AbstractAs a major sink of atmospheric nitrogen oxides (NOx = NO + NO2), nitrate (NO3−) in polar snow can reflect the long‐range transport of NOx and related species (e.g., peroxyacetyl nitrate). On the other hand, because NO3− in snow can be photolyzed, potentially producing gas phase NOx locally, NO3− in snow (and thus, ice) may reflect local processes. Here we investigate the relationship between local atmospheric composition at Summit, Greenland (72°35′N, 38°25′W) and the isotopic composition of NO3− to determine the degree to which local processes influence atmospheric and snow NO3−. Based on snow and atmospheric observations during May–June 2010 and 2011, we find no connection between the local atmospheric concentrations of a suite of gases (BrO, NO, NOy, HNO3, and nitrite (NO2−)) and the NO3− isotopic composition or concentration in snow. This suggests that (1) the snow NO3− at Summit is primarily derived from long‐range transport and (2) this NO3− is largely preserved in the snow. Additionally, three isotopically distinct NO3− sources were found to be contributing to the NO3− in the snow at Summit during both 2010 and 2011. Through the complete isotopic composition of NO3−, we suggest that these sources are local anthropogenic particulate NO3− from station activities (δ15N = 16‰, Δ17O = 4‰, and δ18O = 23‰), NO3− formed from midlatitude NOx (δ15N = −10‰, Δ17O = 29‰, δ18O = 78‰) and a NO3− source that is possibly influenced by or derived from stratospheric ozone NO3− (δ15N = 5‰, Δ17O = 39‰, δ18O = 100‰).
