Determining the Influence of Lateral Margin Mechanical Properties on Glacial Flow

In glaciers and ice streams, resistance at the lateral margin plays a large role in ice velocity, yet these margins are often neglected when it comes to in-situ measurements of ice properties. With our current changing climate, it is more pertinent than ever to understand the impact that variations at the margins can have on glacial flow, for both understanding current ice flux and predicting how ice will behave in the future. Using Elmer/Ice, a full-Stokes, finite element, open-source modeling platform, we evaluate the sensitivity of ice flow to material parameters, including crystallographic orientation fabric and temperature, at the lateral margins of glaciers. Our sensitivity analysis is two-fold: 1) Jarvis Glacier, Alaska is used as a case study for model comparison and 2) synthetic geometries and parameters are combined to provide generalized conclusions regarding what conditions cause the most resistance.

In complementary work, we have measured the geometry and velocity of Jarvis Glacier, Alaska, as well as the thermal profile and fabric at two locations 25 m and 100 m from the margin. This access to realistic scenarios provides a baseline for which to analyze the subsequent sensitivity tests, allowing us to understand what parameters have the greatest impact on 3D glacial velocity, like fabric. Preliminary results of the synthetic geometries and parameters indicate fabric plays a larger role in resistance than temperature. When a 10 m boundary of isotropic fabric is assigned to an otherwise single-maximum glacier, flow decreases by 26% compared to a wholly single-maximum glacier. In the opposite case, when a 10 m, single-maximum boundary is assigned to an isotropic body, flow increases by 17%. When that boundary is extended farther into the glacier, flow can increase by 314%. Given the influence of parameters like fabric on the overall movement of the glacier, it is imperative we acquire enhanced measurements at the lateral margins of glaciers and ice streams to more accurately model and predict glacial flow.