We present and compare the dynamics (i.e., changes in standing stocks, saturation levels and concentrations) of O₂, Ar and N₂ in landfast sea ice, collected in Barrow (Alaska), from February through June 2009. The comparison suggests that the dynamic of O₂ in sea ice strongly depends on physical processes (gas incorporation and subsequent transport). Since Ar and N₂ are only sensitive to the physical processes in the present study, we then discuss the use of O₂ / Ar and O₂ / N₂ to correct for the physical contribution to O₂ supersaturations, and to determine the net community production (NCP). We conclude that O₂ / Ar suits better than O₂ / N₂, due to the relative abundance of O₂, N₂ and Ar, and the lower biases when gas bubble formation and gas diffusion are maximized. We further estimate NCP in the impermeable layers during ice growth, which ranged from −6.6 to 3.6 μmol O₂ L⁻¹ d⁻¹, and the concentrations of O₂ due to biological activity in the permeable layers during ice decay (3.8 to 122 μmol O₂ L⁻¹). We finally highlight the key issues to solve for more accurate NCP estimates in the future.