Model simulations were carried out using GEM-MACH, with implementation of bromine chemistry and a representation of Arctic snowpack bromine source mechanism, to assess the model’s ability in capturing the Arctic boundary-layer O3 seasonal cycle. The study demonstrated the important influence of the bromine mediated ODEs on the seasonal cycle of boundary-layer O3 in the High Arctic. Through model sensitivity simulations, we show that atmospheric aerosols play an important role in contributing to the Arctic springtime ODEs at higher altitudes and farther downwind from the bromine source areas.