The role of tributaries in glacier surges

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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.