We have reconstructed the ice thickness distribution of the Morteratsch glacier complex,
Switzerland, and used this to simulate its flow with a higher-order 3-D model. Ice thickness was
measured along transects with a ground-penetrating radar and further extended over the entire glacier
using the plastic flow assumption and a distance-weighted interpolation technique. We find a maximum
ice thickness of 35052.5m for the central trunk of Vadret da Morteratsch, resulting from a bedrock
overdeepening. The average thickness of the glacier complex is 72.218.0 m, which corresponds to a
total ice volume of 1.140.28km3. The flow of the glacier is modelled by tuning the rate factor and the
sliding parameters taking into account higher-order terms in the force balance. The observed velocities
can be reproduced closely (root-mean-square error of 15.0ma–1, R2 = 0.93) by adopting a sliding factor
of 1210–16m7N–3 a–1 and a rate factor of 1.610–16 Pa–3 a–1. In this setting, ice deformation accounts
for 70% of the surface velocity and basal sliding for the remaining 30%. The modelled velocity field
reaches values up to 125ma–1, but also indicates an almost stagnant front and confluence area, which
are crucial for understanding the ongoing glacier retreat.