GLOBAL PERSPECTIVE OF NITRATE FLUX IN ICE CORES

The relationships between the concentration and the flux of chemical s pecies (Cl-, NO3-, SO42-, Na+, K+, NH4+, Mg2+, Ca2+) versus snow accum ulation 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. A t all sites, only nitrate flux is significantly (alpha = 0.05) related to snow accumulation rate. Of all the chemical series, only nitrate c oncentration 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. T he 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 NOx released from peroxyacetyl nitrate by thermal decompositio n in the presence of higher OH concentrations in summer. The late wint er/early spring nitrate peak observed in modern Greenland snow may be related to the buildup of anthropogenically derived NOy in the Arctic troposphere during the long polar winter.