<jats:title>Abstract</jats:title><jats:p>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 350 ±52.5 m for the central trunk of Vadret da Morteratsch, resulting from a bedrock overdeepening. The average thickness of the glacier complex is 72.2 ±18.0 m, which corresponds to a total ice volume of 1.14 ± 0.28 km<jats:sup>3</jats:sup>. 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 15.0 m a<jats:sup>-1</jats:sup>, <jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.93) by adopting a sliding factor of 12 x 10–<jats:sup>16</jats:sup> m<jats:sup>7</jats:sup> N–<jats:sup>3</jats:sup> a<jats:sup>-1</jats:sup> and a rate factor of 1.6 x 10-16 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 125 ma<jats:sup>-1</jats:sup>, but also indicates an almost stagnant front and confluence area, which are crucial for understanding the ongoing glacier retreat.</jats:p>