Reconstructions of the past variations of atmospheric composition are important for better understanding of the changes in climate and atmospheric chemistry. The data from direct atmospheric observations of various trace gas mole fractions and isotope ratios have become available over the last few decades. The analyses of air bubbles in polar ice cores have provided those from the pre-industrial era to the mid-20th century. Old air is also found in porous snow layers (firn) on top of polar ice sheets, because the gas movements in firn occur mainly by molecular diffusion. Depth profiles of firn air components are therefore useful for bridging the records from direct observations and ice-core analyses (covering up to about a century). The firn air data are also helpful for constraining firn air transport models toward better understanding of snow densification and interpretation of ice core data. Here we present the depth profiles of air composition in the firn at the North Greenland Ice Core Project (NGRIP) site. Various gas components, including atmospheric O2/N2 ratio, greenhouse gases, halocarbons and their isotope ratios, were measured from air samples collected from the NGRIP firn by using combination of high-precision measurement systems. The data are presented in a spreadsheet format (.xlsx).
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