Measurement and simulation of snow and superimposed ice at the Kongsvegen glacier, Svalbard (Spitzbergen)

Multiyear glaciometeorological data have been collected at about the equilibrium line of Kongsvegen glacier in Svalbard. During the first summer of the investigation period, about 0.6 m of superimposed ice (SI) was built up because of effective meltwater refreeze upon the former glacier surface. Thus winter accumulation is completely retained from runoff, and latent heat is released equivalent to 27% of July net radiation. This ice layer, as well as part of the former year's ice, disappeared during the subsequent summer. Using a physically based snow model, the evolution of the snow pack properties as well as the observed amount of SI is successfully reproduced. However, the latter is only possible by modifying the model's water transport routine to also treat effects of ponding water, which have been observed. Two distinct phases of SI formation can be distinguished. A first one (15 cm) is initiated as soon as meltwater has penetrated to the underlying cold glacier ice. Toward the end of the melt period, however, the remaining body of SI is rapidly formed because of intense atmospheric cooling. The availability of ponding water plays an essential role in this context. During the following summer the initial refreezing phase was terminated by exposure of the newly built SI at the surface. The whole amount of the actual year and the major part of the former year's SI was melted then. A positive ice‐albedo feedback process plays an additional role there. Sensitivity studies prove that the model results and their interpretation do not critically depend on possible uncertainties of input data and model parameters. Despite their local nature these studies are valuable steps toward understanding the regional distribution of SI on Arctic glaciers as well as their climate sensitivity. Remote sensing studies indicate that SI presently covers 35% of Kongsvegen's surface area.