Glaciers flow under their own weight through a combination of viscous flow within the ice column and basal slip, which involves both sliding along and deformation within the bed. Deformable beds, made of unfrozen sediment, are prevalent and are often principal contributors to ice flow wherever we find them. Granular in nature, deformable beds have fascinating mechanical properties that depend on grain size distribution, porosity, and subglacial hydrology. Despite their importance for understanding glacier flow and the response of glaciers to changing climate, the mechanics of deformable glacier beds are not well understood.
Our general approach to understanding the mechanics of bed deformation and their effect on glacier flow is to acquire synoptic-scale, time-dependent observations of ice surface velocities and to use those observations to infer the mechanical properties of the bed via dynamical modeling. We take a natural laboratory approach, focusing on areas where changes in ice flow over time are due to known environmental forcings and where the processes of interest are mostly isolated from other effects. When necessary, we develop observational methods that involve the use of mapping radar systems.
Some relevant publications (Names of group members are bolded; * represents students, ^ postdocs)
M. Ranganathan*, B. M. Minchew, C. R. Meyer, and G. Hilmar Gudmundsson. A new approach to inferring basal drag and ice rheology in ice streams, with applications to West Antarctic ice streams. Journal of Glaciology, submitted, 2020.
B. M. Minchew and C. R. Meyer. Dilation of subglacial sediment governs incipient surge motion in glaciers with deformable beds. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, revised, 2020. [ pdf | doi ]
B. M. Minchew, M. Simons, B. V. Riel, and P. Milillo. Tidally induced variations in vertical and horizontal motion on Rutford Ice Stream, West Antarctica, inferred from remotely sensed observations. Journal of Geophysical Research - Earth Surface, 122:167-190, 2017. [ pdf | doi ]
B. M. Minchew, M. Simons, H. Björnsson, F. Pálsson, M. Morlighem, H. Seroussi, E. Larour, and S. Hensley. Plastic bed beneath Hofsjökull Ice Cap, central Iceland, and the sensitivity of ice flow to surface meltwater flux. Journal of Glaciology, 62(231):147-158, 2016. [ pdf | doi ]
B. M. Minchew, M. Simons, S. Hensley, H. Björnsson, and F. Pálsson. Early melt-season velocity fields of Langjökull and Hofsjökull ice caps, central Iceland. Journal of Glaciology, 61(226), 2015. [ pdf | doi ]