The preservation of atmospheric nitrate in snow at Summit, Greenland

Abstract

There is great interest in using nitrate (NO3-) isotopic composition in ice cores to track the history of precursor nitrogen oxides (NOx = NO + NO2) in the atmosphere. NO 3-, however, can be lost from the snow by surface processes, such as photolysis back to NOx upon exposure to sunlight, making it difficult to interpret records of NO3- as a tracer of atmospheric NOx loading. In a campaign consisting of two field seasons (May-June) at Summit, Greenland, high temporal frequency surface snow samples were collected and analyzed for the oxygen isotopic composition of NO3-. The strong, linear relationship observed between the oxygen isotopes of NO3-, in both 2010 and 2011, is difficult to explain in the presence of significant postdepositional processing of NO3-, unless several unrelated variables change in concert. Therefore, the isotopic signature of NO3- in the snow at Summit is most feasibly explained as preserved atmospheric NO 3- deposition. Key Points Atmospheric nitrate is preserved in snow at Summit, Greenland Oxygen isotope results suggest stratospheric O3 influences nitrate formation A strong, linear relationship was found between 18-O and 17-O in nitrate ©2013. American Geophysical Union. All Rights Reserved.