Measurements of superimposed ice formation and snow properties as a function of the surface energy balance during melt-onset are presented. They were performed on Kongsfjorden between May 20 and June 03 2002. Rapid snow melt occurred within 5 days and the snow cover initially 0.23 m thick transformed into 0.05 m to 0.06 m of superimposed ice. Melt-onset was characterized by rapid changes in the total energy balance, which became positive throughout the whole day after May 27. The increased energy fluxes were mainly caused by increases in incoming long-wave radiation due to overcast conditions.