We used a snow photochemistry model (TRANSITS) to simulate the seasonal nitrate snow profile at Summit, Greenland. Comparisons between model outputs and observations suggest that at Summit post-depositional processing is active and probably dominates the snowpack δ¹⁵N seasonality. We also used the model to assess the degree of snow nitrate loss and the consequences in its isotopes at present and in the past, which helps for quantitative interpretations of ice-core nitrate records.