News Release 

New 'law' to explain how glaciers flow over soft ground

American Association for the Advancement of Science

Addressing a major source of uncertainty in glacier-flow models, researchers present a new slip law to describe glaciers sliding on soft, deformable material. The findings may help create a universal slip law that could be used to constrain the models of the glaciers and ice sheets that could have the greatest potential impacts on global sea-level rise. Glaciers slip, slide and surge over a wide variety of terrain, ranging from solid bedrock (hard-bedded) to loose gravel-like sediments (soft-bedded). Friction, velocity and water pressure at the ice-bed interface beneath the glacier are all well-known factors that determine a glacier's movement and are used to inform glacier-flow models. However, accounting for these factors in relation to the material underlying the moving ice in models has been difficult. This is particularly true for many of the fast-flowing, marine terminating glaciers in Antarctica and Greenland that rest on deformable till. Because of this, many soft-bedded glaciers and ice sheets are imperfectly modeled, including the West Antarctic Ice Sheet. As a result, they often represent the largest source of uncertainty in estimations for future sea-level rise. Thus, it is critically important to better understand and parameterize glacier movement. Lucas Zoet and Neal Iverson designed an experimental physical model to determine the processes that govern glacier slip over water-saturated till to derive a new slip law for soft-bedded glaciers. Zoet and Iverson discovered that, despite differences in the physical mechanisms themselves, their soft-bedded slip law works both in the case of bed deformation and bed shear. When combined with parameterization for hard beds, the results create a generalized slip law for glacier-flow models.

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