The role of tributaries in glacier surges

冰川涌动的特征是速度突然增加一到两个数量级，并经常导致冰川末端的显著移动。虽然冰下水力在涌浪中的作用已经有了很好的记录，但涌浪的启动问题仍然没有得到解决。此外，为什么一些冰川涌动而另一些冰川不涌动的相关问题仍然悬而未决。这项提议将调查许多阿拉斯加山脉冰川的特殊几何形状是否允许产生特别大的剪应力，从而最终允许涌流发生。拟议的工作将集中在阿拉斯加东部德纳利断层上的黑色急流冰川上。研究人员认为，了解冰川涌动也有助于了解冰川的基本边界条件，这仍然是冰川学中的一个主要问题。随着冰流的数值模式变得越来越复杂，基本边界条件的问题将不得不重新讨论，理解导致从静止到激增的强烈非线性方面是很重要的。从启动浪涌中吸取的经验教训也可应用于冰在高应力条件下快速流动的其他情况，例如在快速出口冰川。实地工作将包括准确绘制冰川底部地图的雷达，生成冰川表面全数字海拔模型的机载激光雷达，冰速的GPS测量，用于气候数据和冰消融的气象站，以及监测边缘湖泊排水的相机。这些观测结果将与冰川的三维流动模型完全结合，并得到补充。拟议的工作将形成博士论文的核心，并接受现场方法、数据分析和数值建模方面的培训。科学成果将在国家和国际会议上提出，并以同行评议的文献形式发表。由于冰川研究往往会吸引公众的极大兴趣，而黑色急流对许多阿拉斯加人来说也很熟悉，所以这个项目非常适合公众宣传。外展工作将通过该研究所的新闻办公室进行协调，该办公室定期安排出席人数众多的公开讲座，并提供有关该研究所科学活动的新闻专栏。

A glacier surge is characterized by a sudden increase in speed by one to two orders of magnitude and often leads to a significant movement of the terminus of the glacier. While the role of subglacial hydraulics during the surge has been well documented, the issue of surge initiation has remained unsolved. Also, the related question of why some glaciers surge and others do not remains open. This proposal will investigate whether the special geometry of many Alaska Range glaciers allows particularly large shear stresses to develop that eventually allow a surge to occur. The proposed work would focus on the Black Rapids Glacier on the Denali Fault in the eastern Alaska Range. The investigators contend that understanding glacier surges can also make a fundamental contribution to understanding of the basal boundary condition, which remains a major question in glaciology. As numerical models of ice flow are becoming more sophisticated, the issue of the basal boundary condition will have to be revisited and it is important to understand the strong non-linear aspects that lead to the switch from quiescence to surge. Lessons learned from surge initiation can also be applied to other situations where ice flows fast under high stress conditions, such as at fast outlet glaciers. The fieldwork would include radar to accurately map the base of the glacier, airborne lidar to generate a full digital elevation model of the surface of the glacier, GPS measurements of ice velocity, meteorological stations for climate data and ice ablation, and cameras to monitor the marginal lakes for drainage. These observations will be fully integrated with and complemented by a three-dimensional flow model of the glacier. The proposed work would form the core of a PhD thesis with training in field methods, data analysis, and numerical modeling. Scientific results will be presented at national and international meetings and in the peer-reviewed literature. Because glacier research tends to attract great interest among the general public, and Black Rapids is familiar to many Alaskans, this project is well-suited to public outreach. Outreach efforts will be coordinated through the institute's Information Office, which regularly schedules well-attended public talks and provides news columns about the institute's science activities.