Response of Different Antarctic Outlet Glacier Types to Perturbations at Their Boundaries

Abstract:

Ice sheets are primarily drained by outlet glaciers and ice streams that transport mass from the inland to the ocean. Determining mass loss from the ice sheets is particularly important for calculating future sea level rise. Currently, dynamic ice loss is not included in the prediction of future sea levels, due to the uncertain response of outlet glaciers to climatic perturbations. It is therefore crucial to understand how different types of glaciers respond to changes at their boundaries.

Outlet glaciers can be categorized based on their geometry and the mechanisms that drive fast flow. Ice streams are wide with a small surface slope, flow fast despite low driving stress and have little basal drag. Isbrae on the other hand are narrow with a steep surface slope and large driving stress. Between these two end members fall a variety of mixed-type glaciers.

We investigate the response of different types of Antarctic outlet glaciers to perturbation scenarios with a flow line model. The effect of reduction in basal drag due to increased sliding, changes in surface accumulation, an increase in submarine melting around the grounding zone, a lower back force at the terminus, and a decrease in lateral drag on glacier stability are explored. 

Preliminary results indicate that a short-term increase in basal sliding (e.g. from lake discharge events), or increased surface accumulation rates have little impact on the ice flow and the glacier's stability, whereas ice shelf thinning or a reduction in back force result in an immediate response of the outlet glacier. In these cases, a new stable position with an increased but constant ice discharge is obtained soon.