  The friction coefficient and the base topography of a stationary and a
dynamic ice sheet are perturbed in two models for the ice: the full Stokes
equations and the shallow shelf approximation. The sensitivity to the
perturbations of the velocity and the height at the surface is quantified by
solving the adjoint equations of the stress and the height equations providing
weights for the perturbed data. The adjoint equations are solved numerically
and the sensitivity is computed in several examples in two dimensions.
Comparisons are made with analytical solutions to simplified problems.
