Greenland Summit 2013 Firn Air Results

This data set contains measurements of 14C in CO2, CO and CH4 in firn air sampled at Greenland Summit. The main feature in the Δ14C of CO2 data is an increase with depth that reflects a smoothed atmospheric Δ14C of CO2 history. The highest Δ14C of CO2 value at 80.06 m sampling depth approximately coincides with the atmospheric 14C “bomb peak”, with signal smoothing from firn gas diffusion, as for other samples. The concentration of 14C of CO shows relatively little change in the upper part of the firn (0 - 68 m), and increases strongly in the lock-in zone (68 - 80 m). This increase is driven by the accumulation of in situ cosmogenic 14CO in air in the firn lock-in zone. 14C of CH4 also shows relatively little change in the upper part of the firn (0 - 68m), reflecting relatively stable 14C of CH4 values in the atmosphere in the decade preceding sampling. 14C of CH4 declines with depth in the firn lock-in zone, reflecting lower 14C of CH4 values in the atmosphere going further back in time. This decline is mainly caused by lower 14CH4 emissions from nuclear power plants further back in time.