data and geometry as constraints. Their aim is to understand the detailed dynamics of terminus advance and the rheological properties of the sediments and the ice near the terminus. They will also investigate the relation between glacier thickening and terminus advance, using our continuing airborne altimetry and photogrammetric measurements of surface elevation.

莫蒂卡00221307塔库冰川在过去几十年中一直在稳步前进，挖掘其河床，并将自己嵌入冰海、河流、潮汐、沉积物和冰川沉积物中。 这种提前的原因与“冰川旋回”的提前阶段有关。19世纪的产犊消退导致了20世纪大部分时间内的高面积累积比（AAR）（~ 0.90）。由于峡湾被冰川和河流沉积物填充，高AAR和产犊的逐渐减少导致了几十年的正净平衡，自1890年以来推动了目前的前进7公里。因此，塔库冰川为研究冰川缓慢前进到软沉积物上提供了一个理想的环境和难得的机会。终端地区冰层的持续增厚表明，这种进展将在未来几年继续下去。勘测观测记录了终点前方约200米处的冰前沉积物的同期变形，在压缩沉积物中形成了高达10米的突出凸起，上覆土壤和植被发生屈曲。主要研究人员将研究冰川末端前进的动力学，并调查这种前进对冰前地貌的影响。 表面速度，应变率，和表面海拔变化将被测量的冰川终点和冰川前的功能，沿着与终点位置的变化测量。将使用探地雷达和无线电回声探测来确定冰川的几何形状和河床的性质。他们将重复RES调查，以调查正在进行的冰下沉积物挖掘和战壕。探地雷达还将用于绘制冰前沉积物结构及其变形的三维图像。沉积物上现有的和新的标记将测量运动和应变。这项研究的一个主要特点是在几个月内使用精密的全球定位系统同时测量终端冰速和冰前沉积物的短期变化。端点动力学和物质平衡是冰川响应理论的组成部分，但人们对它们的了解很少。主要研究人员将使用有限元分析，以调查变形和应力场在终端冰楔和冰下和冰前沉积物，使用应变数据和几何形状作为约束。他们的目的是了解终端推进的详细动力学以及终端附近沉积物和冰的流变特性。他们还将使用我们持续的空中高度测量和表面高程的摄影测量来调查冰川增厚和终点前进之间的关系。