Subglacial processes and their control on ice dynamics and landscape evolution

这项建议的目的是观察和量化软弱层状山谷冰川下存在的机械过程和水文条件之间的强烈相互作用。将在加拿大育空地区圣埃利亚斯山脉的一个小山谷冰川启动一项实地研究，以确定冰川床的力学和水文条件。由于将使用热水钻机进入冰床，将安装一系列仪器，以允许(1)借助冰下流体力学行为的数值模型来解释现场记录，以及(2)使用这些数据来约束更一般的冰川动力学数值模型。将通过重复的钻孔倾斜测量和GPS测量技术测量冰的变形和地表流量，根据自动气象站数据和积累/消融测量计算的融水产生率将有助于量化冰下排水系统特征的变化。这些仪器数据将用于改进冰下过程的解释模型。长期目标是改进一般冰动力学模型的基本边界条件的处理。基本过程对冰川行为的许多方面都有很大影响。被柔软、可变形的沉积物覆盖的冰川通过冰变形、沉积物变形和底部滑动的某种组合来移动。最后这两个流动分量通常统称为基本运动，对冰团的运动有很大贡献。基本运动是一些冰川的主要流动机制，导致潮水和汹涌的冰川的一些不稳定行为，并在冰盖的动力学和质量平衡中发挥重要作用。此外，冰层底部的有效侵蚀使冰川能够在山坡上划出圆圈和山谷，并将大量的沉积物输送到排水盆地。由于高冰川下水压促进了冰川滑动和沉积物变形，冰川床上的水文条件对基面运动有很大影响。因此，增进对基本过程的了解是理解冰块的动态行为及其对景观影响的关键。

The objective of this proposal is to observe and quantify the strong interaction between mechanical processes and hydrological conditions present beneath weak-bedded valley glaciers.  A field study will be initiated at a small valley glacier in the St. Elias Mountains of Yukon Territory, Canada to determine mechanical and hydrological conditions at the glacier bed.  The bed will be accessed using a hot-water drill, and arrays of instruments will be installed to allow (1) interpretation of field records with the aid of a numerical model of subglacial hydromechanical behaviours and (2) use of the data to constrain more general numerical models of glacier dynamics.  Ice deformation and surface flow rates will be measured by repeat borehole inclinometry and GPS survey techniques, and meltwater production rates calculated from automated weather station data and accumulation/ablation measurements will aid in quantifying changes in subglacial drainage system characteristics.  Instrument data will be used to improve an interpretation model of subglacial processes, with a long-term goal of improving the treatment of the basal boundary condition for general ice-dynamics models.   Basal processes greatly influence many aspects of glacier behaviour.  Glaciers that are underlain by soft, deformable sediments move by some combination of ice deformation, sediment deformation and basal sliding.  These last two components of flow are often collectively called "basal motion" and can contribute greatly to the motion of ice masses.  Basal motion is the dominant flow mechanism of some glaciers, gives rise to some unstable behaviours of tidewater and surging glaciers and plays an important role in the dynamics and mass balance of ice sheets.  In addition, effective erosion at the base of the ice allows glaciers to carve cirques and valleys into mountainsides and to deliver vast quantities of sediment to drainage basins.  Because high subglacial water pressures facilitate both glacier sliding and sediment deformation, basal motion is strongly influenced by hydrological conditions at the glacier bed.  An improved knowledge of basal processes is thus key to understanding both the dynamic behaviour of ice masses and their effect on the landscape.