Composition of firn air at the North Greenland Ice Core Project (NGRIP) site

Reconstructions of the past variations of atmospheric composition are important for better understanding of the changes of climate and atmospheric chemistry. While direct observations of atmospheric composition and isotope ratios are currently available, ice core analyses revealed those in the pre-industrial era. Porous compacted snow layers (firn) over ice sheets also archive air up to 100 years older than that at surface. Depth profiles from firn air measurements are therefore useful for reconstructing historical variations of trace gas species over times about century back in time. They are also helpful for improving firn air transport models toward better understanding of snow densification and interpretation of ice core data. Here we present depth profiles of air composition in the firn at a Greenland site of NGRIP (North Greenland Ice Core Project). Various greenhouse gases, halocarbons and isotope ratios were analyzed from air samples collected from the NGRIP firn by using combination of high-precision measurement systems.