The high-Alpine glacier saddle Colle Gnifetti (CG), Monte Rosa massif, is the only cold glacier archive in the European Alps o�ering detailed ice-core records on the millennial-scale. However, the highly irregular snow deposition pattern and the complex ow regime produce depositional noise and upstream e�ects, which hinder the full interpretation of the ice-core records in terms of past atmospheric changes. In this context, this work focuses on establishing a three-dimensional full Stokes ice- ow model of the CG saddle, with the main objective to calculate precise backward trajectories of existing ice-core sites, which is necessary to evaluate potential upstream e�ects. The developed full Stokes model is fully thermo-mechanically coupled and includes �rn rheology, �rn densi�cation and enthalpy transport, with consideration of atmospheric temperature changes of the last century, strain heating and surface meltwater refreezing. The simulations are performed using the state-of-the-art Finite Element software Elmer/Ice. The CG full Stokes model is validated by comparison with measurements of surface velocities, accumulation, annual layer thickness, borehole inclination angles, density and temperature. Estimated using di�erent bedrock topographies, the error of the calculated source point positions on the glacier surface amounts to �10% of the distance to the corresponding drill site. Moreover, the three-dimensional age �eld of the glacier is calculated with an uncertainty of �20%. The calculated chronologies of four out of �ve ice cores are consistent with experimental dating results, based among others on layer counting and 14C measurements.