Modeling the grounding line dynamics of Thwaites Glacier, West Antarctica using full Stokes and lower order models

Thwaites Glacier (TG) is one of the largest ice streams in West Antarctica and the broadest (about 110 km wide). Satellite observations have revealed that the grounding line is retreating rapidly, ice is thinning meters per year, the fast portion of the ice stream is widening, and since 2006 the main portion of the glacier has been accelerating following a period of relatively steady speed.

Here, we use the JPL/UCI Ice Sheet System Model (ISSM) to study the grounding line dynamics of Thwaites Glacier to determine its stability and sensitivity to changes in ice-ocean interactions. We use a full Stokes model, a higher order (HO) approximation and a shelfy-stream approximation (SSA) in 2D and try to best fit observations of ice flow, ice surface elevation and ice thickness across the grounding line by tuning basal friction on land and bottom melt rates on the floating ice tongue. The motion of the grounding line is treated as a contact problem with Full Stokes and using hydrostatic equilibrium with HO and SSA. We show that only the Full Stokes model can correctly represent the balance of stresses and a near steady state profile of the glacier across the grounding line. The work is then extended in 3D to estimate the sensitivity of the glacier’s grounding line to changes in ice melt rates.