Gaseous elemental mercury (GEM, Hg°) was measured in the snowpack interstitial air on the Kongsvegen Glacier (Svalbard) between the surface and 190 cm depth. A rapid depletion of GEM from ∼5 to 0.4 ng.m−3 in the snowpack air was measured in less than 8 hours at a calculated depletion rate of ∼0.5–0.7 ng.m−3.h−1 while concentration of GEM above the snow stayed constant about 1.7 ng.m−3. This depletion could only be explained by chemical processes and this study suggests that Br. could be the most important reactant for the oxidation of GEM in the interstitial snow air. The lifetime of GEM was estimated to be ∼10 minutes with second order reaction rate constant between GEM and Br. of about ∼2 × 10−11 cm−3.molecule−1.s−1. These first experimental kinetic values for GEM oxidation in the snow air are in good agreement with both theoretical and modelling studies previously reported.