Measurements and Modeling of the Internal Ice Deformation of an Alpine Glacier: Unteraargletscher, Switzerland

 

The total forward motion of glaciers can be divided into internal ice deformation and basal motion. An understanding of both modes of motion is crucial to our ability to model the flow behavior of glaciers. The internal ice deformation is described with a flow law relating strain rate to stress. The basal motion comprises basal sliding and bed deformation and is usually described in flow models using a sliding law relating basal motion and basal shear stress.

Recent improvements in flow modeling and field observation techniques have made it increasingly feasible to use in-situ measurements of ice deformation in a combination with stress solutions based on advanced flow models to study the flow law of ice. The goal of the study is to use inverse modeling of measurements of internal ice deformation and surface velocities to test hypotheses for the flow law of temperate ice, and to validate theoretical concepts about glacier flow.

The deformation of a borehole on Unteraargletscher was measured with an inclinometer probe. The diffusion of the medial moraine, representing a prominent surface undulation, was surveyed using differential GPS equipment. This dataset, in combination with a highly sophisticated three-dimensional finite element glacier flow model, allows to study the flow behavior of temperate ice at both, high stresses (controlling the internal deformation and the horizontal surface velocities) and low stresses (driving the vertical and transverse velocities at the surface).