Global perspective of nitrate flux in ice cores

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Abstract
The relationships between the concentration and the flux of chemical species (Cl−, NO3−, SO42−, Na+, K+, NH4+, Mg2+, Ca2+) versus snow accumulation rate were examined at GISP2 and 20D in Greenland, Mount Logan from the St. Elias Range, Yukon Territory, Canada, and Sentik Glacier from the northwest end of the Zanskar Range in the Indian Himalayas. At all sites, only nitrate flux is significantly (α = 0.05) related to snow accumulation rate. Of all the chemical series, only nitrate concentration data are normally distributed. Therefore we suggest that nitrate concentration in snow is affected by postdepositional exchange with the atmosphere over a broad range of environmental conditions. The persistent summer maxima in nitrate observed in Greenland snow over the entire range of record studied (the last 800 years) may be mainly due to NOxreleased from peroxyacetyl nitrate by thermal decomposition in the presence of higher OH concentrations in summer. The late winter/early spring nitrate peak observed in modern Greenland snow may be related to the buildup of anthropogenically derived NOyin the Arctic troposphere during the long polar winter.