Land ice forms an important component of the climate system. Sea level variations are closely related to the total ice volume. However, the relation between glacier mass balance and meteorological conditions is inderstood only broadly. In particular, the strong variation of mass balance patterns on the 10-300 km scale has hardly been investigated. Reduction of the uncertainty in estimating changes in glacier mass balance for climate change scenario's requires a better knowledge of the processes that lead to the spatial variability of glacier mass balance. The goal of the project is to indentify and model the most important factors leading to mesoscale variability of the mass balance field on ice caps.