Subglacial processes and their control on ice dynamics and landscape evolution

该提案的目的是观察和量化机械过程和水文条件之间的强烈相互作用，目前在弱层状山谷冰川。 将在加拿大育空地区圣伊莱亚斯山脉的一个小山谷冰川进行实地研究，以确定冰川床的机械和水文条件。 将使用热水钻进入该床，并安装仪器阵列，以允许（1）借助冰下水力力学行为的数值模型解释现场记录，以及（2）使用数据来约束更一般的数值模型冰川动力学模型。 将通过重复钻孔测斜和全球定位系统测量技术测量冰的变形和表面流速，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。 仪器数据将用于改进冰下过程的解释模型，其长期目标是改进一般冰动力学模型对基底边界条件的处理。 基底过程对冰川行为的许多方面都有很大影响。 冰川下面是柔软的、可变形的沉积物，它们的移动是由冰变形、沉积物变形和基底滑动的某种组合引起的。 流动的最后两个组成部分通常统称为“基础运动”，并对冰团的运动有很大的贡献。 基底运动是某些冰川的主要流动机制，引起冰川的不稳定行为，并在冰盖的动力学和物质平衡中起着重要作用。 此外，冰层底部的有效侵蚀使冰川能够在山坡上雕刻出冰斗和山谷，并将大量沉积物输送到流域。 由于冰下高水压力促进冰川滑动和沉积物变形，基底运动受到冰川床水文条件的强烈影响。 因此，对基本过程的进一步了解是理解冰团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.