Anomalous nitrate concentrations in polar ice cores—Do they result from solar particle injections into the polar atmosphere?

Nitrate concentrations and electrical conductivity in an ice core from central Greenland have been measured simultaneously on 1.5 cm sections along the entire length of the 122 m core. This method of micro-resolution (time resolution is 1 week-1 month) provides for statistically significant determinations of rapid variations in nitrate fallout from the polar stratosphere superimposed on a background from all other sources. The seasonal NO3− background variations and the volcanic signal contained in the electrical conductivity data provide accurate dating of the ice core. This type of micro-resolution nitrate measurement appears to be useful as a tool to investigate the possible sources of polar nitrate anomalies such as solar proton events.